Microwave wave range. Features of the construction of microwave technology

The content of the article

ULTRA HIGH FREQUENCY RANGE, frequency range of electromagnetic radiation (100-300,000 million hertz), located in the spectrum between ultra-high television frequencies and frequencies of the far infrared region. This frequency range corresponds to wavelengths from 30 cm to 1 mm; therefore it is also called the decimeter and centimeter wave range. In English-speaking countries it is called the microwave band; This means that the wavelengths are very small compared to the wavelengths of conventional radio broadcasting, which are on the order of several hundred meters.

Since microwave radiation is intermediate in wavelength between light radiation and ordinary radio waves, it has some properties of both light and radio waves. For example, like light, it travels in a straight line and is blocked by almost all solid objects. Much like light, it is focused, spreads out as a beam, and reflected. Many radar antennas and other microwave devices are enlarged versions of optical elements such as mirrors and lenses.

At the same time, microwave radiation is similar to radio radiation in the broadcast ranges in that it is generated by similar methods. The classical theory of radio waves applies to microwave radiation, and it can be used as a means of communication based on the same principles. But thanks to higher frequencies, it provides greater opportunities for transmitting information, which makes communication more efficient. For example, one microwave beam can carry several hundred telephone conversations simultaneously. The similarity of microwave radiation to light and the increased density of information it carries have proven to be very useful for radar and other fields of technology.

APPLICATION OF MICROWAVE RADIATION

Radar.

Waves in the decimeter-centimeter range remained a subject of purely scientific curiosity until the outbreak of World War II, when there was an urgent need for a new and effective electronic means of early detection. Only then did intensive research into microwave radar begin, although its fundamental possibility was demonstrated back in 1923 at the US Naval Research Laboratory. The essence of radar is that short, intense pulses of microwave radiation are emitted into space, and then part of this radiation is recorded, returning from the desired distant object - a sea vessel or aircraft.

Connection.

Microwave radio waves are widely used in communications technology. In addition to various military radio systems, there are numerous commercial microwave communication lines in all countries of the world. Since such radio waves do not follow the curvature of the earth's surface but travel in a straight line, these communication links typically consist of relay stations installed on hilltops or radio towers at intervals of approx. 50 km. Parabolic or horn antennas mounted on towers receive and transmit microwave signals. At each station, the signal is amplified by an electronic amplifier before retransmission. Since microwave radiation allows highly targeted reception and transmission, transmission does not require large amounts of electricity.

Although the system of towers, antennas, receivers and transmitters may seem very expensive, in the end it all more than pays off thanks to the large information capacity of microwave communication channels. Cities across the United States are connected by a complex network of more than 4,000 microwave relay links, forming a communications system that stretches from one ocean coast to the next. The channels of this network are capable of transmitting thousands of telephone conversations and numerous television programs simultaneously.

Communications satellites.

The system of radio relay towers necessary for transmitting microwave radiation over long distances can, of course, only be built on land. For intercontinental communication, a different relay method is required. Here, connected artificial earth satellites come to the rescue; launched into geostationary orbit, they can perform the functions of microwave communication relay stations.

An electronic device called an active-relay satellite receives, amplifies, and relays microwave signals transmitted by ground stations. The first experimental satellites of this type (Telstar, Relay and Syncom) successfully relayed television broadcasts from one continent to another in the early 1960s. Based on this experience, commercial intercontinental and domestic communications satellites were developed. Intelsat's latest intercontinental series satellites have been launched into different locations in geostationary orbit in such a way that their coverage areas overlap to provide service to subscribers around the world. Each Intelsat satellite of the latest modifications provides customers with thousands of high-quality communication channels for the simultaneous transmission of telephone, television, fax signals and digital data.

Heat treatment of food products.

Microwave radiation is used for heat treatment of food products at home and in the food industry. The energy generated by high-power vacuum tubes can be concentrated into a small volume for highly efficient thermal processing of products in the so-called. microwave or microwave ovens, characterized by cleanliness, noiselessness and compactness. Such devices are used in aircraft galleys, railway dining cars and vending machines, where quick food preparation and cooking are required. The industry also produces microwave ovens for household use.

Scientific research.

Microwave radiation has played an important role in studies of the electronic properties of solids. When such a body finds itself in a magnetic field, free electrons in it begin to rotate around magnetic field lines in a plane perpendicular to the direction of the magnetic field. The rotation frequency, called the cyclotron frequency, is directly proportional to the magnetic field strength and inversely proportional to the effective mass of the electron. (The effective mass determines the acceleration of an electron under the influence of some force in the crystal. It differs from the mass of a free electron, which determines the acceleration of the electron under the influence of some force in a vacuum. The difference is due to the presence of attractive and repulsive forces that act on the electron in the crystal surrounding atoms and other electrons.) If microwave radiation falls on a solid body located in a magnetic field, then this radiation is strongly absorbed when its frequency is equal to the cyclotron frequency of the electron. This phenomenon is called cyclotron resonance; it allows one to measure the effective mass of an electron. Such measurements have provided much valuable information about the electronic properties of semiconductors, metals, and metalloids.

Microwave radiation also plays an important role in space research. Astronomers have learned a lot about our Galaxy by studying the 21 cm wavelength emitted by hydrogen gas in interstellar space. It is now possible to measure the speed and direction of movement of the galaxy's arms, as well as the location and density of regions of hydrogen gas in space.

SOURCES OF MICROWAVE RADIATION

Rapid progress in the field of microwave technology is largely associated with the invention of special vacuum devices - magnetron and klystron, capable of generating large amounts of microwave energy. A generator based on a conventional vacuum triode, used at low frequencies, turns out to be very ineffective in the microwave range.

The two main disadvantages of the triode as a microwave generator are the finite time of flight of the electron and the interelectrode capacitance. The first is due to the fact that it takes an electron some (albeit short) time to fly between the electrodes of a vacuum tube. During this time, the microwave field manages to change its direction to the opposite direction, so that the electron is forced to turn back before reaching the other electrode. As a result, electrons oscillate inside the lamp without any benefit, without giving up their energy to the oscillatory circuit of the external circuit.

Magnetron.

The magnetron, invented in Great Britain before World War II, does not have these disadvantages, since it is based on a completely different approach to the generation of microwave radiation - the principle of a volumetric resonator. Just as an organ pipe of a given size has its own acoustic resonance frequencies, a cavity resonator has its own electromagnetic resonances. The walls of the resonator act as inductance, and the space between them acts as the capacitance of a certain resonant circuit. Thus, a cavity resonator is similar to a parallel resonant circuit of a low-frequency oscillator with a separate capacitor and inductor. The dimensions of the cavity resonator are chosen, of course, so that the desired resonant ultra-high frequency corresponds to a given combination of capacitance and inductance.

The magnetron (Fig. 1) has several volumetric resonators located symmetrically around the cathode located in the center. The device is placed between the poles of a strong magnet. In this case, the electrons emitted by the cathode are forced to move along circular trajectories under the influence of a magnetic field. Their speed is such that at a strictly defined time they cross the open grooves of the resonators at the periphery. At the same time, they give off their kinetic energy, exciting vibrations in the resonators. The electrons are then returned to the cathode and the process repeats. Thanks to this device, the time of flight and interelectrode capacitances do not interfere with the generation of microwave energy.

Magnetrons can be made large, and then they produce powerful pulses of microwave energy. But the magnetron has its drawbacks. For example, resonators for very high frequencies become so small that they are difficult to manufacture, and such a magnetron itself, due to its small size, cannot be powerful enough. In addition, a magnetron requires a heavy magnet, and the required magnet mass increases with increasing power of the device. Therefore, powerful magnetrons are not suitable for aircraft on-board installations.

Klystron.

This electric vacuum device, based on a slightly different principle, does not require an external magnetic field. In a klystron (Fig. 2), electrons move in a straight line from the cathode to the reflective plate, and then back. In doing so, they cross the open gap of the donut-shaped cavity resonator. The control grid and resonator grids group electrons into separate “clumps” so that electrons cross the resonator gap only at certain times. The gaps between the bunches are matched to the resonant frequency of the resonator in such a way that the kinetic energy of the electrons is transferred to the resonator, as a result of which powerful electromagnetic oscillations are established in it. This process can be compared to the rhythmic swinging of an initially motionless swing.

The first klystrons were rather low-power devices, but later they broke all records of magnetrons as high-power microwave generators. Klystrons were created that delivered up to 10 million watts of power per pulse and up to 100 thousand watts in continuous mode. The klystron system of the research linear particle accelerator produces 50 million watts of microwave power per pulse.

Klystrons can operate at frequencies up to 120 billion hertz; however, their output power, as a rule, does not exceed one watt. Design options for a klystron designed for high output powers in the millimeter range are being developed.

Klystrons can also serve as amplifiers for microwave signals. To do this, you need to apply an input signal to the grids of the cavity resonator, and then the density of the electron bunches will change in accordance with this signal.

Traveling wave lamp (TWT).

