MINISTRY OF EDUCATION OF UKRAINE
NATIONAL TECHNICAL UNIVERSITY OF UKRAINE (KPI)
Faculty of Military Training
Essay
by discipline
“Fundamentals of construction and design of air defense systems”
“The concept of microwave radio waves.
Features of their distribution"
Introduction
The concept of radar includes the process of detecting and determining the location of various objects in space using the phenomenon of reflection of radio waves from these objects.
In this regard, the characteristics of the radio waves used and the characteristics of their propagation in various conditions are of paramount importance to achieve the required result.
Electromagnetic oscillations of ultra-high frequency (microwave oscillations) are of particular interest to us, since the corresponding VHF range has certain advantages compared to waves of other ranges.
1. The concept of microwave radio waves
Radar uses ultra-high frequency electromagnetic oscillations, which correspond to the VHF band. The following table shows the accepted division of the VHF band:
The use of VHF bands is explained by the advantages inherent in radio waves of this range compared to waves of other ranges.
VHF radio waves are well reflected from objects encountered along the path of their propagation. This allows you to receive intense signals reflected from targets irradiated by the radar station. In the VHF range it is easier to obtain a highly directional radio beam necessary for measuring the angular coordinates of a target. In this range there is significantly less industrial interference.
The first radar stations operated in the meter range; they had low resolution and low accuracy in determining the angular coordinates of targets. Currently, almost the entire centimeter wavelength range is practically used in radar and the millimeter wavelength range is beginning to be mastered. In these ranges, radar stations have relatively small-sized antennas that are highly directional and have high resolution, which is necessary to increase the accuracy of determining the angular coordinates of objects.
2. Features of the propagation of microwave radio waves
By analogy with light waves, VHF propagate in a straight line and bend only around objects that have geometric dimensions commensurate with the wavelength. When radio waves bend around obstacles, diffraction affects them the more strongly, the longer the wavelength and the smaller the size of the obstacle. At the boundary of two media, radio waves are reflected according to the law of optics - the angle of incidence is equal to the angle of reflection. Partial refraction of radio waves also occurs according to the laws of optics. Large artificial structures and mountains in the path of radio waves, as well as the spherical shape of the earth, prevent the propagation of radio waves along the earth. The range of a detection radar is usually limited by the line of sight between its antenna and the target. Line of sight range (geometric) can be determined by the formula:
Where h – height of the radar antenna above the ground in meters,
H – target height above the ground in meters.
This formula is easily derived from simple geometric relationships, taking into account the radius of the globe, equal to 6400 km. The range of a detection radar is influenced by many factors. The propagation of microwave waves in the lower layers of the atmosphere depends on humidity, temperature and atmospheric pressure. The upper layers of the atmosphere, where gas ionization (splitting of electrically neutral atoms) occurs under the influence of the sun and cosmic rays, affects the propagation of only the longest waves in the VHF range. When radio waves propagate in denser layers of the atmosphere, the effect of refraction of radio waves appears due to the heterogeneity of the layers of the atmosphere. The smooth deviation of a beam from the straight path of its propagation is called refraction. Radio waves, penetrating into denser layers, reduce their speed and, conversely, leaving dense layers, increase it. As a result, the radio beam deviates from a straight section either with a convex upward, bending around the earth, or with a convex downward, moving away from the earth's surface. The range of the radar either increases or decreases accordingly.
Of particular interest is the phenomenon of critical refraction or superrefraction, when the curvature of the beam is equal to or greater than the curvature of the globe. With such propagation of radio waves, their range of action is many times greater than the line of sight range. In technology, this case of radio wave propagation is called waveguide. Observations confirm the possibility of fairly stable VHF reception at distances up to 1000 km.
Like light waves, radio waves are characterized by the phenomenon of interference or interaction between the phases of radio waves propagating in space. When radio waves that have the same amplitudes but are in antiphase interact, the resulting field will be zero. This phenomenon turns out to be harmful and causes target marks to flicker on the radar screen.
Hydrometeors (rain, fog, clouds, etc.) have a great influence on the propagation of radio waves shorter than 30 cm in the lower layers of the atmosphere. The attenuation of radio waves in water vapor has a particularly strong effect on the centimeter range. The attenuation of radio waves in the atmosphere can significantly reduce the range over long distances. At short distances it has little effect. At millimeter waves, absorption affects certain wavelengths and is determined by the molecular structure of gases entering the atmosphere. Attenuation in the atmosphere must be taken into account for waves shorter than 10 cm, since at these waves the radar range is noticeably reduced in the presence of fog, clouds and rain. Thus, heavy rain causes an attenuation of 0.3–0.4 dB/km for radio waves with a length of 3–5 cm.
