The second part of the article is devoted to ways to see what is beyond the horizon.
After reading the comments to, I decided to talk in more detail about VSD communications and radars based on the principles of the “heavenly beam”; about radars operating on the principles of the “earth beam” will be in the next article, if I talk about it then I’ll talk about it sequentially.
Over-the-horizon radars, an engineer’s attempt to explain the complex in simple terms. (part two) "Russian Woodpecker", "Zeus" and "Antey".
INSTEAD OF A FOREWORD
In the first part of the article, I explained the basics necessary for understanding. Therefore, if suddenly something becomes unclear, read it, learn something new or refresh something forgotten. In this part, I decided to move from theory to specifics and tell the story based on real examples. For examples, in order to avoid stuffing, misinformation and inciting the farts of armchair analysts, I will use systems that have been in operation for a long time and are not secret. Since this is not my specialization, I am telling you what I learned when I was a student from teachers in the subject “Fundamentals of Radiolocation and Radio Navigation,” and what I dug up from various sources on the Internet. Comrades are well versed in this topic, if you find an inaccuracy, constructive criticism is always welcome.
"RUSSIAN WOODPECKER" AKA "ARC"
"DUGA" is the first over-the-horizon radar in the union (not to be confused with over-the-horizon radars) designed to detect ballistic missile launches. Three stations of this series are known: Experimental installation “DUGA-N” near Nikolaev, “DUGA-1” in the village of Chernobyl-2, “DUGA-2” in the village of Bolshaya Kartel near Komsomolsk-on-Amur. On at the moment all three stations have been decommissioned; their electronic equipment has been dismantled and also dismantled antenna arrays except for the station located in Chernobyl. The antenna field of the DUGA station is one of the most noticeable structures in the exclusion zone after the building of the Chernobyl nuclear power plant itself.
Antenna field "ARC" in Chernobyl, although it looks more like a wall)
The station operated in the HF range at frequencies of 5-28 MHz. Please note that the photo shows, roughly speaking, two walls. Since it was impossible to create one sufficiently broadband antenna, it was decided to divide the operating range into two antennas, each designed for its own frequency band. The antennas themselves are not one solid antenna, but consist of many relatively small antennas. This design is called a Phased Array Antenna (PAR). In the photo below there is one segment of such a PAR:
This is what one segment of the "ARC" HEADLIGHTS looks like, without supporting structures.
Arrangement of individual elements on the supporting structure
A few words about what PAR is. Some asked me to describe what it is and how it works, I was already thinking about starting, but I came to the conclusion that I would have to do this in the form of a separate article, since I need to tell a lot of theory for understanding, so an article about phased array will be in the future. And in a nutshell: the phased array allows you to receive radio waves coming at it from a certain direction and filter out everything that comes from other directions, and you can change the direction of reception without changing the position of the phased array in space. What is interesting is that these two antennas, in the photographs from above, are receiving, that is, they could not transmit (radiate) anything into space. There is a mistaken opinion that the emitter for the "ARC" was the nearby "CIRCLE" complex, this is not so. The VNZ "KRUG" (not to be confused with the KRUG air defense system) was intended for other purposes, although it worked in tandem with the "ARC", more about it below. The arc emitter was located 60 km from Chernobyl-2 near the city of Lyubech (Chernigov region). Unfortunately I couldn't find one authentic photograph of this object, there is only a verbal description: “The transmitting antennas were also built on the principle of a phased array antenna and were smaller and lower, their height was 85 meters.” If anyone suddenly has photographs of this structure, I would be very grateful. The receiving system of the air defense radar "DUGA" consumed about 10 MW, but I can’t say how much the transmitter consumed because the numbers are very different in different sources, I can say offhand that the power of one pulse was no less than 160 MW. I would like to draw your attention to the fact that the emitter was pulsed, and it was precisely these pulses that the Americans heard on their air that gave the name to the station “Woodpecker”. The use of pulses is necessary so that with their help it is possible to achieve more radiated power than the constant power consumption of the emitter. This is achieved by storing energy in the period between pulses, and emitting this energy in the form of a short-term pulse. Typically, the time between pulses is at least ten times longer than the time of the pulse itself. It is this colossal energy consumption that explains the construction of the station in relative proximity to a nuclear power plant - the source of energy. This is how the “Russian woodpecker” sounded by the way on American radio. As for the capabilities of the "ARC", stations of this type could only detect a massive rocket launch during which a large number of torches of ionized gas were formed from the rocket engines. I found this picture with the viewing sectors of three “DUGA” type stations:
This picture is correct partly because it only shows the viewing directions, and the viewing sectors themselves are not marked correctly. Depending on the state of the ionosphere, the viewing angle was approximately 50-75 degrees, although in the picture it is shown at a maximum of 30 degrees. The viewing range again depended on the state of the ionosphere and was no less than 3 thousand km, and in the best case it was possible to see launches right beyond the equator. From which it could be concluded that the stations scanned the entire territory of North America, the Arctic, and the northern parts of the Atlantic and Pacific oceans, in a word, almost all possible areas for launching ballistic missiles.
VNZ "CIRCLE"
For correct operation For radar and determining the optimal path for the sounding beam, it is necessary to have accurate data on the state of the ionosphere. To obtain this data, the “CIRCLE” station for Reverse Oblique Sounding (ROS) of the ionosphere was designed. The station consisted of two rings of antennas similar to HEADLIGHTS "ARC" only located vertically, there were a total of 240 antennas, each 12 meters high, and one antenna stood on a one-story building in the center of the circles.
VNZ "CIRCLE"
Unlike "ARC", the receiver and transmitter are located in the same place. The task of this complex was to constantly determine the wavelengths that propagate in the atmosphere with the least attenuation, the range of their propagation and the angles at which the waves are reflected from the ionosphere. Using these parameters, the path of the beam to the target and back was calculated and the receiving phased array was configured in such a way that it would receive only its reflected signal. In simple words, the angle of arrival of the reflected signal was calculated and the maximum sensitivity of the phased array was created in this direction.
MODERN air defense systems "DON-2N" "DARYAL", "VOLGA", "VORONEZH"
These stations are still on alert (except for Daryal), there is very little reliable information on them, so I will outline their capabilities superficially. Unlike "DUGI", these stations can record individual missile launches, and even detect cruise missiles flying at very low speeds. In general, the design has not changed; these are the same phased arrays used for receiving and transmitting signals. The signals used have changed, they are the same pulse ones, but now they are spread evenly across the operating frequency band, in simple words This is no longer the knock of a woodpecker, but a uniform noise that is difficult to distinguish from the background of other noise without knowing the original structure of the signal. The frequencies also changed; if the arc operated in the HF range, then “Daryal” is capable of operating in HF, VHF and UHF. Targets can now be identified not only by gas exhaust but also by the target carcass itself; I already talked about the principles of detecting targets against the background of the ground in the previous article.