Another electrovacuum device for generating and amplifying electromagnetic waves in the microwave range is a traveling wave lamp. It consists of a thin evacuated tube inserted into a focusing magnetic coil. There is a retarding wire coil inside the tube. An electron beam passes along the axis of the spiral, and a wave of the amplified signal runs along the spiral itself. The diameter, length and pitch of the spiral, as well as the speed of the electrons, are selected in such a way that the electrons give up part of their kinetic energy to the traveling wave.

Radio waves travel at the speed of light, while the speed of electrons in the beam is much slower. However, since the microwave signal is forced to travel in a spiral, its speed along the tube axis is close to the speed of the electron beam. Therefore, the traveling wave interacts with electrons for a long time and is amplified, absorbing their energy.

If no external signal is applied to the lamp, then random electrical noise at a certain resonant frequency is amplified and the traveling wave TWT operates as a microwave generator rather than an amplifier.

The output power of a TWT is significantly less than that of magnetrons and klystrons at the same frequency. However, TWTs can be tuned over an unusually wide frequency range and can serve as very sensitive low-noise amplifiers. This combination of properties makes the TWT a very valuable device in microwave technology.

Flat vacuum triodes.

Although klystrons and magnetrons are preferred as microwave oscillators, improvements have somewhat restored the important role of vacuum triodes, especially as amplifiers at frequencies up to 3 billion hertz.

Difficulties associated with time of flight are eliminated due to the very short distances between the electrodes. Unwanted interelectrode capacitance is minimized because the electrodes are mesh and all external connections are made on large rings located outside the lamp. As is customary in microwave technology, a volumetric resonator is used. The resonator tightly encloses the lamp, and ring connectors provide contact along the entire circumference of the resonator.

Gunn diode generator.

Such a semiconductor microwave generator was proposed in 1963 by J. Gunn, an employee of the Watson Research Center of the IBM Corporation. Currently, such devices provide power of only the order of milliwatts at frequencies of no more than 24 billion hertz. But within these limits it has undoubted advantages over low-power klystrons.

Since the Gunn diode is a single crystal of gallium arsenide, it is in principle more stable and durable than a klystron, which must have a heated cathode to create a flow of electrons and requires a high vacuum. In addition, a Gunn diode operates at a relatively low supply voltage, whereas powering a klystron requires bulky and expensive power supplies with voltages ranging from 1000 to 5000 V.

CIRCUIT COMPONENTS

Coaxial cables and waveguides.

To transmit electromagnetic waves in the microwave range not through the ether, but through metal conductors, special methods and specially shaped conductors are needed. Conventional wires that carry electricity, suitable for transmitting low-frequency radio signals, are ineffective at ultra-high frequencies.

Any piece of wire has capacitance and inductance. These so-called distributed parameters are becoming very important in microwave technology. The combination of the conductor's capacitance with its own inductance at ultra-high frequencies plays the role of a resonant circuit, almost completely blocking transmission. Since it is impossible to eliminate the influence of distributed parameters in wired transmission lines, we have to turn to other principles for transmitting microwave waves. These principles are embodied in coaxial cables and waveguides.

A coaxial cable consists of an inner conductor and a cylindrical outer conductor surrounding it. The gap between them is filled with a plastic dielectric, such as Teflon or polyethylene. At first glance, this may seem similar to a pair of ordinary wires, but at ultrahigh frequencies their function is different. A microwave signal introduced from one end of the cable actually propagates not through the metal of the conductors, but through the gap between them filled with insulating material.

Coaxial cables are good at transmitting microwave signals up to several billion hertz, but at higher frequencies their efficiency decreases and they are unsuitable for transmitting high powers.

Conventional channels for transmitting microwave waves are in the form of waveguides. A waveguide is a carefully machined metal tube with a rectangular or circular cross-section, inside which a microwave signal propagates. Simply put, the waveguide directs the wave, causing it to be reflected from the walls every now and then. But in fact, the propagation of a wave along a waveguide is the propagation of oscillations of the electric and magnetic fields of the wave, as in free space. Such propagation in a waveguide is possible only if its dimensions are in a certain relationship with the frequency of the transmitted signal. Therefore, the waveguide is precisely calculated, processed precisely and intended only for a narrow frequency range. It transmits other frequencies poorly or not at all. A typical distribution of electric and magnetic fields inside a waveguide is shown in Fig. 3.

The higher the frequency of the wave, the smaller the dimensions of the corresponding rectangular waveguide; in the end, these dimensions turn out to be so small that its manufacture becomes excessively complicated and the maximum power transmitted by it is reduced. Therefore, the development of circular waveguides (circular cross-section) has begun, which can be quite large in size even at high frequencies in the microwave range. The use of a circular waveguide is hampered by some difficulties. For example, such a waveguide must be straight, otherwise its efficiency is reduced. Rectangular waveguides are easy to bend; they can be given the desired curvilinear shape, and this does not affect signal propagation in any way. Radar and other microwave installations usually look like intricate labyrinths of waveguide paths connecting different components and transmitting the signal from one device to another within the system.

Solid state components.

Solid-state components, such as semiconductors and ferrites, play an important role in microwave technology. Thus, germanium and silicon diodes are used to detect, switch, rectify, frequency convert and amplify microwave signals.

For amplification, special diodes are also used - varicaps (with controlled capacitance) - in a circuit called a parametric amplifier. Widespread amplifiers of this kind are used to amplify extremely small signals, since they introduce almost no noise or distortion of their own.

A ruby ​​maser is also a solid-state microwave amplifier with a low noise level. Such a maser, whose operation is based on quantum mechanical principles, amplifies the microwave signal due to transitions between the internal energy levels of atoms in a ruby ​​crystal. The ruby ​​(or other suitable maser material) is immersed in liquid helium so that the amplifier operates at extremely low temperatures (only a few degrees above absolute zero). Therefore, the thermal noise level in the circuit is very low, making the maser suitable for radio astronomy, ultra-sensitive radar and other measurements where extremely weak microwave signals need to be detected and amplified.

Ferrite materials such as magnesium iron oxide and yttrium iron garnet are widely used for the manufacture of microwave switches, filters and circulators. Ferrite devices are controlled by magnetic fields, and a weak magnetic field is sufficient to control the flow of a powerful microwave signal. Ferrite switches have the advantage over mechanical ones that they have no moving parts subject to wear, and switching is very fast. In Fig. Figure 4 shows a typical ferrite device - a circulator. Acting like a traffic circle, the circulator ensures that the signal travels only along certain paths connecting various components. Circulators and other ferrite switching devices are used when connecting multiple components of a microwave system to the same antenna. In Fig. 4, the circulator does not allow the transmitted signal to pass to the receiver, and the received signal to the transmitter.

The tunnel diode, a relatively new semiconductor device operating at frequencies up to 10 billion hertz, is also used in microwave technology. It is used in oscillators, amplifiers, frequency converters and switches. Its operating power is low, but it is the first semiconductor device capable of operating efficiently at such high frequencies.

Antennas.

Microwave antennas come in a wide variety of unusual shapes. The size of the antenna is approximately proportional to the wavelength of the signal, and therefore designs that would be too bulky at lower frequencies are quite acceptable for the microwave range.

The designs of many antennas take into account those properties of microwave radiation that bring it closer to light. Typical examples include horn antennas, parabolic reflectors, metallic and dielectric lenses. Helical and spiral antennas are also used, often manufactured in the form of printed circuits.

Groups of slot waveguides can be arranged to produce the desired radiation pattern for the radiated energy. Dipoles like the well-known television antennas installed on roofs are also often used. Such antennas often have identical elements located at intervals equal to the wavelength, which increase directivity due to interference.

Microwave antennas are typically designed to be extremely directional because in many microwave systems it is important that energy is transmitted and received in a precisely defined direction. The directivity of the antenna increases with increasing its diameter. But you can make the antenna smaller while maintaining its directivity if you move to higher operating frequencies.

Many "mirror" antennas with a parabolic or spherical metal reflector are designed specifically to receive extremely weak signals coming, for example, from interplanetary spacecraft or from distant galaxies. In Arecibo (Puerto Rico) there is one of the largest radio telescopes with a metal reflector in the form of a spherical segment, the diameter of which is 300 m. The antenna has a fixed (“meridian”) base; its receiving radio beam moves across the sky due to the rotation of the Earth. The largest (76 m) fully movable antenna is located in Jodrell Bank (UK).

New in the field of antennas - an antenna with electronic directivity control; such an antenna does not need to be mechanically rotated. It consists of numerous elements - vibrators, which can be electronically connected to each other in different ways and thereby ensure the sensitivity of the “antenna array” in any desired direction.

20 November 2007
.WITH. Sapunov

Microwave or, otherwise, ultra-high frequency (microwave) radiation is electromagnetic waves with a length of one millimeter to one meter. The scope of application of microwave technology is currently quite wide and, as science and technology develop, it is increasingly being introduced into our daily lives. In addition to the microwave ovens under consideration, such areas of application as radar, radio navigation, satellite television systems, cellular telephone communications and much more can be noted. Recently, intensive and unsuccessful research has been carried out on the use of microwaves in medicine and biology.

The physical nature of microwave radiation is the same as that of light or radio waves. The difference is only in the frequency with which electromagnetic oscillations occur, or in the wavelength, which is the same, since the latter is related to frequency by the relation:

λ=c/f, where

λ - wavelength,
c is the speed of wave propagation;
f - frequency.