Conclusion.
Achievements of science and technology in the field of creating powerful generators of VHF waves (respectively microwave waves) now make it possible to create pulse transmitters that provide the necessary shape and minimum duration of the generated pulses.
The widespread use of microwave waves in radar is explained by the advantages of radio waves in this range.
Literature
1. Ermolaev G.I., Fundamentals of radar and radar equipment of aircraft. - M.: Mechanical Engineering, 1967.
2. Bakulev P.A., Radar of moving targets. – M.: Soviet Radio, 1964.
3. Saibel A.G., Basics of radar. – M.: Soviet Radio, 1961.
Good afternoon, dear Khabrovsk residents.
This post will be about the undocumented functions of the microwave oven. I'll show you how many useful things you can do if you use a slightly modified microwave in an unconventional way.
The microwave contains a generator of microwave waves of enormous power.
The power of the waves that are used in the microwave has been exciting my consciousness for a long time. Its magnetron (microwave generator) produces electromagnetic waves with a power of about 800 W and a frequency of 2450 MHz. Just imagine, one microwave produces as much radiation as 10,000 wi-fi routers, 5,000 mobile phones or 30 mobile phone towers! To prevent this power from escaping, the microwave uses a double protective screen made of steel.I open the case
I want to warn you right away that electromagnetic radiation in the microwave range can harm your health, and high voltage can cause death. But that won't stop me.Removing the cover from the microwave, you can see a large transformer: MOT. It increases the mains voltage from 220 volts to 2000 volts to power the magnetron.
In this video I want to show what this voltage can do:
Antenna for magnetron
After removing the magnetron from the microwave, I realized that I couldn’t just turn it on. The radiation will spread from it in all directions, affecting everything around. Without hesitation, I decided to make a directional antenna from a coffee can. Here's the diagram:Now all the radiation is directed in the right direction. Just in case, I decided to test the effectiveness of this antenna. I took a lot of small neon bulbs and laid them out on a plane. When I brought the antenna with the magnetron on, I saw that the lights were lighting up exactly where needed:
Unusual experiences
I would like to note right away that microwaves have a much stronger effect on technology than on people and animals. Even 10 meters from the magnetron, the equipment experienced severe malfunctions: the TV and music center made a terrible growling sound, the mobile phone first lost the network, and then completely froze. The magnetron had a particularly strong influence on wi-fi. When I brought the magnetron close to the music center, sparks fell from it and, to my surprise, it exploded! Upon closer inspection, I discovered that the mains capacitor had exploded. In this video I show the process of assembling the antenna and the effect of the magnetron on technology:Using non-ionizing radiation from a magnetron, plasma can be obtained. In an incandescent lamp brought to the magnetron, a brightly glowing yellow ball, sometimes with a purple tint, like ball lightning, lights up. If you do not turn off the magnetron in time, the light bulb will explode. Even an ordinary paper clip turns into an antenna under the influence of microwaves. An EMF of sufficient strength is induced on it to ignite an arc and melt this paper clip. Fluorescent lamps and housekeepers light up at a fairly large distance and glow right in your hands without wires! And in a neon lamp, electromagnetic waves become visible:
I want to reassure you, my readers, that none of my neighbors suffered from my experiments. All the closest neighbors fled the city as soon as fighting began in Lugansk.
Safety precautions
I strongly do not recommend repeating the experiments I described because special precautions must be taken when working with microwaves. All experiments were performed solely for scientific and informational purposes. The harm of microwave radiation to humans has not yet been fully studied. When I came close to the working magnetron, I felt heat, like from an oven. Only from the inside and, as it were, pointwise, in waves. I didn't feel any further harm. But I still strongly do not recommend pointing a working magnetron at people. Due to the thermal effect, the protein in the eyes can coagulate and a blood clot may form. There is also debate that such radiation can cause cancer and chronic diseases.Unusual uses of the magnetron
1 - Pest burner. Microwave waves effectively kill pests, both in wooden buildings and on the sunbathing lawn. Bugs have a moisture-containing interior under their hard shell (what an abomination!). Its waves instantly turn into steam, without causing harm to the tree. I tried killing pests on a living tree (aphids, moths), it was also effective, but it is important not to overdo it because the tree also heats up, but not so much.2 - Metal melting. The magnetron power is quite enough for melting non-ferrous metals. You just need to use good thermal insulation.
