RU2711115C1 - Radar method of detecting low-visibility targets in pulse-doppler radar station with paa - Google Patents

Abstract

FIELD: radar ranging and radio navigation.SUBSTANCE: invention relates to methods for radar detection of low-visibility targets and can be used to obtain a multi-beam mode in a standard pulse-Doppler radar station (RS) with a passive phased antenna array (PAA) or for additional multiple increase in the number of beams in a multibeam radar station with an active PAA. Technical result is achieved due to that transmitting and PAA beam control system transmitting probing pulses, and by means of single-channel, series-connected receiver, analogue-to-digital converter, echo signal converter to video frequency, optimum filter, echo signal distributor by separate channels and moving target selection system, moving objects are detected, as well as due to the fact that the directions of the transmitted and received beams of the phased antenna array are changed, the echo signals are distributed at the video frequency both on the beam channels and in the range channels in each of the beam channels and detection of moving targets by a selection system having a number of channels equal to the product of the number of beams per number of range channels over a certain period of pulses of the transmitter.EFFECT: improved efficiency of pulse-Doppler radar station with PAA when operating on low-visibility and low-speed objects.1 cl, 6 dwg, 1 tbl

Description

The invention relates to methods for radar detection of inconspicuous targets, including UAVs, MLRS missiles, as well as ground and surface targets. Advantageously, the method can be used to obtain a special multipath mode in a typical pulse-Doppler radar with a passive headlamp, or for an additional multiple increase in the number of beams in a multipath radar with an active headlamp.

A known method of radar detection of inconspicuous targets [1], using the region of resonant scattering of an electromagnetic wave incident on the object, in which the product (2π / λ) ⋅L≈1 takes place, where L is the size of the object or its characteristic part, while the ESR of the object can increase strongly relative to the EPR of this object in the reflection zone, usually used in pulse-Doppler radar, on which (2π / λ) ⋅L >> 1. To get into the resonance region in each direction of space, a search is carried out by the carrier frequency of the emitted radio pulses of the packets until the maximum of the echo signal from the target is detected.

The disadvantage of this method is the large required range of the selected carrier frequencies (from 150 MHz to 6 GHz in 10 MHz steps), for the implementation of which conventional pulse-Doppler radars cannot be used, in which the frequency tuning can be no more than ± 15-20 % In addition, this method, when searching by frequency, requires the emission of a large number of bursts, which will slow down the survey of space.

There is a method of observing an inconspicuous low-speed UAV in the field of urban development using ultra-short pulsed radar technology [2]. The advantage of this technology is a high range resolution due to a short radio pulse (duration 10 ns or less), a minimum of side lobes in range, due to the use of a simple signal, and the ability to select a moving target by means of interframe processing, without using the Doppler effect, therefore without the presence of "blind" speeds.

However, due to the inherent high duty cycle of the probe pulses (about 10 ⁴ ), this method is difficult to use for detecting small targets at a range of about 10-15 km, along with other, faster targets, which is required in military complexes. For the same reason, this method cannot be implemented as a mode in modern solid-state pulsed-Doppler radars operating at wells of the order of 10 ... 40.

Known is a method of increasing the accumulation time (time burst T _Pace) preserving tempo viewing space in a pulse-Doppler radar with passive phased array through expansion of beam antennas to transmit and receive [3].

раз уменьшается дальности обнаружения РЛС, что следует из основного уравнения радиолокации.The disadvantage of this method is that when the solid angle of the BOTTOM is expanded at a level of 3 dB by n _ϕ times, the radar's solid resolution deteriorates by the same amount, as well as

times decreases the radar detection range, which follows from the basic equation of radar.

Known multi-beam detection method in a pulse-Doppler radar with a semi-active or active headlamp with digital beamforming [4.]. According to this method, an extended beam is formed for transmission using a transmitting antenna or headlamp, within which several narrow receiving beams are formed using an active receiving headlamp, multichannel radar receiver and digital beamforming device, which are processed separately by the typical pulse-Doppler radar method. In such radars, due to the parallel processing of N _L. rays, the accumulation time of target signals increases by the same amount while maintaining the rate of view, the range of detection of the target and the angular resolution of the target.