LONG LONG VHF RADIO COMMUNICATION
In the last article I briefly talked about kilometer waves. Maybe in the future I’ll do an article on these types of communications, but now I’ll briefly tell you using the examples of two ZEUS transmitters and the 43rd communications center of the Russian Navy. The title SDV is purely symbolic, since these lengths fall outside the generally accepted classifications, and systems using them are rare. ZEUS uses waves with a length of 3656 km and a frequency of 82 hertz. A special antenna system is used for radiation. Find a piece of land with the lowest possible conductivity, two electrodes are driven into it at a distance of 60 km to a depth of 2-3 km. For radiation, a high-voltage voltage is applied to the electrodes with a given frequency (82 Hz), since the resistance of the earth’s rock is extremely high between the electrodes, electric current you have to go through the deeper layers of the earth, thereby turning them into a huge antenna. During operation, Zeus consumes 30 MW, but the emitted power is no more than 5 Watts. However, these 5 Watts are completely enough for the signal to travel completely through the entire globe; the work of Zeus is recorded even in Antarctica, although it itself is located on the Kola Peninsula. If you adhere to the old Soviet standards, "Zeus" operates in the ELF (extremely low frequency) range. The peculiarity of this type of communication is that it is one-way, so its purpose is to transmit conditional short signals, upon hearing which, submarines float to a shallow depth to communicate with the command center or release a radio buoy. Interestingly, Zeus remained secret until the 1990s, when scientists at Stanford University (California) published a number of intriguing statements regarding research in the field of radio engineering and radio transmission. Americans have witnessed an unusual phenomenon - scientific radio equipment located on all continents of the Earth regularly, at the same time, records strange repeating signals at a frequency of 82 Hz. The transmission speed per session is three digits every 5-15 minutes. The signals come directly from the earth's crust - researchers have a mystical feeling as if the planet itself is talking to them. Mysticism is the lot of medieval obscurantists, and the advanced Yankees immediately realized that they were dealing with an incredible ELF transmitter located somewhere on the other side of the Earth. Where? It is clear where - in Russia. It looks like these crazy Russians have short-circuited the entire planet, using it as a giant antenna to transmit encrypted messages.
The 43rd communications center of the Russian Navy presents a slightly different type of long-wave transmitter (radio station "Antey", RJH69). The station is located near the town of Vileika, Minsk region, Republic of Belarus, the antenna field covers an area of 6.5 square kilometers. It consists of 15 masts 270 meters high and three masts 305 meters high, with antenna field elements stretched between the masts, the total weight of which is about 900 tons. The antenna field is located above wetlands, which provides good conditions for signal radiation. I myself was next to this station and I can say that just words and pictures cannot convey the size and sensations that this giant evokes in reality.
This is what the antenna field looks like on Google maps; the clearings over which the main elements are stretched are clearly visible.
View from one of the Antea masts
The power of "Antey" is at least 1 MW, unlike air defense radar transmitters, it is not pulsed, that is, during operation it emits this same mega watt or more, all the time it is operating. The exact information transmission speed is not known, but if we draw an analogy with the German captured Goliath, it is no less than 300 bps. Unlike the Zeus, communication is already two-way; submarines for communication use either many-kilometer towed wire antennas, or special radio buoys that are released by the submarine from great depths. The VHF range is used for communication; the communication range covers the entire northern hemisphere. The advantages of SDV communication are that it is difficult to jam it with interference, and it can also work in conditions nuclear explosion and after it, while higher frequency systems cannot establish communication due to interference in the atmosphere after the explosion. In addition to communication with submarines, "Antey" is used for radio reconnaissance and transmitting precise time signals of the "Beta" system.
INSTEAD OF AN AFTERWORD
This is not the final article about the principles of looking beyond the horizon, there will be more, in this one, at the request of readers, I focused on real systems instead of theory.. I also apologize for the delay in the release, I’m not a blogger or a resident of the Internet, I have a job that I love and which periodically “loves” me very much, so I write articles casually. I hope it was interesting to read, because I am still in trial mode and have not yet decided what style to write in. Constructive criticism is welcome as always. Well, and especially for philologists, an anecdote at the end:
Matan teacher about philologists:
-...Spit in the face of anyone who says that philologists are tender violets with sparkling eyes! I beg you! In fact, they are gloomy, bilious types, ready to tear out the tongue of their interlocutor for phrases like “pay for water”, “it’s my birthday”, “there is a hole in my coat”...
Voice from the back:
- What's wrong with these phrases?
The teacher adjusted his glasses:
“And on your corpse, young man, they would even jump.”
The invention relates to the field of radio engineering, namely to antenna technology and can be used as a broadband antenna system with a controlled radiation pattern when providing radio communications with ionospheric waves in the HF and VHF ranges. The purpose of the invention is to develop an antenna system that, with one standard size, ensures the operation of wide-range transmitters that require high quality matching with the antenna. A phased array antenna (PAA) consists of identical flat elements, each of which is formed by a pair of orthogonal coplanar vibrators of length L with triangular arms 1 (the value of L is equal to the minimum wavelength in the operating range). The central element and connected to it by means of a short circuit. conductors and 2 peripheral elements form an orthogonal pair of low-frequency range vibrators. All peripheral elements, including those included in the low-frequency vibrator, form the high-frequency phased array. Excitation of the antenna system is separate for horizontal (g-g") and (v-v") vibrators, but it is also possible to be combined in order to realize circularly polarized radiation. The phased array provides operation in a 40-fold range at a BEV level of at least 0.5. 6 ill.