The frequency with which the electromagnetic field oscillates greatly affects its external properties. Everyone knows about the existence of radio waves, infrared or thermal and ultraviolet radiation, x-rays and visible light. But all these are different manifestations of the same phenomenon - electromagnetic waves.

The difference lies in only one thing - the oscillation frequency (Fig. 1).

Rice. 1 Electromagnetic wave scale

And, nevertheless, the properties of the listed phenomena may differ like day from night. The reason lies in the commensurability of the wavelength with various physical objects. For example, light or X-ray radiation easily passes through a crystal in which the distance between atoms is less than the wavelength and, conversely, long-wave radiation cannot penetrate, say, a metal pipe of even a very large diameter.

Therefore, if you somehow mysteriously find yourself in an all-metal tunnel with a transistor receiver, do not try to shake it or hit it against the wall in the hope of extracting sounds other than crackling and hissing.

If in low-frequency electronics it is customary to operate in terms of currents and voltages, then in the microwave range in most cases quantities characterizing the electromagnetic field are used. The main ones are the electric field strength E and the magnetic field strength H.

For clarity, electric and magnetic fields are usually depicted as lines of force. Lines of force are not really existing physical quantities, but only help to graphically display something that has no shape, no color, no smell. The tangent to the field line indicates the direction of the force acting on the electric charge or magnetic dipole, and the density of the field lines indicates the magnitude of the field strength.

For example, in Fig. Figure 2 shows the magnetic field around a current-carrying conductor and the electric field formed by two point charges.

Rice. 2. Electric field lines E formed by two opposite point charges and magnetic field lines around a conductor with current H

The wavelength of the microwave field is of the same order of magnitude as the components of electrical circuits, so the latter greatly influence its distribution. If a resistor is included in the microwave circuit, then its orientation in space, the dimensions and length of the leads are of the same importance as the nominal value, and in some cases even more important. Components such as capacitors and inductors are generally made on microwave boards in the form of thickening or narrowing of the current-carrying conductor. This has some advantage, since many passive elements can be technologically implemented very easily and at minimal cost.

For example, the oscillatory system of a magnetron used in microwave ovens is a stamped copper blank with special holes. A similar design at lower frequencies would require dozens of capacitors and inductors. But for everything in life you have to pay. In this case, some simplicity in manufacturing is more than offset by complexity at the stage of calculation and design. This is one of the reasons that hinders the widespread adoption of microwave technology. There are others, no less important.

It is more difficult to carry out measurements at ultrahigh frequencies. For example, characteristic impedance, although measured in ohms, cannot be measured with an ohmmeter.

The electrical parameters of microwave technology elements are distributed in nature. If in a radio engineering oscillatory circuit the electrical energy is concentrated in the capacitor, and the magnetic energy in the inductor, then in the microwave resonator, which performs the same function, the electric and magnetic fields are intertwined and it is not possible to separate the capacitance from the inductance, except in certain specific cases. A pie heated in a microwave oven and, accordingly, being a load on the microwave circuit, introduces additional capacitance into it, as well as inductance and resistance. By moving the patty inside the chamber, we change the relationship between these parameters, so it makes no sense to measure the patties in microfarads, even if they were well suited for use in microwave circuits for other reasons.

Another obstacle to microwave technology lies in the plane of theory. In classical electrical engineering, there are a number of fundamental laws, such as Ohm's law, Kirchhoff's laws, etc., with the help of which you can calculate an electrical circuit. Sometimes it is simple, sometimes it is very simple, and sometimes it is extremely difficult, but nevertheless it is possible.

However, in the microwave range, the application of these laws in their pure form is, as a rule, impossible. How, for example, can we use Ohm’s law, which establishes the relationship between current and voltage, if the concept of voltage itself is missing? All laws of classical electrical engineering are limited. This does not mean at all that they are incorrect, but they are valid only where there is no radiation.

It was previously noted that radio waves and visible light have the same physical nature. But no one would think of measuring the brightness of sunlight in volts or amperes. In turn, the laws of optics are difficult to use when designing an electric kettle. There is nothing unusual in the limited application of physical laws. In nature, such phenomena occur at every step. For example, in mechanics it was once discovered that at speeds close to the speed of light, Newton’s laws, which for a long time were considered immutable, are not fulfilled. And only after the advent of Einstein’s theory of relativity, which complemented Newton’s mechanics, everything fell into place. It turned out that there is a more general law of nature, which includes Newton's law as an integral part.

A similar situation has developed in electrodynamics. There are Maxwell's equations that more fully describe the processes associated with the electromagnetic field in the entire spectrum of electromagnetic oscillations. The laws of classical electrical engineering, like the laws of optics, can be considered special cases of Maxwell's equations.

In turn, Maxwell's equations are not universal. During electromagnetic interactions of elementary particles, the laws of quantum mechanics come into force, supplementing Maxwell's equations. It is quite possible that after some time the laws of quantum mechanics will also have to be considered as a special case of a more general theory.

For a long time, scientists have been trying to develop a unified field theory that unites all known types of interactions: gravitational (describing the forces of attraction), electromagnetic, strong and weak (the latter manifest themselves at the level of the atomic nucleus). A reasonable question may arise: why use a large number of specific laws at all? Isn’t it easier to use one universal one?

But the problem is that the more general a particular law of nature is, the more difficult its practical use. For example, the most inveterate C student, having the necessary formulas at hand, can easily calculate the power lost in a resistor during the passage of electric current. But try solving the same problem using Maxwell's equations. Without any stretch of the imagination, this is a subject for a doctoral dissertation. For illustration purposes only, the system of these equations for an isotropic and homogeneous medium is given below:

What will happen in the case of an anisotropic and inhomogeneous medium, the reader can guess for himself. If electrical engineers had to use exclusively these equations in their work, we would most likely still be reading by candlelight.

Fortunately, nature decreed otherwise. Thus, in low-frequency electronics, much simpler physical laws are used that can be theoretically derived from Maxwell's equations, although to be fair, it should be noted that most of them were experimentally discovered before Maxwell created his equations. This simplification is possible when the dimensions of the electronic components are much smaller than the wavelength. In this case, there is practically no radiation of radio waves and, therefore, we can assume that all the energy is transmitted along the conductors in the form of electric current.

Note.

In fact, in this case too, energy is transmitted through an electromagnetic field. The wires only indicate the route to the field. As proof, a simple example can be given: regular telephone communication between St. Petersburg and Vladivostok is carried out by wire. If energy were transmitted not by a field, but by current carriers - electrons, the speed of which is significantly less than the speed of light, then the answer to “Hello!” I would have to wait for hours.

As an example, imagine that there is a resistor in the path of a conductor carrying current. If there is no radiation, the power lost in it can be easily calculated using a simple formula:

But, if the same resistor is placed in the path of propagation of an electromagnetic wave, then the result will not be so obvious.

As already noted, the microwave range is that part of the electromagnetic spectrum where classical electrical engineering no longer works, and the relatively simple laws of optics do not yet work. Therefore, when solving electrodynamic problems in the specified range, one has to either become more sophisticated, adapting the laws of optics and classical electrical engineering to microwave frequencies, or try to solve Maxwell’s equations, which in some cases bears fruit.

The meaning of these equations is as follows:

First equation tells us that the source of the magnetic field can be either a flowing current or an electric field varying over time. In some ways, these are similar things, since electric current is the movement of electric charges, and each moving charge changes the surrounding electric field and thereby creates a magnetic field around itself.

This explains the existence of a magnetic field around DC conductors. It is created by the totality of all charges moving along a conductor.

From the second equation it follows that a time-varying magnetic field generates a closed electric field. Let us dwell on this consequence in more detail.

In low-frequency electronics, it is generally accepted that the source of the electric field is electric charges. In this case, the field lines emanate from the surface of the charge or converge on it. Maxwell's system of equations does not reject this; this property is reflected in the third equation; however, in addition to this, there can be such a configuration of the electric field when its field lines are closed on themselves, similar to magnetic field lines.

Such a field can only exist in dynamics, and the faster the magnetic field changes, the more favorable the conditions for the emergence of an electric one. That is why at low frequencies field effects practically do not appear and can be neglected. The presence of a ring electric field creates the possibility for the emergence and propagation of radio waves.

Let me explain this with the following example: let’s say we have a conductor through which a high-frequency current flows. There will therefore be a rapidly changing magnetic field around this conductor. This, in turn, will lead to the appearance of an annular electric field varying with the same frequency. The latter will generate a magnetic field, and so on ad infinitum. The original conductor with current, which is the antenna, only initiates the process, and then everything happens by itself. The energy of the electric field transforms into magnetic energy, and vice versa. Moreover, this whole process does not stand still, but spreads at the maximum permissible speed - 300,000 km/sec.

And finally Maxwell's last equation indicates the absence of single magnetic charges in nature. The latter circumstance introduces some asymmetry into the system of equations.