3 - Drying. You can dry cereals, grains, etc. The advantage of this method is sterilization; pests and bacteria are killed.
4 - Cleaning up from wiretapping. If you treat a room with a magnetron, you can kill all the unwanted electronics in it: hidden video cameras, electronic bugs, radio microphones, GPS tracking, hidden chips and the like.
5 - Jammer. With the help of a magnetron you can easily calm even the noisiest neighbor! The microwave penetrates up to two walls and “calms” any sound equipment.
These are not all possible applications that I have tested. Experiments continue and soon I will write an even more unusual post. Still, I want to point out that using a microwave like this is dangerous! Therefore, it is better to do this in cases of extreme necessity and while observing safety rules when working with microwaves.
That's all for me, be careful when working with high voltage and microwaves.
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 that characterize 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 field. 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 at 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
Many have heard the expression microwave more than once, and have seen these letters on various devices or instructions for them. However, not everyone knows what this abbreviation means. A detailed explanation of microwave will help you better understand the essence of this term and find out in which areas it is used most often.
Ultra high frequency
The literally abbreviated expression stands for ultra-high frequency. For the average person, these words may seem incomprehensible. To better understand what microwave means, you need to have at least a minimum of knowledge from the field of physics. This science studies different types of electromagnetic radiation:
- ultra-long (radio waves);
- terahertz;
- infrared;
- optical;
- ultraviolet;
- hard and x-ray.
Ultra-high frequency waves occupy a space between far-infrared and ultra-high frequencies. Their length forms a wide range from one millimeter to thirty centimeters. Compared to ultra-long radio waves, whose length is measured in hundreds of meters, the size of microwave waves is extremely small, which is why they are also called the centimeter or decimeter range. In foreign literature, ultrahigh frequency radiation is usually called microwave radiation.
The peculiarity of ultra-high frequency waves is that they combine properties inherent in both light radiation and radio waves. For example, just like light rays, microwave waves can be reflected, focused, and propagated in a straight line.
Satellite communications and radar
Another similarity of such radiation with light rays is the ability to transmit information in a mode of increased density. That is, one ultra-high frequency beam can broadcast up to a thousand telephone conversations. This property has made it possible to successfully use microwave radiation:
Another area where it is effective microwave waves are used - this is satellite communication. On land, it is provided by a system of radio towers that broadcast signals over long distances. In the case of intercontinental negotiations, the role of relays is performed by artificial satellites located in the geostationary orbit of the Earth. Each satellite contains thousands of communication channels, guaranteeing the simultaneous transmission of high-quality telephone and television signals to users of modern devices.
Use in everyday life
Surely everyone who has ever wondered what microwave means, how this expression stands for, immediately remembered the microwave oven. This device is perhaps the most famous example of the use of ultrahigh frequency waves in everyday life. It is based on the thermal effect of microwave waves.
This property was accidentally discovered by the American physicist Percy Spencer back in 1942. As a result, three years later, the scientist received a patent for the use of radiation in the cooking process. Within a couple of years, a device weighing more than 300 kg, which was the prototype of a modern microwave oven, appeared in military hospitals and canteens. Over the course of several decades, the device has changed significantly. A microprocessor control system was built into it, and a rotating table appeared. Modern models have the ability to connect to the Internet.
Despite all the modernizations and modifications, the main advantage of the microwave oven was and remains the speed of heating and cooking. This speed is ensured due to the thermal effect of microwaves not only on the surface, but on the entire volume of the product.
The design and principle of operation of a microwave oven
The design of a microwave oven cannot be called overly complex. Its design consists of:
Uniform heating of food in the oven is ensured by the rotation of a special table. A built-in fan helps avoid overheating during operation, and electronic circuits make operating the microwave as convenient and safe as possible.
Heating of products placed in a metal chamber occurs due to exposure to powerful rays with a frequency of 2450 MHz. Penetrating inside to a depth of about 3 cm, these rays set in motion polar molecules, which are present in large quantities in all food products. As a result of the intense movement of molecules, food quickly heats up.
While the microwave is operating the temperature inside the chamber reaches very high values Therefore, the design includes a special element that protects the device from overheating - a thermal fuse (thermal relay). The main part of a thermal relay is a bimetallic plate that can change shape under the influence of temperature.