The invention relates to the field of radio engineering, namely to antenna technology and, in particular, can be used as a transceiver underground or creeping antenna system for operating ionospheric waves in the HF and VHF ranges. Known underground and surface antennas of the HF and VHF ranges (Sosunov B.V. Filippov V.V. Fundamentals of calculation of underground antennas. L. VAS, 1990). Multi-section underground analogue antennas are made in the form of a group of parallel in-phase isolated vibrators. To increase the gain, several such groups are used, placed one after another and phased accordingly. The disadvantages of the known analogs are a narrow range of operating frequencies due to sudden changes in input impedance, a limited beam scanning sector, and large dimensions. To ensure operation in the required range and given directions, it is necessary to have several standard sizes. The closest in its technical essence to the claimed phased array antenna (PAR) is the well-known SGDP 3.6/4 RA PAR (Eisenberg G.Z. et al. Short-wave antennas. M. Radio and Communications, 1985, pp. 271-274, Fig. 13.11.). The prototype antenna consists of a group of flat elements (PE) made of metal conductors. Each PE is a radiator in the form of a symmetrical vibrator made of two triangular arms, the outer ends of which are connected by a short-circuit. conductors. All elements are united by a common feeder path and form an in-phase or phased (if phasing devices are included in the feeder path) array. The elements are located coplanarly within the rectangle that limits the aperture of the phased array and are suspended vertically on the masts of the phased array. Thanks to the use of elements consisting of emitters with triangular arms, it has a wide range of operating frequencies and better matching. However, the prototype has disadvantages. The operating range overlap coefficient (the ratio of the maximum operating frequency to the minimum) of the SGDP 3.6/4 RA antenna array is equal to 2.14, which is significantly less than the value of this parameter for modern transmitters and does not allow one standard size to be used when providing communications on different distances. The control sector of the radiation pattern (DP) in the horizontal plane, equal to 60 o, limits the capabilities of this antenna when operating in a radio network. In addition, the antenna has large dimensions and low security, and does not provide independent operation with vertical and horizontal polarization or a circularly polarized wave. The objective of the invention is to create a broadband phased array intended for use as a ground or underground antenna for the HF and VHF ranges, providing control of the radiation pattern in the entire upper half-space while reducing the size of the radiating surface. The task is achieved by the fact that in a known phased array containing a group of PEs, each of which includes a pair of triangular emitters installed coplanarly within the rectangle limiting the aperture of the phased array and connected to the feeder path, an additional pair of identical emitters installed coplanarly and orthogonal to the first. All PEs are located horizontally within the semiconducting medium or on its surface. The outer ends of the triangular emitters belonging to the PEs adjacent to each other are electrically connected. The outer ends of the triangular emitters belonging to the peripheral PEs are connected along the perimeter of the phased array aperture by additional short circuits. conductors. The outer ends of the triangular emitters, adjacent on both sides to large diagonals The phased arrays are electrically isolated, and the outer ends of the remaining triangular emitters are connected by short-circuited conductors. The feeder path of the LF channel is connected to the tops of the triangular emitters of the PE located in the center of the phased array. The tops of the triangular emitters of the remaining PEs are connected to the feeder path of the RF channel. Orthogonal emitters in each PE are powered independently, i.e. can excite either each separately with linear polarization, or with a shift of 90 o, thereby achieving circularly polarized radiation. With such a phased array scheme, the same elements are used twice to operate in both the LF and HF ranges (with an overlap coefficient of 5.33 and 7.5, respectively) with matching at the BV level of at least 0.5. In general, the proposed phased array operates in a range with 40-fold overlap. Moreover, at the resonant frequency, the area of its emitting surface is 1.6 times less than that of the prototype. In fig. 1 shows a general view of the phased array; in fig. 2 flat element; in fig. 3 four- and three-shunt PE; in fig. 4 feeder system; in fig. 5, 6 - results of experimental studies. The phased array shown in Fig. 1, consists of N (for example, N 9 is taken) identical PEs. An embodiment of the PE is shown in Fig. 2. Each PE is formed by an orthogonal pair of flat vibrators z-g" and b-v" of length 2L 1 with arms in the form of equilateral triangles 1. The adjacent ends of the triangular emitters of neighboring PEs are electrically connected ( m-m lines"). The peripheral ends of the triangular emitters PE are connected short-circuit by conductors 2 (Fig. 3), with the exception of the triangular emitters adjacent on both sides to the large diagonals c-c" and p-p", i.e. these emitters are electrically isolated (Fig. 3). Under this condition, the central PE short circuit. conductors no less (Fig. 2). The ends of the triangular emitters c-c" and d-g", located on the outer edges of the phased array, are additionally connected by conductors 3 (in this case, each conductor 3 together with two conductors forms a closed circuit, which can be filled with additional conductors or replaced with a solid metal plate of the same forms). Each PE has transverse and longitudinal dimensions 2L= min (where min is the minimum wavelength in the operating range), and in general the phased array is a square with a side 
. The phased array feeder system shown in FIG. 4, consists of two identical groups feeding horizontal y-y" And vertical in-in"PE emitters. Fig. 1 shows the feeder group of horizontal emitters. It includes feeder 4 of the LF vibrator and (N-1) feeders of 5 HF vibrators. Screen shells 6 of feeders 4, 5 are electrically connected to the tops of the left triangular emitters of horizontal vibrators, and the central conductors 7 of these feeders are connected in the same way to the right triangular emitters. Feeder 4 of the LF element is connected directly to the transmitter (receiver). Feeders 5 of the HF elements are connected through controlled delay lines (ULZ) 8 and a divider to ensure phasing of the antenna array and interface with the output of the transmitter. power 9 (when working with a 1:8 coupling device). The proposed device operates as follows when an excitation voltage is supplied through the feeder 4 k. points y-y"(for a vertical vibrator b-c"), the current from the indicated points flows along the rhombic-shaped arms formed by interconnected triangular emitters 1 of the central and side PE, as well as from points E and E" through conductors 2 to points H and H" orthogonal triangular emitters of peripheral PEs, then along them in the transverse direction to points K and K", from each of which there are pairs of conductors 2 located on the outer side of the phased array (or plates replacing them). To operate the phased array in the HF range, the transmitter power in the divider 9 is divided by 8 identical channels, in each of which the required phase shift is created using the ULZ 8, and then the PE is excited through the feeders 5. When the excitation voltage is applied to the input of one of the vibrators (horizontal or vertical) of each PE, the other vibrator together with the conductors forms a voltage. .h. a jumper connecting the ends of the excited emitter, thereby achieving improved matching in the lower part of the range. Experimental studies of the proposed phased array were carried out on a prototype designed to operate in the range of 1.5-60 MHz, made of sheet steel 2 mm thick. The layout dimensions are 15 x 15 m2, the soil is dry (=5, =0.001 S/m). The HF PAR feeder system was made of coaxial cables RK-75-9-12 with a length of (140-0.1) m, excitation of the LF elements was carried out via cables RK-75-17-12 with a length of (120-0.1) m. the circuit included a 1:8 transformer power divider and an 8-channel 4-bit controlled delay line formed by segments coaxial cable with fluoroplastic insulation lengths of 0.66 m, 1.32 m, 2.64 m and 5.28 m. The Fakel-N1 product was used as a transmitting device (operating frequency range 1.5-60 MHz, power up to 4 kW ). During the research, the input impedances of low-frequency elements, high-frequency elements separately and as part of a phased array were measured, from which the BEF values and such dynamic radiation patterns at various frequencies were calculated. The values of KBV, low-frequency element, individual high-frequency element and phased array as a whole, shown in Fig. 5, confirm high quality coordination throughout the entire operating range. The dynamic radiation patterns of the phased array in the lower, middle and upper parts of the range are shown in Fig. 6 (graphs a, b, c, respectively). The solid line shows the calculated patterns, the crosses show the measurement results. It can be seen that, over the entire range, the phased array ensures the formation of a maximum radiation in a given direction.