Indeed, if in electrostatics there are positive and negative charges that can exist independently of each other, then the magnetic poles are inseparable, like Siamese twins. No matter how small we crush a permanent magnet into, we will never get a separate S or N pole. Such an asymmetry, as if demonstrating the priority of one field over another, has confused many physicists since the appearance of the equations in question. Attempts to discover a separate magnetic pole have never stopped and are still being undertaken. And not just out of idle scientific curiosity. If it were possible to separate the magnetic poles in practice, it would make such a revolution in technology, the scale of which is difficult to even imagine.

Finishing with the analysis of Maxwell's equations, let's take a short excursion into history. In the middle of the last century, when these equations were obtained, no one had yet suspected the existence of electromagnetic waves. These equations seemed to generalize and bring together everything that was known to physicists of that time about electricity and magnetism. Only as a result of analyzing the resulting equations did Maxwell come to the conclusion about the presence of electromagnetic waves in nature and the speed of their propagation, which exactly coincided with the speed of light known at that time.

Based on this, a hypothesis was put forward about the electromagnetic nature of visible light, confirmed by further research.

Approximately the same situation arose when Mendeleev discovered his Periodic Table, which predicted the existence in nature of many chemical elements hitherto unknown to science. In this regard, it is appropriate to quote the words of the German physicist Heinrich Hertz, dedicated to Maxwell’s theory: “It is impossible to study this amazing theory without at times experiencing the feeling that mathematical formulas live their own life, have their own mind - it seems that these formulas are smarter than us, smarter even the author himself, as if they give us more than was originally included in them.”

And indeed, could Maxwell have imagined what a revolution in people’s lives would be made by the practical implementation of inventions based on his four equations.

Good luck with the renovation!

All the best, writeto © 2007

Microwave radiation is a type of non-ionizing radiation characterized by a frequency of electromagnetic oscillations from 3×10 8 to 3×10 11 Hz and a wavelength from 1 meter to 1 millimeter.

Classification of microwave waves

An electromagnetic field (EMF) is formed around any source of electromagnetic radiation, which consists of alternating electric and magnetic fields.

There are 2 zones of this field:

1stzone - unformed wave zone (near zone, or induction field, or standing wave field);

2nd zone - formed wave zone (far zone, or radiation field, or traveling wave field).

The zone of the formed wave is of greatest interest, since the near zone is limited to only a distance of two wavelengths . The intensity of EMR in this zone is estimated by the amount of energy incident per unit surface, i.e., by the energy flux density (EFD). The unit of measurement for PES is W/cm2, in medicine – mW/cm2 (milliwatt per square centimeter).

The EMR penetration depth is the distance at which the wave intensity decreases by 2.7 times.

The size of the wave determines its penetrating ability, which is approximately 1/10 of the length; therefore, decimeter waves are capable of penetrating to a depth of 10–15 centimeters and most of the internal organs of a person are in the zone of their influence. In general, we can say that The depth of penetration of EMR into tissues is smaller, the shorter the wavelength, and energy absorption by tissues, on the contrary, increases with decreasing wavelength. Of the total amount of EMR energy falling on a human surface, approximately 50% is absorbed, the rest is reflected.

Biological effect of electromagnetic radiation in the microwave range on the human body.

The mechanism of the biological action of microwave EMR is characterized by significant complexity, since the physical nature of the primary processes of interaction with biomolecules and the subsequent links of the resulting changes have not been fully elucidated.

Unlike ionizing radiation, which directly creates electrical charges, EMR does not have ionizing ability and only affects existing free charges or dipoles. There are a number of hypotheses, most of which are based on the principles presented in the biophysics course. From the theory of the electromagnetic field it is known that if a charge moving under the influence of a magnetic field is simultaneously affected by an electric field directed along the movement of the charge, then a significant acceleration of charged particles is achieved. One can imagine that similar processes occur in a living system when an organism is exposed to an electromagnetic field.

The second position is that when exposed to an electromagnetic field on the human body, the conductivity and dielectric constant of tissues change, which increases the amount of absorbed energy, especially in tissues with a high water content.

Currently, it is customary to distinguish between the so-called thermal effect (heating of irradiated tissues) at an energy flow exceeding 10 – 15 mW/cm 2 And athermic effect when the irradiation intensity is below the threshold of thermal action (PE value >10 mW/cm 2 ).

The thermal effect is caused by an increase in the kinetic energy of biomolecules, which is introduced by an external electromagnetic field. Molecular dipoles, especially water dipoles, change the speed and direction of their movement, receive a certain acceleration; due to inertia, some of the molecular dipoles do not have time to orient themselves in the direction of the rapidly changing field, which causes the moving dipoles to collide with each other and, ultimately, leads to an increase in temperature.

When absorbing EMR from the microwave range, in addition to integral heating, loci of more intense energy absorption (“hot spots”) appear in them due to the chemical heterogeneity and structural features of tissues. If they are located in or near vital regulatory centers, irreversible changes are possible.

The resulting heat can lead to heating, overheating and even burns in certain areas of the body. Naturally, tissues with a high water content heat up more and this process occurs faster; blood circulation for the time being reduces the temperature of the tissues, especially those where it is carried out intensively. Where blood circulation is slowed down or exchange occurs by diffusion, heating occurs quickly, and metabolic processes in tissues are significantly accelerated.

It is obvious that such a change in metabolic processes, especially in those organs and tissues where the usual optimal metabolic process occurs at low temperatures, can lead to pronounced pathological changes. The following is installed microwave EMR sensitivity scale : lens, glassy body, liver, intestines, testes.

The nature of the athermic (specific) effect of microwaves on the tissue of living organisms could not be completely deciphered.

A number of theories have been proposed to explain the specific effect of microwave EMF:

1. The theory of “spot” heating - some microstructures, for example, lipid membranes of cells, can heat up much faster than those located nearby.

2. The theory of “pearl chains” - the alignment in chains and orientation along the electromagnetic field lines of solid particles or liquid droplets suspended in another liquid due to the induction of charges in these particles.

3. The theory of non-thermal protein denaturation - breaks in protein chains and carbohydrate bonds due to the transition of molecules to an excited state.

4. The theory of resonant energy absorption by proteins in accordance with the frequency of microwave EMF, which affects the function of organelles, enzymes, etc.

5. The theory of changes in the excitability of receptors, the content of biologically active substances, hormones and vitamins, changes in the processes of synaptic transmission of impulses.

In the mechanism of the specific action of microwave EMF on a living organism, an important role is played by:

1. Changes in the potassium-sodium gradient of the cell due to the different effects of microwaves on the degree of hydration of sodium and potassium ions, as well as on the efficiency of Na-K-nacoca.

2. Change permeability of cell membranes.

3. Disorders of neuroreflex and humoral regulation of the functions of internal organs.

4. Disturbances in the information and management activities of the body due to the interaction of EMF with the electric and magnetic fields of biocurrents and the adjustment of the frequency of the biocurrent generator to the frequency of external EMF (the “dragging” phenomenon).

5. Changes in vibrations of water molecules (dipoles) under the influence of EMR with disruption of metabolic processes in the cell occurring in the aquatic environment.

Both during thermal and athermic effects, an increase in the peroxidation of low-density lipoproteins in human blood serum was noted. High-density lipoproteins reduce the level of lipid peroxidation, which can be used for scientifically based prevention of EMR lesions.

The nature and intensity of irradiation, its duration, the area of ​​the irradiated body surface, wavelength, individual characteristics of a living system, in particular constitutional parameters, type of nervous system, age, heredity, bad habits, state of immunity, biological rhythm are of decisive importance when exposed to EMR in the ultra-high frequency range. , the presence in the range of resonant frequencies for various parts of the body (neck, head, lower and upper limbs).

Pathogenesis of radio wave disease.

In the general pathogenesis of microwave EMR lesions, three stages are distinguished (according to E.V. Gembitsky):

1 – functional (functional-morphological) changes in cells, primarily in the cells of the central nervous system, developing as a result of direct exposure to EMR;

2 – change in reflex-humoral regulation of the functions of internal organs and metabolism;

3 – predominantly indirect, secondary change in the functions (organic changes are also possible) of internal organs.

Stages of formation of microwave EMR lesions.

Adaptive reactions of the body when exposed to microwave EMF are conventionally divided into specific And nonspecific. Adaptive specific reactions are aimed at combating overheating. This is vasodilation, tachycardia, tachypnea, increased sweating, etc.

Nonspecific adaptive reactions are associated with the reflex response of the central nervous system and endocrine glands. At the beginning of exposure to the microwave field or under the influence of low intensities, stimulation of the reflex activity of the central nervous system, endocrine glands and metabolism occurs, and with further exposure, their inhibition occurs. Pathological reactions manifest themselves in the form of foci of hemorrhage, cataracts, degenerative changes in the testes, stomach ulcers, neuroses, neurocirculatory asthenia, hyperthermia, etc.

Classification of lesions caused by ultra-high-frequency electromagnetic radiation.

I. Formation period radio wave sickness.

1. Acute lesions:

a) I degree (mild);

b) II degree (moderate);

c) III degree (severe).

2. Chronic lesions:

a) initial (initial) manifestations;

b) I degree (mild);

c) II degree (moderate);

d) III degree (severe).