The disadvantages of this method are as follows:

- the method cannot be implemented in radars with passive headlights, which make up the majority of modern radars with headlights, including air defense systems;

- Radars with active or semi-active headlamps with digital beamforming are much more complicated and expensive than radars with passive headlamps;

- the directions of the receiving beams in a multipath radar with an active or semi-active phased array cannot be arbitrary. They should be located only within the extended transmitted beam;

- in multi-beam radars with active or semi-active headlamps, an ambiguous range measurement takes place, which requires additional transmissions with a different pulse period to confirm the detection of stealth targets located in the near range;

- the number of N _L rays in a radar with an active or semi-active PAR is limited by its hardware structure and the possible value of the processed data stream.

Closest to the proposed invention is a typical single-beam method of pulse-Doppler radar detection in radars with passive headlamps [5, p. 186], which is a prototype.

In FIG. 1 shows the structure of a pulse-Doppler radar with a passive headlamp, in which the dotted line corresponds to a typical single-beam pulse-Doppler detection method, taken as a prototype.

In FIG. 1 is indicated: 1 - shift register with bit depth M _f ; 2 - parallel register bit M _f ; 3 - M discrete phase shifter digit _F, the total number of phase shifters corresponding to the number of emitters N = N _{and p;} 4 - beam control system (SUL); 5 - power distributor; 6 - antenna switch; 7 - transmitter; 8 - single-channel radar receiver; 9 - analog-to-digital Converter (ADC); 10 - frequency converter with intermediate to video frequency and optimal (matched) filter for receiving a useful signal; 11 - RAM and sample allocator; 12 - calculators fast Fourier transform (FFT); 13 - threshold detectors; 14 - synchronizer; 15 - Central computing system (CVS). Elements 12 and 13 form a system of selection of moving targets (SDS). C1 - a clock pulse in the shift registers of the phase shifters; C2 - clock rewrite the phases into a parallel register of phase shifters; C3 - trigger pulse of the probe pulse of the transmitter; C4 - pulse clock receiver; C5 - ADC clock pulses; C6 - pulses of the transponder clock; C7 - pulses of the beginning of the pack.

In FIG. 2 shows timing diagrams of a typical implementation of a method taken as a prototype.

The single-beam method of pulse-Doppler radar detection in a radar with a passive phased array, taken as a prototype, is implemented as follows.

Before the beginning of each nth burst, the CVS sets the single direction of the beam α [n] = {elevation angle, azimuth} in the LMS in the LMS. In the LMS according to the dependences [5, C. 613], the phases are calculated for all N _f phase shifters ϕ _i (α [n]), where i = 1, 2 ... N _f , which are recorded in the shift register of each i-th phase shifter and clock the beginning of the packet C2 is rewritten in a parallel register of these phase shifters and fed to the inputs of the phase shifters themselves. Throughout the nth pack, the phase shifter phase codes remain unchanged. Therefore, during the burst, all probe pulses are sent in one direction and all echo signals are received from the same direction. Correspondingly, in the distributor 11, all samples of the signal signals on the video frequency are separated by N _R range channels, in each of which FFT is produced in block 12, and threshold detection of the target is carried out in block 14.

The main disadvantage of the single-beam detection method, taken as a prototype, when applied to low-speed, low-speed UAV-type targets, is the difficulty in resolving two conflicting requirements. The first requirement: to enable the selection of a low-speed target against the background of passive interference from the ground and weather patterns, as well as to improve the resolution of targets by speed, a longer duration of a pack of coherent pulses is required. The second requirement: due to the great maneuverability of UAV-type targets, a high speed of viewing the space is needed.

In addition, when using the single-beam pulsed-Doppler detection method, there is an influence of interference arising from the reflection of signals from areas and targets located beyond the limits of unambiguous range determination, including possible interference due to the phenomenon of super-refraction characteristic of the review of the surface situation. As a result, the measurement of the range in one burst is ambiguous, and additional confirmations with a different pulse period are required to confirm the detection of stealth targets in the near range.