Formula of invention
A phased array antenna containing a group of flat elements, each of which includes a pair of triangular emitters installed coplanarly within a rectangle delimiting the aperture of the phased antenna array, and connected to the feeder path, characterized in that the flat elements are located horizontally within the semiconducting medium or on it surface, a second pair of identical emitters is inserted into each flat element, installed coplanarly and orthogonally to the first, the outer ends of triangular emitters belonging to adjacent flat elements are electrically connected, and the outer ends of triangular emitters belonging to peripheral flat elements are connected along the perimeter of the phased aperture antenna array with additional short-circuiting conductors, and the outer ends of the triangular emitters adjacent on both sides to the large diagonals of the phased antenna array are electrically isolated, and the outer ends of the remaining triangular emitters are connected by short-circuiting conductors, while the feed path of the low-frequency channel is connected to the tops of the triangular emitters of the flat element, located in the center of the phased antenna array, and the tops of the triangular emitters of the remaining flat elements are connected to the feeder path high frequency channel, and the orthogonal triangular emitters in each flat element are powered independently.
In the previous publication /1/ we showed that in conditions where it is not possible to raise the antenna to a significant height, antennas with vertical polarization and a small radiation angle have an advantage when conducting long-distance communications: vertical curved dipole (Fig. 1), vertical Moxon ( fig.2)We deliberately do not mention here verticals with a system of counterweights or radials, since these antennas are very inconvenient for placement in summer cottages or in expeditionary conditions.
The vertical Moxon (Fig. 2), although a good directional antenna with a small radiation angle, still has insufficient gain compared to multi-element “wave channels” or “squares”. Therefore, we naturally had a desire to try a phased array of two vertical Moxons, similar to that used by American radio amateurs on an expedition to Jamaica (they called it “2x2”) /2/.
The simplicity of its design and the small space required for its placement make the task easily feasible. The experiment was carried out on the 17 m band (central frequency 18.120 MHz), since we already had one vertical Moxon for this range. Its calculated characteristics (Fig. 3): gain 4.42 dBi, back lobe suppressed by more than 20 dB, maximum radiation at an angle of 17 degrees, almost pure vertical polarization of radiation. And this is with the height of the lower edge of the antenna only 2 m above the real ground.
For each of the antennas you will need a dielectric mast 8 - 10 m high (or a tree of a suitable height) and two (preferably three) dielectric spacers 2.2 m long (wooden slats can be used). Elements - from any copper wire, 1-3 mm in diameter, bare or insulated.
During the experiment, a set of fiberglass pipes from RQuad with a total height of 10 m was used as a mast, and plastic water pipes with a diameter of 20 mm were used as spacers. The elements are made from vole wire. Guys are made of 3 mm polypropylene cord. The result is the design shown in Fig. 4.
Fig.3. Design characteristics of Moxon vertical antenna.
The wire is passed through the holes near the ends of the spacers and secured to them using electrical tape or plastic clamps. To prevent the spacers from bending under the weight of the antenna, their ends are stretched with fishing line. To maintain the straightness of the active element, which is disrupted due to the weight of the cable, you can use a third spacer at the level of the middle of the elements, passing the director wire through the hole in it and securing the connection points of the active element to the cable on it. The cable runs along the spreader to the mast and then down the mast. The cable is equipped with ferrite tubes every 2 m, eliminating the influence of its braid on the characteristics of the antenna and at the same time balancing the supply currents. The antenna is easily lifted onto a pre-installed mast with a roller on top using a nylon cord.
The characteristics of a horizontal stack of two such antennas, calculated using the MMANA program, are shown in Fig. 5. Best Features in terms of amplification and suppression of the back lobe were obtained at a distance between the antennas of 0.7 wavelengths, i.e. 11.6 m. This antenna can be called "2×MOXON".
Fig.5. Radiation pattern of a phased array of two vertical Moxon antennas.
The summation circuit is classic: since each antenna has an input impedance of 50 Ohms, power cables with a resistance of 75 Ohms, ¾ wavelength long, are used, taking into account the cable shortening factor. At the ends of the cables, the antenna resistance transforms to 100 ohms. Therefore, they can be connected in parallel using a tee, followed by a 50 Ohm power cable of any length. The length of the transforming cables was chosen to be ¾ wavelength, since at a length of ¼ wavelength their lengths are not enough to cover the distance between the antennas.
It took us about two hours to make the second copy of this antenna. The masts were installed with a spacing of 11.6 m (the width of the summer cottage was sufficient).
Each antenna was tuned separately, connecting them via a half-wavelength cable (taking into account shortening), and trimming the ends of the lower bent parts of the elements. To avoid errors in configuration, it is necessary to pay special attention to the suppression of common-mode currents in power cables using chokes placed on the cable. We had to use up to 10 pieces. of snap-on ferrite filters distributed along the length of the 75 ohm cable before the results stabilized. These chokes must also be on transforming cables connected by a tee. It is not necessary to put chokes on the 50 Ohm cable connecting the tee to the transceiver. In the absence of ferrites, the chokes can be replaced with several turns of cable assembled into a coil with a diameter of 15-20 cm, placing them near the antenna feed points and near the tee. To improve the performance of antennas, almost the entire free length of transforming cables can be assembled into choke coils.
After connecting two vertical Moxons into a lattice resonant frequency goes up by about 500 kHz, and the SWR at the center frequency becomes equal to 1.4.
It is impossible to correct the resonance of the system by adjusting the Moxons, because in this case the directional pattern falls apart. Most simple ways system matching - either connecting coils with an inductance of 0.2 μH in series with the inputs of both antennas, or one capacitor 400-550 pF (select the value for the minimum SWR at the center frequency) in series with the input of the tee on the 50 Ohm feeder side. In this case, the band according to the SWR level< 1,2 получается около 200 кГц (рис.6).