II. Recovery period.

III. Consequences and outcomes of ultrahigh-frequency EMR lesions.

Pathogenesis of the influence of microwave fields on the human body.

Clinic of acute and chronic injuries from ultra-high-frequency electromagnetic radiation.

Acute lesions are relatively rare, most often in emergency situations when irradiation with high thermal intensity microwaves occurs. Therefore, the first clinical manifestations are symptoms of overheating of the body and damage to the nervous system, especially when the head area is irradiated. Distinguish 3 degrees of severity of acute EMR lesions : I (light), II (moderate) and III (heavy).

For lesions I (mild) severity Thermal regulation disorders come to the fore, accompanied by heat fatigue, asthenic reactions, headache, autonomic disorders with short-term fainting, severe bradycardia or tachycardia. The blood reaction is limited to slight leukocytosis.

For defeats II (moderate) degree of severity Characterized by more pronounced disturbances in thermoregulation, leading to changes in sweating, oxidative processes and shifts in water-electrolyte balance. Clinically, this is manifested by hyperthermia (total body temperature rises to 39 - 40°), disorders of the central nervous system in the form of motor agitation, inhibited consciousness, sometimes hallucinations and delusional states. There is a tendency towards instability of blood pressure, cardiac arrhythmias are possible (paroxysmal tachycardia, frequent polytopic extrasystoles, impaired atrioventricular conduction), nosebleeds and burns of exposed parts of the body (erythematous dermatitis) may occur. Some time after the lesion, cataracts are detected. When examining peripheral blood, in addition to pronounced leukocytosis, signs of blood thickening and hypercoagulation are revealed.

In case of defeat III (severe) degree there is a rapid development of the process with a predominance of cerebral phenomena, manifested by confusion and loss of consciousness and the occurrence of hypothalamic disorders with angiospastic manifestations (diencephalic crisis). Those affected note fever throughout the body, their health quickly deteriorates, a sharp headache appears, sometimes dizziness and decreased visual acuity, nausea, and less often vomiting. Severe arterial hypertension is determined. Treatment of such lesions always requires a whole range of emergency intensive care measures.

Those who have suffered an acute injury may subsequently experience instability of blood pressure, phenomena of prolonged asthenia and desynchronosis (mood instability, sharply reduced performance, muscle weakness, tremors of the limbs, insomnia or drowsiness, sleep distortion, aching pain in the arms and legs). With damage from millimeter and centimeter waves, burns of open parts of the body and damage to the eyes (cataracts, the development of so-called “dry desquamative” conjunctivitis) are possible.

Chronic lesions EMRs are much more common than acute ones and arise as a result of prolonged repeated exposure to doses exceeding the maximum permissible levels. Chronic lesions of microwave EMR do not have clearly defined (specific) signs and can manifest themselves as functional disorders, primarily of the nervous, cardiovascular and endocrine systems as a result of changes in the reflex-humoral regulation of internal organs and metabolism. In advanced stages of the disease, organic changes in internal organs are also possible. In some cases, local changes occur, mainly in the skin and its appendages, and in the organ of vision (damage to the lens of the eye, the occurrence of chronic conjunctivitis).

Chronic exposure to EMR is divided into: initial (initial) manifestations and lesions of three degrees of severity : I (mild), II (moderate) and III (severe). For initial manifestations lesions, the basis of the clinical picture is asthenic (asthenoneurotic) syndrome; at mild lesions Asthenovegetative (vegetative) syndrome debuts, and with lesions of moderate severity, angioedema and diencephalic syndrome (hypothalamic) occur. At severe lesions to they are accompanied by symptoms indicating a violation of other organs and systems.

First signs asthenic (asthenoneurotic) syndrome As a rule, they appear after 2–3 years of constant (continuous) operation under conditions of exposure to microwave EMR. Patients complain of frequent dull headaches that occur at the end of the working day, general weakness, fatigue, irritability, a feeling of weakness, drowsiness during the day and insomnia at night (desynchronosis), weakening of memory, inability to concentrate and engage in creative mental work, sexual disorders gradually appear. of various types, transient paresthesia and pain in the distal extremities are observed. In general, signs of the predominance of inhibitory processes in the central nervous system, and occasionally autonomic disorders, are objectively revealed.

There may be an increase in the excitability thresholds of the olfactory and visual analyzers and the sensitivity threshold in the distal parts of the extremities, an increase in neuromuscular excitability, an increase in the time of sensorimotor reactions, a deterioration in light and dark adaptation, stability of clear vision, and the distinctive sensitivity of the eyes. Temporary removal from work under the influence of microwave EMR generators and adequate treatment at this stage of the disease lead, as a rule, to the complete disappearance of the above disorders.

Persistent asthenovegetative syndrome most often occurs in individuals exposed to relatively high intensities (up to several mW/cm2). Autonomic disorders are manifested by hyperhidrosis, decreased tactile sensitivity and skin temperature of the hands, pallor of the skin, cyanosis of the distal extremities, muscle hypotension, persistent red diffuse dermographism, changes in galvanic skin reflexes, weakened skin-vascular and cardiovascular reflexes, sluggish vascular reaction to intradermal administration of histamine, asymmetry of vascular tone, changes in positional reflexes - ortho- and clinostatic.

Autonomic dysfunctions most noticeably affect the reactions of the cardiovascular system. Characterized by a predominance of vagal tone, a combination of arterial hypotension with a tendency to bradycardia, and pronounced vagotonic reactions during the Aschner test. The ECG records sinus arrhythmia and bradycardia, atrial and ventricular extrasystoles, and moderate atrioventricular conduction disturbance. Autonomic disorders create certain conditions for the formation of dystrophic changes in the myocardium, which are initially compensated and are detected only after physical activity and during pharmacological tests. In some cases, signs of myocardial dystrophy progress (an increase in heart size, a dull first sound, and a pendulum-like rhythm are detected).

A lesion of moderate severity is characterized by the presence diencephalic syndrome. With a further increase in vascular-vegetative disorders, angiospastic reactions appear and become predominant, blood pressure rises, and spasm of the fundus vessels and skin capillaries is detected. Changes in the myocardium become more constant and pronounced, signs of impaired coronary circulation appear with compressive pain in the heart area. If the phenomena of hypotension and bradycardia can be characterized as neurocirculatory dystonia of the hypotonic type, then the presence of angiospastic reactions with pain in the heart and increased blood pressure can be defined as a manifestation of diencephalic disorders that periodically reach the level of vascular crises. The latter appear suddenly or after a short prodromal period and are manifested by a sudden onset of headache, sometimes with fainting or short-term impairment of consciousness. Soon, pains in the area of ​​the heart of a compressive nature appear, accompanied by severe weakness, sweating, and a feeling of fear. During an attack, the skin becomes pale, chills, and blood pressure rises to very significant figures (180/110 - 210/130 mm Hg). With frequently recurring crises, there may be a sharp drop in blood pressure with the occurrence of collapse.

In patients with periodically manifested diencephalic syndrome, electroencephalography data indicate diffuse changes in the bioelectrical activity of the brain with phenomena of irritation of the limbic-reticular complex. According to most researchers, as work experience increases under conditions of exposure to microwave EMR, peripheral vascular resistance increases, there is a tendency to increase blood pressure, especially diastolic pressure, and the systolic and cardiac output decreases.

Against this background, neurocirculatory dystonia of the hypertensive type subsequently transforms into arterial hypertension, and coronary heart disease of a high functional class develops. All of these conditions can develop many years after you stop using EMR generators.

With moderate severity of chronic lesions against the background of the listed syndromes, endocrine disorders: activation of thyroid function with an increase in its mass (sometimes with clinical signs of thyrotoxicosis I - II degrees), sexual function disorders (impotence, menstrual irregularities). This is also facilitated by the occurrence of chronic gastritis, usually atrophic with intestinal dysplasia of the gastric mucosa; signs of damage to other organs and systems gradually appear. Possible trophic disorders - brittle nails, hair loss, weight loss.

With both mild and moderate severity of chronic lesions, blood counts are unstable. Moderate leukocytosis with a tendency to neutropenia and lymphocytosis is more often noted, sometimes structural changes in neutrophils (pathological granularity, vacuolization of the cytoplasm, fragmentation and hypersegmentation of nuclei), reticulocytosis, decreased acid resistance of erythrocytes, and slight spherocytosis are often detected. With severe forms of damage, there may be a tendency to leukopenia with lymphopenia and monocytosis, thrombocytopenia, signs of delayed maturation of granulocytes and erythroid cells in the bone marrow. Some biochemical parameters may be changed - a slight decrease in cholinesterase activity, impaired release of catecholamines, hypoproteinemia, increased histamine levels, a slight decrease in glucose tolerance.

With various types of exposure to microwave EMR with a wavelength from 1 mm to 10 cm, clouding of the lens (cataract) develops. It can occur both after a single intense irradiation and during chronic exposure to EMR of non-thermal intensity, especially with direct exposure of the radiation to the eyes (more often it occurs in technicians who are directly involved in the repair and adjustment of equipment for microwave EMR generators). Pulsed radiation has the greatest damaging effect.