The single-beam pulse-Doppler method, taken as a prototype, especially when used in modern radars having a solid-state transmitter with a low duty cycle, has one more drawback. It lies in the difficulty of resolving two conflicting requirements. The first requirement: to ensure a long range of detection of inconspicuous targets with good resolution in range, it is required to use a complex probing signal with a long duration. The second requirement: due to the great maneuverability of UAV-type targets, it is necessary to ensure a small minimum detection range, which is only possible with a simple probe pulse having a short duration.

The technical result of the invention is to improve the efficiency of a pulse-Doppler radar with a phased array when working on stealth and low-speed objects. To achieve this, the following basic objective of the invention is set - the development of a method that allows to impart to the well-known single-beam method of operating a pulse-Doppler radar with a passive phased array, taken as a prototype, of a new property - the property of receiving multiple rays during a burst. The solution to this basic problem also allows in a typical multi-beam radar with AFAR, taken as an analog, to multiply the number of rays without increasing the total flow of processed data of the echo signals.

Specifically, in the known radar method for detecting inconspicuous targets in a pulse-Doppler radar with a PAR, in which, using a transmitter and a beam control system, PAR, transmit probing pulses, and using a single-channel, serially connected receiver, an analog-to-digital converter, an echo signal converter to the video frequency, the optimal filter, the distributor of the echo samples on individual channels and the moving target selection system detect moving targets, I distinguish Take into account the fact that using the PAR control beam system during a burst of probe pulses before each probe pulse with a cycle equal to the number of beams generated during the burst, change the direction of the transmitted and received PA beams, distribute the samples of the echo signals at the video frequency to distribute the samples as channels rays, in accordance with the direction of the rays in a given period of probing pulses, and along the range channels in each of the ray channels, by a moving target selection system having the number of channels equal to the dividing the number of rays by the number of range channels, moving targets are detected and the pulse period of the transmitter is set, corresponding to the instrumental range of the radar.

In addition, with one direction of the transmitting and receiving beams, the probe pulse is divided into two probe pulses, the first of which is a simple, short duration corresponding to a given minimum target range and the required range resolution, the second pulse is a complex, long duration corresponding to a given maximum detection range the target and the required resolution in range, set the interval between the probe pulses greater than or equal to the duration of the second pulse, while receiving int vomited between probing pulses produce optimum processing for the first pulse of the echo signal, and in the interval after the second pulse to produce an optimal second pulse until the end of processing the echo signal, and processing results detected moving target.

By solving this basic problem, the work of the radar on low-visibility low-speed targets will be free from the above disadvantages of the prototype and analogues. The solution of the basic problem will allow to obtain the following positive technical results that make the proposed method effective:

1) the possibility of increasing the coherent accumulation time of the signal from the target (burst time) required for selecting low-speed targets against the background of passive interference, while maintaining the target detection range and the speed of the space survey;

2) the ability to improve the resolution of targets by speed (the ability to obtain a “speed magnifier”) required for selecting targets in a group, recognizing the type of targets and other tasks, while maintaining the range of detection of targets and the speed of viewing space;

3) the ability to quickly increase the speed of the review of space while maintaining the duration of the pack. This feature allows you to increase the range of the target load that the radar can withstand;

4) the ability to unambiguously measure the target range from one burst and virtually eliminate the influence of interference arising from the reflection of signals from surface areas located beyond the limits of unambiguous range determination, including interference due to the phenomenon of super-refraction characteristic of a surface survey (the so-called interference at the nth scan progress [6]);

5) the possibility in one period of radiation to combine work with a probing signal that is optimal to ensure that the specified requirements for a minimum detection range and resolution of targets, and work with another probing signal that is optimal to provide specified requirements for a maximum detection range and resolution of targets.