Fig.6. SWR from the input after adjustment using 0.2 µH inductors.
Calculated parameters at a height of the lower edge of the antennas 2 m above the real ground:
Gain 8.58 dBi (6.43 dBd),
Elevation angle 17 degrees,
Back lobe suppression >25 dB,
SWR in operating range< 1,2.
The presence of side lobes with a suppression of 10 dB relative to the main one is not, in our opinion, a disadvantage, because allows you to hear stations outside the narrow main beam without turning the antenna.
We are not aware of other antenna designs that have such high parameters with such design simplicity.
Of course, this phased array is stationary and should be installed in the direction of the most interesting DX (to the west, for example). Then turning its diagram to the east will not be difficult: to do this, you need to lower the antennas, rotate them 180 degrees and raise them again to the masts. For us, this operation took no more than five minutes after some training.
A photo of the experimental antenna is shown in Fig. 7.
Fig.7. View of a phased array of two vertical Moxons.
Vladislav Shcherbakov, (RU3ARJ)
Sergey Filippov, (RW3ACQ)
Yuri Zolotov, (UA3HR)
Literature:
1. Vladislav Shcherbakov RU3ARJ, Sergey Filippov RW3ACQ. Symmetrical vertical antennas are the optimal solution for DX communications in field and country conditions. Materials of the Forum of the Festival “Domodedovo 2007”.
2. K5K Kingman Reef DXpedition.
www.force12inc.com/k5kinfo.htm
info - http://cqmrk.ru
The article for translation was proposed by alessandro893. The material is taken from an extensive reference site, describing, in particular, the principles of operation and design of radars.
An antenna is an electrical device that converts electricity into radio waves and vice versa. The antenna is used not only in radars, but also in jammers, radiation warning systems and communications systems. During transmission, the antenna concentrates the energy of the radar transmitter and forms a beam directed in the desired direction. When receiving, the antenna collects the returning radar energy contained in the reflected signals and transmits them to the receiver. Antennas often vary in beam shape and efficiency.
Left – isotropic antenna, right – directional
Dipole antenna
A dipole antenna, or dipole, is the simplest and most popular class of antennas. Consists of two identical conductors, wires or rods, usually with bilateral symmetry. For transmitting devices, current is supplied to it, and for receiving devices, a signal is received between the two halves of the antenna. Both sides of the feeder at the transmitter or receiver are connected to one of the conductors. Dipoles are resonating antennas, that is, their elements serve as resonators in which standing waves pass from one end to the other. So the length of the dipole elements is determined by the length of the radio wave.
Radiation scheme
Dipoles are omnidirectional antennas. For this reason, they are often used in communication systems.
Antenna in the form of an asymmetric vibrator (monopole)
An asymmetrical antenna is half of a dipole antenna, and is mounted perpendicular to the conducting surface, a horizontal reflecting element. The directivity of a monopole antenna is twice that of a double-length dipole antenna because there is no radiation underneath the horizontal reflective element. In this regard, the efficiency of such an antenna is twice as high, and it is capable of transmitting waves further using the same transmission power.
Radiation scheme
Wave channel antenna, Yagi-Uda antenna, Yagi antenna
Radiation scheme
Corner antenna
A type of antenna often used on VHF and UHF transmitters. It consists of an irradiator (this can be a dipole or a Yagi array) mounted in front of two flat rectangular reflective screens connected at an angle, usually 90°. A sheet of metal or a grating (for low-frequency radars) can act as a reflector, reducing weight and increasing wind resistance. Corner antennas have a wide range, and the gain is about 10-15 dB.
Radiation scheme
Vibrator log-periodic (logarithmic periodic) antenna, or log-periodic array of symmetrical vibrators
A log-periodic antenna (LPA) consists of several half-wave dipole emitters of gradually increasing length. Each consists of a pair of metal rods. The dipoles are attached closely, one behind the other, and connected to the feeder in parallel, with opposite phases. This antenna looks similar to the Yagi antenna, but it works differently. Adding elements to a Yagi antenna increases its directivity (gain), and adding elements to an LPA increases its bandwidth. Its main advantage over other antennas is its extremely wide range of operating frequencies. The lengths of the antenna elements relate to each other according to a logarithmic law. The length of the longest element is 1/2 the wavelength of the lowest frequency, and the shortest is 1/2 the wavelength of the highest frequency.
Radiation scheme
Helix antenna
A helical antenna consists of a conductor twisted into a spiral. They are usually mounted above a horizontal reflective element. The feeder is connected to the bottom of the spiral and the horizontal plane. They can operate in two modes - normal and axial.
Normal (transverse) mode: The helix dimensions (diameter and inclination) are small compared to the wavelength of the transmitted frequency. The antenna operates in the same way as a shorted dipole or monopole, with the same radiation pattern. The radiation is linearly polarized parallel to the axis of the spiral. This mode is used in compact antennas for portable and mobile radios.
Axial mode: the dimensions of the spiral are comparable to the wavelength. The antenna works as a directional one, transmitting the beam from the end of the spiral along its axis. Emits radio waves of circular polarization. Often used for satellite communications.
Radiation scheme
Rhombic antenna
A diamond antenna is a broadband directional antenna consisting of one to three parallel wires fixed above the ground in the shape of a diamond, supported at each vertex by towers or poles to which the wires are attached using insulators. All four sides of the antenna are the same length, usually at least the same wavelength, or longer. Often used for communication and operation in the decameter wave range.
Radiation scheme
Two-dimensional antenna array
Multi-element array of dipoles used in the HF bands (1.6 - 30 MHz), consisting of rows and columns of dipoles. The number of rows can be 1, 2, 3, 4 or 6. The number of columns can be 2 or 4. The dipoles are horizontally polarized and a reflective screen is placed behind the dipole array to provide an amplified beam. The number of dipole columns determines the width of the azimuthal beam. For 2 columns the beam width is about 50°, for 4 columns it is 30°. The main beam can be tilted 15° or 30° for maximum coverage of 90°.
The number of rows and the height of the lowest element above the ground determines the elevation angle and the size of the serviced area. An array of two rows has an angle of 20°, and an array of four has an angle of 10°. The radiation from a two-dimensional array usually approaches the ionosphere at a slight angle, and due to its low frequency, is often reflected back to the earth's surface. Since radiation can be reflected many times between the ionosphere and the ground, the antenna's action is not limited to the horizon. As a result, such an antenna is often used for long-distance communications.