At severe severity the picture of electromagnetic disorders is progressing. The complaints of patients worsen, and phenomena of obsessive fears and viscosity of thinking arise. Organic brain lesions are often diagnosed, manifested by dysfunction of the cranial nerves, symptoms of oral automatism, increased tendon reflexes, and parasthesias. Hemodynamic disturbances become pronounced in the form of often recurrent and difficult to stop diencephalic crises. The condition is aggravated by the addition of coronary heart disease and duodenal ulcer. An imbalance in the endocrine system is revealed (sexual function is inhibited, thyroid function is disrupted). Indicators of cellular and humoral immunity decrease, autoimmune processes increase. However, at present, a severe degree of chronic EMR damage does not occur due to adequate sanitary and hygienic requirements, proper medical control and clinical observation.

Diagnosis of acute and chronic lesions by microwave field

Diagnosis of acute microwave EMR lesions, as a rule, does not present any great difficulties

Diagnosis of acute EMR lesions

Algorithm for diagnosing chronic microwave EMR lesions

Characteristicworking conditions for those working with microwave EMR

Examples of diagnosis statements:

– acute damage to microwave EMR of moderate severity. Acute moderate overheating of the body (hyperthermic form). Acute psychomotor agitation. An attack of paroxysmal tachycardia (gastric form). Nose bleed;

– chronic damage to microwave EMR of the second degree of severity. Neurocirculatory dystonia of the hypertensive type (protracted course). Chronic gastritis with decreased acid-forming function, atrophic;

– chronic damage to microwave EMR of the second degree of severity. Protracted astheno-vegetative syndrome. Dry desquamative conjunctivitis, fading exacerbation.

Prevention of acute and chronic injuries from ultra-high-frequency electromagnetic radiation.

Prevention of the adverse effects of EMR on persons working with microwave sources is a set of technical, sanitary, hygienic and medical measures defined in the Republic of Belarus by Sanitary rules and regulations 2.2.4/2.1.8.9-36-2002 “Electromagnetic radiation of the radio frequency range (EMR RF)"

A set of measures to prevent microwave EMR injuries

Technical preventive measures include:

Placement of PJIC, radio systems (RTS) at safe distances from barracks, office and residential buildings, establishment sanitary-protection zone and restricted zone. The intensity of EMIPJIC, RTS in the territory of populated areas located in the near zone of the radiation diagram should not exceed 10 µW/cm 2 and in the territory of populated areas located in the far zone of the radiation diagram - 100 µW/cm 2.

Shielding of all elements capable of emitting EMR, shielding of workplaces, grounding of shields.

Special metallized clothing and safety glasses for PES above 1.0 mW/cm 2 .

When working inside shielded rooms, the walls, floors and ceilings of these rooms must be shielded with radio-absorbing materials.

Methods of protection are determined individually in each specific case (during certification of workplaces).

Sanitary and hygienic preventive measures include:

Control of exposure levels in workplaces and surrounding areas. Data from periodic measurements are entered into the facility’s sanitary passport and are used in the certification of workplaces, monitoring working conditions and the health of workers, and in developing safety and/prevention measures.

Health education, training of personnel servicing microwave generators in safety rules.

Establishment of benefits (additional leave and reduction of working hours).

4 Regulation of the time of contact with the EMR source and reducing the duration of work in the irradiation zone if it is impossible to reduce the EMR PES to the maximum permissible levels.

Currently, in the Republic of Belarus, permissible levels of continuous exposure to microwaves for those working with emitting equipment are calculated in accordance with the adopted document “Sanitary rules and regulations 2.2.4/2.1.8.9-36-2002 “Electromagnetic radiation of the radio frequency range (RF EMR)”.

The maximum permissible value of energy exposure (EE PD) for a work shift should not exceed 200 (μW/cm 2) x h. Next, the maximum permissible energy flux density (PE PD) is calculated using the formula:

PPE pdu =EE pd /T,

where T is the duration of the work shift in hours.

Maximum permissible levels of microwave energy flux density depending on the duration of exposure
Duration of exposure, T, h	PPE Remote control , µW/cm 2
8.0 or more
0.2 or less

Principles of treatment of lesions caused by ultra-high-frequency electromagnetic radiation.

A pathogenetically substantiated treatment regimen for microwave field lesions does not yet exist. Treatment is carried out symptomatically in compliance with the principle of individualization.

Scope of medical care for acute microwave EMF injuries

First aid

1. Remove the victim from the area of ​​effect of the damaging factor.

2. Lay on your back with your legs raised.

3. Carry out external cooling (place in a cool place; apply a cold compress to the head, wipe the body with a wet towel; wipe the skin of the forehead and temporal areas with 70% alcohol (vodka), ammonia; while maintaining consciousness, drink cold water.

4. If breathing or cardiovascular system activity is impaired, perform cardiopulmonary resuscitation.

First aid

1. Continue external cooling.

2. If breathing is impaired, restore airway patency, oxygen therapy.

3. For symptoms of cardiovascular failure, administer cordiamine (1 ml subcutaneously), caffeine-sodium benzoate (1 ml of 2% solution intramuscularly).

4. In case of psychomotor agitation and fear reaction, give 1-2 tablets of phenazepam or diazepam orally.

First aid

1. Supplement local cooling with the following measures:

– apply ice packs to the groin areas, along the body;

– wrap in wet sheets for a short time;

– apply a cold compress to the head, use electric fans (one on each side of the body),

Intravenous administration of cooled solutions: 100 ml of 40% glucose solution with 10 units of insulin, 100 - 200 ml of 0.9% NaCl solution.

Aminazine solution 2.5% - 1 - 2 ml intramuscularly.

Prednisolone 60 – 120 mg intravenously.

For pain, analgin solution 50% 2 - 4 ml is administered intravenously per 10 ml of 0.9% sodium chloride solution.

With the development of convulsive syndrome: 0.5% diazepam solution 2 - 4 ml intravenously.

Condition monitoring cordially-vascular and respiratory systems, correction of their function if necessary.

When caring for patients with hyperthermia, it is necessary to avoid prescribing anticholinergic drugs. Also limit the use of non-steroidal anti-inflammatory drugs.

Qualified help

In qualified assistance only those affected with severity II and III require . Activities aimed at relieving overheating syndrome, arterial hypertension, and pain syndrome are ongoing.

With the development of acute respiratory failure, artificial ventilation and oxygen therapy are performed. The syndrome of acute cardiovascular failure, including cardiac arrhythmia, is eliminated with the help of inotropic drugs, antiarrhythmic drugs, and infusion therapy.

In case of central nervous system damage syndrome, depending on the degree and type of disturbance, sedatives, antipsychotics, tranquilizers, hypnotics, drugs that affect the vascular tone of the central nervous system, and nootropic drugs can be used. Noteworthy is the use of sodium hydroxybutyrate, which has a sedative effect and reduces the sensitivity of the brain to hypoxia.

In the event of nosebleeds, tamponade with a hemostatic sponge and intravenous administration of epsilon-aminocaproic acid, ascorbic acid, and dicinone are performed. It is necessary to apply cold to the nose area.

In case of acute visual impairment (blurred vision, double vision, sudden decrease in vision), anticonvulsants and antispasmodics are indicated - 2.4% aminophylline solution 10 - 20 ml intravenously, papaverine solution 2% - 2 ml, dibazol 1% - 1 ml intramuscularly.

Specialized assistance

As part of the provision of specialized care, it is necessary to continue a set of treatment measures aimed at the final and complete relief of life-threatening conditions (hyperthermia, respiratory failure, cardiovascular failure), early diagnosis of complications and consequences of microwave field injuries, and specialized treatment in full with complete rehabilitation of the injured. In the overall range of measures, dietary nutrition, vitamin therapy, the use of adaptogens, physiotherapeutic and psychotherapeutic treatment become important.

Treatment chronic forms of microwave field damage, nonspecific and requires an integrated approach. It consists of diet, regimen, physical therapy, psychotherapy, and, if necessary, physiotherapy and pharmacotherapy. Psychotherapy methods are of great importance.

Organization and conduct of clinical examination of persons working with sources of ultra-high-frequency electromagnetic radiation. Military medical examination.

Medical examination of persons working with microwave EMR sources is organized in accordance with the requirements of the “Instruction on the procedure for medical support of the Armed Forces of the Republic of Belarus” No. 10 of March 15, 2004.

Military personnel and civilian personnel of the Armed Forces, permanently or temporarily working with sources of electromagnetic fields, are taken for dispensary medical registration at the medical center of the military unit (organization of the Ministry of Defense)

Medical control of persons working with microwave EMR

In-depth medical examinations (UME) are carried out in order to timely identify diseases that impede work with sources of electromagnetic fields, as well as monitor the implementation of therapeutic and health measures and their effectiveness. UMO is carried out by garrison and hospital military medical commissions with the participation of the following medical specialists: therapist, surgeon, neurologist, dermatologist, ophthalmologist, otolaryngologist, dentist (for women - gynecologist).

Organizationconducting ULV of persons who have professional contact with microwave EMR.

Based on the ULV data and comparing them with the results of previous examinations, the military medical commission makes a decision on the degree of fitness of the examined person to work with EMF sources. In cases where the outpatient commission finds it difficult to determine the state of health of the subject, he is sent to a hospital with subsequent examination by a military medical commission.