When the heating level reaches the limit values, the plate changes shape and forces the pusher to act, which opens the connection of the contact group plates and stops the operation of the microwave oven. As the temperature decreases, the regulator plate returns to its original position, the contacts close, and the device begins to operate again.
In addition to domestic use, furnaces operating on the basis of microwave radiation have found application in industry. They are used for processing building materials, softening rocks, oil reclamation, etc.
Microwave stands for “ultra-high frequencies.” Many will think that this is something complicated from the field of abstruse physics and mathematics, and that this does not concern them. However, the situation is completely different. Microwave devices have long been an integral part of our lives, and they can be found everywhere. But what is it?
Ultra high frequency range
Explanation Microwave - ultra-high frequencies of electromagnetic radiation, which are located in the spectrum between the frequency of the infrared far region and ultra-high frequencies. this range is from thirty centimeters to one millimeter. That is why microwaves are sometimes called centimeter and decimeter waves. In foreign technical literature, microwave decoding is the microwave range. This means that the wavelength is very small compared to radio broadcast waves, which are on the order of several hundred meters.
Properties of the microwave range
In terms of its length, this type of waves is intermediate between the emission of light and radio signals, therefore it has the properties of both types. For example, like light, these waves travel along a straight path and are blocked by almost all more or less solid objects. Similar to light, it can focus, be reflected, and spread in the form of rays. Despite the fact that microwave decoding focuses on the “ultra”-high range, many antennas and radar devices are a slightly enlarged version of mirrors, lenses and other optical elements.
Generation
Since ultrahigh frequency radiation is similar to radio waves, it is generated by similar methods. Decoding microwaves involves applying the classical theory of radio waves to it, however, thanks to the increased range, it is possible to increase the efficiency of its use. For example, just one beam can “carry” up to a thousand telephone conversations simultaneously. The similarities between microwave waves and light, expressed in an increased density of transmitted information, have proven useful for radar technology.
Application of ultrahigh frequencies in radar
Waves in the centimeter and decimeter ranges became a subject of interest during the Second World War. At that time, there was a need for an effective and innovative detection tool. Then microwave waves were studied for their use in radar. The idea is that intense and short pulses are launched into space, and then some of these rays are recorded after returning from the desired distant objects.
Application of ultrahigh frequencies in the field of communications
As we have already said, microwave decoding is ultra-high frequencies. Engineers and technicians decided to use these radio waves in communication. All countries actively use commercial communication lines based on the transmission of high-band waves. Such radio signals do not travel along the curve of the earth's surface, but in a straight line, through relay communication stations located at altitudes at intervals of about fifty kilometers.
Transmission does not require large amounts of electricity, since microwave waves allow highly targeted reception and transmission, and are also amplified at stations by electronic amplifiers before retransmission. A system of antennas, towers, transmitters and receivers seems expensive, but it all pays off with the information capacity of such
Application of ultrahigh frequencies in the field of satellite communications
A system of radio towers for relaying microwave signals over long distances can only exist on land. For intercontinental negotiations, artificial satellites are used, which are located on Earth and serve as relays. Each satellite provides several thousand high-quality satellites to its customers to transmit television and telephone signals simultaneously.
Heat treatment of products
The first attempts to use ultrahigh frequencies for food processing received positive and even enthusiastic reviews. Microwave ovens today are used both at home and in the large food industry. The energy generated by high-power electronic lamps is concentrated in a small volume, which allows thermal processing of products cleanly, compactly and silently.
It is most widespread in the household and can be found in many kitchens. Also, similar devices for household use are used in all places where quick heating and preparation of dishes is necessary. A microwave oven with grill, for example, is an absolutely necessary element for any self-respecting restaurant.
Main sources of radiation
Progress in the use of microwave waves is associated with the klystron and magnetron, which are capable of generating huge amounts of high-frequency energy. The use of a magnetron is based on the principle of a volumetric resonator, the walls of which are inductance, and the space between the walls is the capacitance of the resonant circuit. The dimensions of this element are selected according to the required resonant ultra-high frequency, which would correspond to the desired ratio between capacitance and inductance.
So, the decoding of microwave is ultra-high frequencies. The size of the generator directly affects the power of such radiation. Small magnetrons for high frequencies are so small that their powers cannot reach the required values. The problem also arises with the use of heavy magnets. In a klystron it is partially solved, since this electric vacuum device does not require an external field.
Loading...