Radiation scheme
Horn antenna
A horn antenna consists of an expanding horn-shaped metal waveguide that collects radio waves into a beam. Horn antennas have a very wide range of operating frequencies; they can operate with a 20-fold gap in its boundaries - for example, from 1 to 20 GHz. The gain varies from 10 to 25 dB, and they are often used as feeds for larger antennas.
Radiation scheme
Parabolic antenna
One of the most popular radar antennas is the parabolic reflector. The feed is located at the focus of the parabola, and the radar energy is directed to the surface of the reflector. Most often, a horn antenna is used as a feed, but both a dipole and a helical antenna can be used.
Since the point source of energy is at the focus, it is converted into a wavefront of constant phase, making the parabola well suited for use in radar. By changing the size and shape of the reflective surface, beams and radiation patterns of various shapes can be created. The directivity of parabolic antennas is much better than that of a Yagi or dipole; the gain can reach 30-35 dB. Their main drawback is their inability to handle low frequencies due to their size. Another thing is that the irradiator can block part of the signal.
Radiation scheme
Cassegrain antenna
A Cassegrain antenna is very similar to a conventional parabolic antenna, but uses a system of two reflectors to create and focus the radar beam. The main reflector is parabolic, and the auxiliary reflector is hyperbolic. The irradiator is located at one of the two foci of the hyperbola. The radar energy from the transmitter is reflected from the auxiliary reflector onto the main one and focused. The energy returning from the target is collected by the main reflector and reflected in the form of a beam converging at one point onto the auxiliary one. It is then reflected by an auxiliary reflector and collected at the point where the irradiator is located. The larger the auxiliary reflector, the closer it can be to the main one. This design reduces the axial dimensions of the radar, but increases the shading of the aperture. A small auxiliary reflector, on the contrary, reduces shading of the opening, but it must be located away from the main one. Advantages compared to a parabolic antenna: compactness (despite the presence of a second reflector, the total distance between the two reflectors is less than the distance from the feed to the reflector of a parabolic antenna), reduced losses (the receiver can be placed close to the horn emitter), reduced side lobe interference for ground radars. Main disadvantages: the beam is blocked more strongly (the size of the auxiliary reflector and feed is larger than the size of the feed of a conventional parabolic antenna), does not work well with a wide range of waves.
Radiation scheme
Antenna Gregory
On the left is the Gregory antenna, on the right is the Cassegrain antenna
The Gregory parabolic antenna is very similar in structure to the Cassegrain antenna. The difference is that the auxiliary reflector is curved in the opposite direction. Gregory's design can use a smaller secondary reflector compared to a Cassegrain antenna, resulting in less of the beam being blocked.
Offset (asymmetric) antenna
As the name suggests, the emitter and auxiliary reflector (if it is a Gregory antenna) of an offset antenna are offset from the center of the main reflector so as not to block the beam. This design is often used on parabolic and Gregory antennas to increase efficiency.
Cassegrain antenna with flat phase plate
Another design designed to combat beam blocking by an auxiliary reflector is the flat plate Cassegrain antenna. It works taking into account the polarization of waves. An electromagnetic wave has 2 components, magnetic and electric, which are always perpendicular to each other and the direction of movement. Wave polarization is determined by orientation electric field, it can be linear (vertical/horizontal) or circular (circular or elliptical, twisted clockwise or counterclockwise). The interesting thing about polarization is the polarizer, or the process of filtering the waves, leaving only waves polarized in one direction or plane. Typically, the polarizer is made of a material with a parallel arrangement of atoms, or it can be a lattice of parallel wires, the distance between which is less than the wavelength. It is often assumed that the distance should be approximately half the wavelength.
A common misconception is that the electromagnetic wave and polarizer work in a similar way to an oscillating cable and a plank fence - that is, for example, a horizontally polarized wave must be blocked by a screen with vertical slits.
In fact, electromagnetic waves behave differently than mechanical waves. A lattice of parallel horizontal wires completely blocks and reflects a horizontally polarized radio wave and transmits a vertically polarized one - and vice versa. The reason is this: when an electric field, or wave, is parallel to a wire, it excites electrons along the length of the wire, and since the length of the wire is many times greater than its thickness, the electrons can easily move and absorb most of the energy of the wave. The movement of electrons will lead to the appearance of a current, and the current will create its own waves. These waves will cancel out the transmission waves and behave like reflected waves. On the other hand, when the electric field of the wave is perpendicular to the wires, it will excite electrons across the width of the wire. Since the electrons will not be able to actively move in this way, very little energy will be reflected.
It is important to note that although in most illustrations radio waves have only 1 magnetic field and 1 electric field, this does not mean that they oscillate strictly in the same plane. In fact, one can imagine that electric and magnetic fields consist of several subfields that add up vectorially. For example, for a vertically polarized wave from two subfields, the result of adding their vectors is vertical. When two subfields are in phase, the resulting electric field will always be stationary in the same plane. But if one of the subfields is slower than the other, then the resulting field will begin to rotate around the direction the wave is moving (this is often called elliptical polarization). If one subfield is slower than the others by exactly a quarter of a wavelength (the phase differs by 90 degrees), then we get circular polarization:
To convert linear polarization of a wave into circular polarization and back, it is necessary to slow down one of the subfields relative to the others by exactly a quarter of the wavelength. For this, a grating (quarter-wave phase plate) of parallel wires with a distance between them of 1/4 wavelength, located at an angle of 45 degrees to the horizontal, is most often used.
For a wave passing through the device, linear polarization turns into circular, and circular into linear.
A Cassegrain antenna with a flat phase plate operating on this principle consists of two reflectors of equal size. The auxiliary reflects only horizontally polarized waves and transmits vertically polarized waves. The main one reflects all waves. The auxiliary reflector plate is located in front of the main one. It consists of two parts - a plate with slits running at an angle of 45°, and a plate with horizontal slits less than 1/4 wavelength wide.
Let's say the feed transmits a wave with circular polarization counterclockwise. The wave passes through the quarter-wave plate and becomes a horizontally polarized wave. It is reflected from horizontal wires. It again passes through the quarter-wave plate, on the other side, and for it the plate wires are already oriented mirror-image, that is, as if rotated by 90°. The previous change in polarization is reversed, so that the wave again becomes circularly polarized counterclockwise and travels back to the main reflector. The reflector changes polarization from counterclockwise to clockwise. It passes through the horizontal slits of the auxiliary reflector without resistance and leaves in the direction of the targets, vertically polarized. In receive mode, the opposite happens.