Military medical examination of persons working with EMF sources or appointed to these positions.

Medical examination of military personnel and civilian personnel of the Armed Forces of the Republic of Belarus, appointed (accepted) to work and working with EMF sources, is carried out by garrison, hospital military military personnel, as well as special military military personnel with the mandatory participation of a doctor of the military unit and a command representative. In this case, the commissions are guided by the relevant columns of the Decree of the Ministry of Defense and the Ministry of Health of the Republic of Belarus No. 61/122 dated

07/21/2008 “On approval of the Instruction on determining the requirements for the health status of citizens when registering for conscription stations, conscription for compulsory military service, service in the reserve, military service of reserve officers, military and special training, entry into military service under a contract, in educational institution "Minsk Suvorov Military School" and military educational institutions, military personnel, citizens in the reserve of the Armed Forces of the Republic of Belarus"

Conducting VVE of persons who have professional contact with microwave EMR.

Contraindications for permission to work with EMF sources are as follows:

– blood diseases;

– organic diseases of the central nervous system;

– endocrine diseases;

– epilepsy;

– pronounced asthenic conditions;

– neuroses;

– persistent vascular hypotension;

– organic lesions of the cardiovascular system in the stage of sub- and decompensation (arterial hypertension, atherosclerosis, coronary heart disease, etc.);

– neurocirculatory asthenia;

– peptic ulcer of the stomach and duodenum with frequent exacerbations;

– chronic hepatitis, pancreatitis;

– pronounced chronic conjunctivitis and ulcerative blepharitis;

– trachoma, complicated diseases of the cornea;

– recurrent keratoconjunctivitis;

– cataract of any etiology;

– aphakia;

– diseases of the optic nerve, retina and choroid;

– advanced glaucoma;

– chronic skin diseases.

LITERATURE:

Main:

Military field therapy: textbook / A.A. Bova [and others]; edited by A.A. Bova. 2nd ed. Minsk: BSMU, 2008. 448 p.

Military field therapy. Workshop: textbook. allowance /A.A. Bova [and others]; edited by A.A. Bova. Minsk: BSMU, 2009. 176 p.

Additional:

Bova, A.A. Combat therapeutic pathology: organization of therapeutic care in modern conditions: textbook / A.A. Bova, S.S. Gorokhov. Minsk: BSMU, 2006. 44 p.

Normative legal acts:

4. On the approval of the Instructions on the procedure for organizing and conducting military medical examinations in the Armed Forces of the Republic of Belarus and the transport troops of the Republic of Belarus and the recognition as invalid of certain resolutions of the Ministry of Defense of the Republic of Belarus: Resolution of the Ministry of Defense of the Republic of Belarus. Belarus dated November 2, 2010, No. 44. Minsk, 2010. 130 p.

5. On approval of the Instruction on determining the requirements for the health status of citizens when registering for conscription stations, conscription for compulsory military service, service in the reserve, military service of reserve officers, military and special training, enrollment in military service under a contract, in the educational institution "Minsk Suvorov Military school" and military educational institutions of military personnel, citizens in the reserve of the Armed Forces of the Republic of Belarus: resolution of the Ministry of Defense and the Ministry of Health of the Republic. Belarus, December 20, 2010, No. 51/170. Minsk, 2011. 170 p.

How exactly does a microwave oven work? What causes food, water and other substances to heat up, while the air or glass in the microwave barely heats up? How to properly handle a microwave oven so as not to damage it and the food you are preparing? You will find answers to these questions in our article!

How does a microwave oven work?

The correct full name of a microwave oven is an oven with ultrahigh frequency currents (microwave). Inside it (behind the dashboard) there is a special device for emitting radio waves - a magnetron, which can be seen from the diagram:

When a magnetron operates, the electromagnetic vibrations it emits at a certain frequency cause the dipole molecules inside the furnace to vibrate at the same frequency. The most common dipole molecule in nature is a water molecule (in foods there are also fats and sugars). At the molecular level, high vibration frequency translates into increased temperature, so any food with a high water content will heat up quickly. If there are very few or no water molecules inside the products (or materials), almost no heating occurs.

The depth of penetration of microwaves is small - 2-3 centimeters, but the surface of the prepared dish is easily penetrated by microwave waves, and deep down they encounter resistance from water molecules, so the product is actually heated from the inside.

Any conductive materials inside the microwave will become hot. Different ability to conduct current in our case means different heating rates.

To ensure that food is heated evenly, several approaches are used:

• Heat-resistant glass disc at the bottom of the microwave oven. It rotates with the dish, exposing all its sides to the magnetron radiation.
• Microwave. They are fed through a special waveguide (wide tube) from the magnetron to a rotating reflector, usually located in the upper part of the microwave oven. In such microwaves you can heat stationary dishes of large size and weight.

There are also so-called inverter microwave ovens. They differ from conventional models in that the magnetron operates continuously, but with reduced power consumption. This is achieved by using a so-called inverter (DC to AC converter) in the furnace instead of a traditional transformer.

In inverter ovens, vitamins are better preserved and the surface structure of the dish is less destroyed, but there is no fundamental difference.

In many microwave oven models, the magnetron is covered with a special translucent plate. It is transparent to microwave rays, but does not allow steam, grease splashes and other foreign substances to enter the microwave through the hole in the shielding. Do not remove this plate, and if it is required for cleaning from grease, then after complete drying, be sure to return it to its place.

Find everything about cleaning a microwave oven in this article:.

Despite popular belief, microwave radiation does not kill germs. At least this has not been scientifically proven. On the other hand, the combined effect of high temperature and microwaves on water molecules inside bacteria and viruses reduces their number many times over within a few minutes, and your immune system copes with those that remain on its own.

Microwave operating frequency

Most magnetrons emit waves at a frequency of 2450 MHz (megahertz, or millions of vibrations per second). These are waves of decimeter length (12.25 cm long). Some industrial installations, for example in the USA, operate at 915 MHz. Forced vibrations of water molecules are not resonant vibrations, since for them the resonant frequency is an order of magnitude higher - 22.24 GHz (gigahertz, or billions of vibrations per second).

There is no need to be afraid of harmful radiation from a microwave. The first mass production of microwave ovens was made in Japan by Sharp in 1962. Many years have passed since then, tens of millions of Japanese have been heating food in microwave ovens for decades, and the average life expectancy of the Japanese is the envy of the whole world.

At a distance of half a meter from a microwave oven, the impact of microwaves weakens 100 times, so if you are afraid of getting radiation, it is enough to stay at arm's length from the microwave.

You can find more information about the effects of microwave ovens on humans. Only scientific facts!

How does a microwave grill work?

A grill allows you to microwave food using regular heat rather than microwaves. It is she who creates an appetizing crust on dishes, which does not appear during conventional microwave processing.

The grill spiral is located at the top of the oven and comes in two types:

• heating elements(thermal electric heaters). A heating element is a metal tube, inside of which there is a thin spiral made of an alloy of nickel and chromium. Current passes through the coil and it heats up.
• Quartz. A quartz grill is also a heating element, but instead of a metal tube there is a glass shell, and between the spiral and the tube there is insulating quartz sand.

Conventional metal heating elements can often be adjusted - moved to the back wall or lowered, but the glass surface of a quartz grill is easier to clean (grease and carbon deposits do not eat into the glass as they do into metal).

There are designs of microwave ovens with grill and convection. Convection is simply blowing hot air over your food as it cooks. For such airflow, a fan is installed in the microwave, blowing heated air from the grill spiral towards the dish.

Most microwave oven models allow you to use both heating elements and microwaves at the same time. However, be aware that this combination can cause a lot of heat in the outlet and wires in your premises.

Read the following article about the principles of choosing a microwave oven to suit your needs:.

Instructions for using a microwave oven

To properly handle your microwave, you need to carefully approach all points - from choosing dishes to properly turning it off after use.

What kind of cookware should I use?

The best material for heating in the microwave is heat-resistant glassware. Porcelain and other ceramic products, paper (cardboard) are also well suited. Microwaves pass through them very easily and hardly heat them up. But you should avoid dishes made from the following materials:

• Plastic. It transmits microwave radiation well, but due to toxic components in manufacturing (for example, polystyrene foam) it can pose a danger to your health.
• Metal. They conduct electricity without allowing microwaves to pass through. So you won’t be able to cook or simply reheat a dish in an aluminum pan or cast iron pot. Metal simply will not allow electromagnetic waves to reach the food, and it will remain cold. In this case, the metal itself will, of course, heat up, and the food can also heat up from its heat. But this can lead to damage to the microwave oven, and you will have to wait a long time for the dish to cook. Read the instructions for repairing microwave ovens.

Some materials may contain metals, and this can be difficult to guess in advance. For example, this is crystal. So it is worth reading carefully on the label what materials were used in the production of a particular cookware.

• Melamine. This is a light and beautiful material for dishes, similar to porcelain, but it cannot be placed in a microwave oven. The fact is that when heated, it releases toxins that are dangerous to your health.