Slot antenna
Although the described antennas have fairly high gain relative to the aperture size, they all have common disadvantages: high side-lobe susceptibility (susceptibility to clutter reflections from the ground and sensitivity to targets with a low effective scattering area), reduced efficiency due to beam blocking (small radars that can be used on aircraft have a problem with blocking; large radars, which have less of a problem with blocking, cannot be used in the air). As a result, a new antenna design was invented - a slot antenna. It is made in the form of a metal surface, usually flat, in which holes or slots are cut. When it is irradiated at the desired frequency, electromagnetic waves are emitted from each slot - that is, the slots act as individual antennas and form an array. Since the beam coming from each slot is weak, their side lobes are also very small. Slot antennas are characterized by high gain, small side lobes and low weight. They may lack protruding parts, which in some cases is their important advantage(for example, when installed on aircraft).
Radiation scheme
Passive phased array antenna (PFAR)
Radar with MIG-31
Since the early days of radar development, developers have been plagued by one problem: the balance between accuracy, range and scan time of the radar. It arises because radars with a narrower beam width increase accuracy (increased resolution) and range at the same power (power concentration). But the smaller the beam width, the longer the radar scans the entire field of view. Moreover, a high-gain radar will require larger antennas, which is inconvenient for fast scanning. To achieve practical accuracy on low frequencies the radar would require antennas so huge that they would be mechanically difficult to rotate. To solve this problem, a passive phased array antenna was created. It relies not on mechanics, but on the interference of waves to control the beam. If two or more waves of the same type oscillate and meet at one point in space, the total amplitude of the waves adds up in much the same way as waves on water add up. Depending on the phases of these waves, interference can strengthen or weaken them.
The beam can be shaped and controlled electronically by controlling the phase difference of a group of transmitting elements - thus controlling where amplification or attenuation interference occurs. It follows from this that the aircraft radar must have at least two transmitting elements to control the beam from side to side.
Typically, a radar with PFAR consists of 1 feed, one low-interference amplifier, one power distributor, 1000-2000 transmitting elements and an equal number of phase shifters.
Transmitting elements can be isotropic or directional antennas. Some typical types of transmission elements:
On the first generations of fighter aircraft, patch antennas (strip antennas) were most often used because they were the easiest to develop.
Modern active phase arrays use groove emitters due to their wideband capabilities and improved gain:
Regardless of the type of antenna used, increasing the number of radiating elements improves the radar's directivity characteristics.
As we know, for the same radar frequency, increasing the aperture leads to a decrease in beam width, which increases range and accuracy. But for phased arrays, it is not worth increasing the distance between the emitting elements in an attempt to increase the aperture and reduce the cost of the radar. Because if the distance between the elements is greater than the operating frequency, side lobes may appear, significantly degrading the radar's performance.
The most important and expensive part of the PFAR is the phase shifters. Without them, it is impossible to control the signal phase and beam direction.
They happen different types, but in general they can be divided into four types.
Phase shifters with time delay
The simplest type of phase shifters. It takes time for a signal to travel through a transmission line. This delay, equal to the phase shift of the signal, depends on the length of the transmission line, the frequency of the signal, and the phase velocity of the signal in the transmitting material. By switching a signal between two or more transmission lines of a given length, the phase shift can be controlled. Switching elements are mechanical relays, pin diodes, field effect transistors or microelectromechanical systems. Pin diodes are often used because of their high speed, low loss, and simple bias circuits that provide resistance changes from 10 kΩ to 1 Ω.
Delay, sec = phase shift ° / (360 * frequency, Hz)
Their disadvantage is that the phase error increases with increasing frequency and increases in size with decreasing frequency. Also, the phase change varies with frequency, so they are not applicable for very low and high frequencies.
Reflective/quadrature phase shifter
Typically this is a quadrature coupling device that splits the input signal into two signals 90° out of phase, which are then reflected. They are then combined in phase at the output. This circuit works because signal reflections from conductive lines can be out of phase with respect to the incident signal. The phase shift varies from 0° (open circuit, zero varactor capacitance) to -180° (shorted circuit, infinite varactor capacitance). Such phase shifters have a wide operating range. However, the physical limitations of varactors mean that in practice the phase shift can only reach 160°. But for a larger shift it is possible to combine several such chains.
Vector IQ modulator
Just like a reflex phase shifter, here the signal is split into two outputs with a 90-degree phase shift. The unbiased input phase is called the I-channel, and the quadrature with a 90-degree offset is called the Q-channel. Each signal is then passed through a biphasic modulator capable of shifting the phase of the signal. Each signal is phase shifted by 0° or 180°, allowing any pair of quadrature vectors to be selected. The two signals are then recombined. Since the attenuation of both signals can be controlled, not only the phase but also the amplitude of the output signal is controlled.
Phase shifter on high/low pass filters
It was manufactured to solve the problem of time-delay phase shifters not being able to operate over a large frequency range. It works by switching the signal path between high-pass and low-pass filters. Similar to a time delay phase shifter, but uses filters instead of transmission lines. Filter treble consists of a sequence of inductors and capacitors that provide phase advance. Such a phase shifter provides a constant phase shift in the operating frequency range. It is also much smaller in size than the previous phase shifters listed, which is why it is most often used in radar applications.
To summarize, compared to a conventional reflective antenna, the main advantages of PFAR will be: high speed scanning (increasing the number of targets tracked, reducing the likelihood of the station detecting an radiation warning), optimization of time on target, high gain and small side lobes (harder to jam and detect), random scan sequence (harder to jam), ability to use special modulation and detection techniques to extract signal from noise. The main disadvantages are high cost, the inability to scan wider than 60 degrees in width (the field of view of a stationary phase array is 120 degrees, a mechanical radar can expand it to 360).
Active phased array antenna
Outside, AFAR (AESA) and PFAR (PESA) are difficult to distinguish, but inside they are radically different. PFAR uses one or two high-power amplifiers that transmit a single signal, which is then divided into thousands of paths for thousands of phase shifters and elements. An AFAR radar consists of thousands of reception/transmission modules. Since the transmitters are located directly in the elements themselves, it does not have a separate receiver and transmitter. The differences in architecture are shown in the picture.
In AFAR, most of the components, such as a weak signal amplifier, a high power amplifier, a duplexer, and a phase shifter, are reduced in size and assembled in one housing called a transmit/receive module. Each of the modules is a small radar. Their architecture is as follows:
Although AESA and PESA use wave interference to shape and deflect the beam, the unique design of AESA provides many advantages over PFAR. For example, an amplifier weak signal is located close to the receiver, up to the components where part of the signal is lost, so it has a better signal-to-interference ratio than PFAR.
Moreover, with equal detection capabilities, AFAR has a lower duty cycle and peak power. Also, since individual modules AFARs do not rely on a single amplifier; they can simultaneously transmit signals at different frequencies. As a result, AFAR can create several separate beams, dividing the array into subarrays. The ability to operate on multiple frequencies brings multitasking and the ability to deploy electronic jamming systems anywhere in relation to the radar. But forming too many simultaneous beams reduces the radar's range.
The two main disadvantages of AFAR are high cost and limited field of view to 60 degrees.
Hybrid electronic-mechanical phased array antennas
The very high scanning speed of the phased array is combined with a limited field of view. To solve this problem, modern radars place phased arrays on a movable disk, which increases the field of view. Do not confuse the field of view with the width of the beam. Beam width refers to the radar beam, and field of view refers to the overall size of the space being scanned. Narrow beams are often needed to improve accuracy and range, but a narrow field of view is usually not necessary.
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The utility model relates to the technology of microwave antennas and can be used in radio-electronic systems as an active phased array antenna, in particular, in airborne and shipborne locators and radio countermeasures systems.
The technical result is to increase the reliability of beam control through the use of a plasma reflector.
The essence of the utility model is that the antenna is made in the form of a Helmholtz coil consisting of a vacuum chamber, an irradiator, a linear cathode and an anode, while a layer of plasma is applied to the coil from which the signal is reflected. Ill.1.
The utility model relates to the technology of microwave antennas and can be used in radio-electronic systems as an active phased array antenna, in particular, in airborne and shipborne locators and radio countermeasures systems.
Among the latest developments in the field of creating phased arrays, carried out in the EU countries, is a multifunctional radar with phased arrays, designed for installation on a ship. The radar on the TWT transmitter operates in the C-band wavelengths. The target detection range reaches 180 km. The antenna array rotates in azimuth at speed. 60 rpm Phase control of the beam is performed in the elevation plane.
A spatial transceiver phased antenna array is known. Patent 2287876 Russia, MPK H01Q 3/36, 2006. The array is made in the form of a matrix and contains a master mixer, to which the signals of the master frequencies f and f are supplied, the output signals of the service frequencies f 1 =f and f 2 =f-f through the corresponding phase shifters are supplied respectively to the rows and columns of the matrix; at the intersection points of the rows and columns of the matrix, mixers are located, the output of each of which is connected to the corresponding circulator connected through the corresponding receiving amplifier.
A passive-active phased array antenna for the microwave range is also known. RF patent 2299502, 2006 (prototype). The array consists of n radiating elements, n transmit-receiver modules (RTM) and a distribution system, while the RPM includes m active RPMs, each of which contains a power amplifier of the transmitting channel, low-noise amplifiers of the receiving channel, phase shifters and a control and monitoring circuit, and ( n-m) passive PPMs, each of which contains a phase shifter and a phase shifter control circuit.
The disadvantages of both the analogue and the prototype are the low reliability of the beam control system, large dimensions, as well as low accuracy and speed of beam installation.
The purpose of the utility model is to improve the reliability of beam control through the use of a plasma reflector.
This goal is achieved by the fact that the phased antenna array of the microwave range, containing emitting and transmitting elements, power amplifiers of the transmitting and receiving channels, as well as a phase shifter control circuit, is made in the form of a Helmholtz coil consisting of a vacuum chamber, an irradiator, a linear cathode and an anode, with In this case, a layer of plasma is applied to the coil from which the electron scanning beam is reflected, and the plasma layer is created in a vacuum chamber during a gas discharge between the anode plate and the linear cathode, which is a line of elements of a certain address on the two-coordinate grid of the cathode.
In FIG. Shown functional diagram antennas with electronic beam scanning.
It contains:
1 - vacuum chamber;
2 - plasma layer;
3 - irradiator;
4 - Helmholtz coil;
5 - linear cathode;
6 - reflected signal;
In such an antenna, electronic control of the beams is carried out using a plasma reflector.
Plasma with sufficient density has the ability to reflect electromagnetic energy. Moreover, the higher the irradiation frequency, the greater the density of the plasma.
Plasma layer 2 is created in vacuum chamber 1 during a gas discharge between the anode plate 7 and the linear cathode 5, which is a line of elements of a certain address on the two-coordinate grid of the cathode. By changing the position of the linear cathode 5, it is possible to rotate the plasma layer 2 and thereby scan the reflected beam 6 in azimuth. Scanning the beam by elevation angle is carried out by changing the inclination of the plasma reflector by adjusting magnetic field Helmholtz coils. The latter are placed around the reflector so as not to block the microwave signal. The position of the linear cathode 5 and the value of magnetic induction are controlled by a control system (computer).
According to calculations, the accuracy of beam installation in a given direction is 1-2°. The beam reorientation time is about 10 μs.
To form plasma layer 2 in chamber 1, it is sufficient to maintain a vacuum of approximately 15 Pa. The magnetic induction should be about 0.02 Tesla, the current should be about 2 A and the voltage should be 20 kV. The size of the reflector is about 50×50×1 cm. The level of the side lobes is 20 dB.
Among the advantages of the proposed antenna is the ability to quickly and accurately install the beam, which allows you to simultaneously perform search and tracking operations for a group of targets, as well as form different radiation patterns. In addition, such an antenna has a wide frequency band, as a result of which the same plasma reflector can be used with different feeds. The range of the proposed antenna is from 5 to 50 GHz. Unlike conventional reflective antennas, which significantly increase the effective scattering area of the locator when irradiated by radio reconnaissance means of a potential enemy, this parameter in a plasma antenna is small. Thermal radiation from the antenna is also small, since thermal energy is concentrated inside the plasma and is not radiated outward.
A phased array antenna of the microwave range containing emitting and transmitting elements, power amplifiers of the transmitting and receiving channels, as well as a phase shifter control circuit, characterized in that the antenna is made in the form of a Helmholtz coil, consisting of a vacuum chamber, an irradiator, a linear cathode and an anode, with In this case, a layer of plasma is applied to the coil, from which the electron scanning beam is reflected, and the plasma layer is created in a vacuum chamber during a gas discharge between the anode plate and the linear cathode, which is a line of elements of a certain address on the two-coordinate grid of the cathode.
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A microwave signal power amplifier belongs to the field of electrical engineering and is used to increase the range of information transmission and improve the operation of radio equipment of an unmanned aerial vehicle (UAV). Distinctive feature devices is the ability, when transmitting information, to reduce phase and amplitude dispersion, to maintain stable technical specifications in the microwave range.