As for the shape of the cookware, it can be any, but not with a narrow neck, since it can be dangerous when used for heating in the microwave. The fact is that some liquids are heated to the boiling point, but violent mixing inside the volume does not occur. But when you take such a jug or flask out of the microwave oven, the liquid will instantly boil, boiling foam will pour out of the container, and you can get burned. For example, distilled water and some purified vegetable oils behave this way under certain conditions.

Correct handling of products

Initially, it is worth determining exactly what cannot be defrosted in the microwave:

• Butter. If you put it in the microwave and leave it for a long time, it will not only melt, but also boil, staining the entire oven from the inside. This happens because inside the oil there is not only the oil itself, but also water. It boils at 100 degrees, and oil at about 120. So the water can turn into steam even before the butter melts, and the water vapor will spread the oil throughout the stove.

About the same thing can happen with other products that sometimes need to be melted, for example, chocolate, so it is better to do this not in the microwave, but by steaming it.

• Products with a dense shell. For example, these are eggs, tomatoes, whole poultry liver. When heated, some of the water not only gradually heats up, but immediately turns into steam. If you heat food for a long time, then even more steam is generated from direct heating. This steam has nowhere to escape, so the pressure inside the container increases and leads to an explosion.
• Hermetically sealed container. For example, canned food and bottles. The reason is the same as in the previous paragraphs - there is a high probability of an explosion.

• Before microwave heating, sausages tightly packed in a casing must be pierced with a fork to create holes for steam to escape, otherwise it will turn the sausages from the inside.
• In eggs and other foods, you need to destroy all the outer and inner shells, for example, make an omelet or cut the liver.
• To cook eggs and other products in the microwave, special saucepans with shielding are used. Water is poured into it, it is heated by microwave waves, but electromagnetic radiation does not reach the eggs - they are covered by a screen.
• If you place a small dish in the microwave, you should add a regular glass of water to it. This way you will avoid overheating of the magnetron.
• It is better to salt any liquid dishes in the microwave in advance, and not after cooking. This way you will save time and energy. The fact is that distilled (unsalted) water heats up and boils in the microwave, but longer than regular water.
• A very frozen product (meat, for example) will take quite a long time to defrost in the microwave, and you need to turn on the microwave oven at minimum power. The reason is that ice molecules are not water molecules, microwave waves do not loosen them so intensely. In addition, ice molecules form a fairly rigid structure and are not as easy to “rock” as water molecules.

Dry bread is often recommended to be “softened” in the microwave, but it can catch fire with prolonged exposure and maximum microwave power. The same can happen even with popcorn designed to be cooked in the microwave. Therefore, you need to be vigilant when placing such foods in the microwave.

On/off rules

You cannot turn on an empty microwave, especially at full power:

1. Inside the oven, all the walls (and even the door) are a special metallized screen that reflects microwaves back into the microwave. The only place where there is no screen is the hole for the exit of electromagnetic waves from the magnetron.
2. When there is food on the tray, the microwaves use their energy to heat the food. If there is nothing to absorb energy, microwave radiation is reflected from the walls of the shielding surfaces, and the wave density increases more and more.
3. Microwave radiation falls back into the magnetron, and if it is made of metal, it will simply overheat and may fail.

It is believed that after heating a dish in a microwave oven, it is better to let it stand for 3-5 minutes. Then the so-called “free radicals”, that is, parts of molecules that have broken apart under the influence of microwaves, have time to be neutralized.

Video: How does a microwave oven work?

All of the above about the principle of operation of the device is well illustrated in the following video:

After reading our article, you began to understand much better the principle of operation of a microwave oven. Now you know what it can do better than a conventional oven and electric stove, and what it cannot do, and what actions are generally unacceptable when working with a microwave.

In contact with

Among the huge variety of electromagnetic waves that exist in nature, microwave or microwave radiation (microwave) occupies a very modest place. This frequency range can be found between radio waves and the infrared part of the spectrum. Its length is not particularly great. These are waves with a length of 30 cm to 1 mm.

Let's talk about its origin, properties and role in the human environment, about how this “silent invisibility” affects the human body.

Microwave radiation sources

There are natural sources of microwave radiation - the Sun and other space objects. It was against the background of their radiation that the formation and development of human civilization took place.

But in our century, saturated with all kinds of technical achievements, man-made sources have also been added to the natural background:

• radar and radio navigation installations;
• satellite television systems;
• cell phones and microwave ovens.

How microwave radiation affects human health

The results of a study of the influence of microwave radiation on humans made it possible to establish that microwave rays do not have an ionizing effect. Ionized molecules are defective particles of matter that lead to mutation of chromosomes. As a result, living cells can acquire new (defective) characteristics. This finding does not mean that microwave radiation is not harmful to humans.

The study of the influence of microwave rays on humans has made it possible to establish the following picture - when they hit the irradiated surface, partial absorption of the incoming energy by human tissue occurs. As a result, high-frequency currents are excited in them, heating the body.

As a reaction of the thermoregulation mechanism, increased blood circulation follows. If the irradiation was local, rapid heat removal from heated areas is possible. With general radiation there is no such possibility, so it is more dangerous.

Since blood circulation acts as a cooling factor, the thermal effect is most pronounced in organs depleted of blood vessels. First of all, in the lens of the eye, causing its clouding and destruction. Unfortunately, these changes are irreversible.

The most significant absorption capacity is found in tissues with a high content of liquid components: blood, lymph, mucous membrane of the stomach, intestines, and the lens of the eye.

As a result, you may experience:

• changes in the blood and thyroid gland;
• decreased efficiency of adaptation and metabolic processes;
• changes in the mental sphere, which can lead to depressive states, and in people with an unstable psyche, provoke suicidal tendencies.

Microwave radiation has a cumulative effect. If at first its effects are asymptomatic, then pathological conditions gradually begin to form. Initially, they manifest themselves in increased headaches, fatigue, sleep disturbances, increased blood pressure, and heart pain.

With prolonged and regular exposure to microwave radiation, it leads to the profound changes listed earlier. That is, it can be argued that microwave radiation has a negative impact on human health. Moreover, age-related sensitivity to microwaves was noted - young organisms turned out to be more susceptible to the influence of microwave EMF (electromagnetic field).

Means of protection against microwave radiation

The nature of the impact of microwave radiation on a person depends on the following factors:

• distance from the radiation source and its intensity;
• duration of irradiation;
• wavelength;
• type of radiation (continuous or pulsed);
• external conditions;
• state of the body.

To quantify the danger, the concept of radiation density and permissible exposure rate was introduced. In our country, this standard is taken with a tenfold “safety margin” and is equal to 10 microwatts per centimeter (10 μW/cm). This means that the power of the microwave energy flow at a human workplace should not exceed 10 μW for each centimeter of surface.

How to be? The obvious conclusion is that exposure to microwave rays should be avoided in every possible way. Reducing exposure to microwave radiation in the home is quite simple: you should limit the time of contact with household sources.

People whose professional activities involve exposure to microwave radio waves should have a completely different protection mechanism. Means of protection against microwave radiation are divided into general and individual.

The flux of emitted energy decreases in inverse proportion to the increase in the square of the distance between the emitter and the irradiated surface. Therefore, the most important collective protective measure is to increase the distance to the radiation source.

Other effective measures to protect against microwave radiation are the following:

Most of them are based on the basic properties of microwave radiation - reflection and absorption by the substance of the irradiated surface. Therefore, protective screens are divided into reflective and absorbent.

Reflective screens are made of sheet metal, metal mesh and metallized fabric. The arsenal of protective screens is quite diverse. These are sheet screens made of homogeneous metal and multilayer packages, including layers of insulating and absorbing materials (shungite, carbon compounds), etc.

The final link in this chain is personal protective equipment against microwave radiation. They include workwear made of metallized fabric (robes and aprons, gloves, capes with hoods and goggles built into them). The glasses are covered with a thin layer of metal that reflects radiation. They are required to be worn when exposed to radiation of 1 µW/cm.

Wearing protective clothing reduces the level of radiation exposure by 100–1000 times.

Benefits of microwave radiation

All previous information with a negative orientation is intended to warn our reader from the danger emanating from microwave radiation. However, among the specific effects of microwave rays, the term stimulation is found, that is, an improvement under their influence in the general condition of the body or the sensitivity of its organs. That is, the effect of microwave radiation on humans can be beneficial. The therapeutic property of microwave radiation is based on its biological effect in physiotherapy.

Radiation emanating from a specialized medical generator penetrates the human body to a given depth, causing tissue heating and a whole system of useful reactions. Microwave treatment sessions have an analgesic and antipruritic effect.

They are successfully used to treat frontal sinusitis and sinusitis, trigeminal neuralgia.

To influence the endocrine organs, respiratory organs, kidneys, and treat gynecological diseases, microwave radiation with greater penetrating power is used.

Research into the effect of microwave radiation on the human body began several decades ago. The accumulated knowledge is sufficient to be confident that the natural background of these radiations is harmless to humans.

Various generators of these frequencies create an additional dose of impact. However, their share is very small, and the protection used is quite reliable. Therefore, phobias about their enormous harm are nothing more than a myth if all operating conditions and protection from industrial and household sources of microwave emitters are met.