The invention is illustrated using schemes where:

- in FIG. 1 shows the structure of a pulse-Doppler radar with a passive headlamp, in which the inventive multi-path method is implemented. The part of the structure indicated by the dotted line corresponds to a typical single-beam pulse-Doppler method with a passive phased array taken as a prototype;

- in FIG. 2 is a timing chart of a typical implementation of a method taken as a prototype;

- in FIG. 3 - timing diagrams of the implementation of the inventive multi-beam method for detecting stealth targets;

- in FIG. 4 - time diagrams of the implementation of the requirements of combining in one pack of small minimum range and large maximum range of detection of inconspicuous targets using the inventive multi-beam method;

- in FIG. 5 - amplitude-frequency characteristics of the SDC filters when using the single-beam detection method, taken as a prototype, and when using the inventive multi-beam method, as well as the energy spectra of passive interference of the terrain in the wind having a different speed;

- in FIG. 6 shows the results of optimal processing of echoes from a target when probing pulses are shown in FIG. 4.

Differences from the prototype when working on the alleged burst multipath method are as follows:

- before the beginning of each n-th packet from the DAC 15 transmit to the SUL 4 task is not in one direction of the beam, as in the prototype in FIG. 2, and for all N _l directions of this multipath burst α _j [n] where j = 1, 2 ... N _l . Accordingly, before the start of each nth burst in the SUL 4, the phases ϕ _i (α _j [n] are calculated and stored for all N _f phase shifters for all N _l beam directions, where i = 1, 2 ... N _f , j = 1, 2 ... N _l

- during the burst, using SUL 4 from pulse to pulse, the direction of the probe and received beam is changed in the following cyclic order α ₁ , α ₂ , ... α _Nl , α ₁ , α ₂ , ... α _Nl , ... α ₁ , α ₂ , ... α _Nl In this setting at the next period of the transmitter pulses of the desired beam direction α _j [n] is performed by recording in the previous period in the registers of all N _f shifters calculated phase _{φ i (α j [n]} , where i = 1, 2, ... N _p, and the installation of these phases in the phase shifters before the probing pulse of a given period.

- when processing the received echoes, the distributor 11 distributes the signal samples not only on the N _R range channels, as in the prototype, but also on the N _l channel directions of the rays;

число каналов N_СДЦ=Nл*N_R, чем число каналов системы СДЦ прототипа N_СДЦ.П=N_R. При этом каждый канал СДЦ такой же, как в прототипе (состоит из вычислителя БПФ 12 и порогового обнаружителя 13). В результате в одной пачке производят обнаружение целей на однозначной дальности по N_л лучам, имеющим разное направление, вместо одного луча, как в прототипе.- selection of moving targets is carried out by the SDS system having

the number of channels N _SDC = Nl * N _R than the number of channels of the SDC system of the prototype N SDC. _P = N _R. Moreover, each channel SDS is the same as in the prototype (consists of an FFT calculator 12 and a threshold detector 13). As a result, in one pack, targets are detected at an unambiguous range in N _l rays having a different direction, instead of a single beam, as in the prototype.

Thus, in the passive phased array, the work according to the proposed method is organized due to the fast switching of the beam direction α _i carried out with the help of the SUL 4 before each probe pulse during the burst. In this case, during the beam direction α _i from pulse to pulse, α ₁ , α ₂ , ... α _Nl , α ₁ , α ₂ , ... α _Nl , ... α ₁ , α ₂ ... α _{Nl are} established in the following cyclic order. Therefore, in contrast to the well-known multipath method of the active PAR, taken above as an analogue, in which each echo signal is received by an antenna with a multipath BOTTOM, according to the proposed method, the multipath mode is burst because it is formed elementwise during the entire packet of probing pulses.

In the proposed burst multipath mode, each direction α _i , determined by its azimuth and elevation angle, can be arbitrary. The transmitter 7 runs in normal mode, for generating burst duration T _{Pace. n} at the carrier frequency simple or complex probe pulses with the required intrapulse modulation, pulse duration t _and , pulse period T _and . _p , duty cycle Q _p = T _and . _p / t _and and the number of pulses N _p = T _pach.p / T _and . _n .

Echo signals are received during the burst, as in a typical single-beam mode of a pulse-Doppler radar [4, p. 186], using a single-channel receiver 8, ADC 9 and optimal (matched to the useful signal) compression filters 10. Then, by the distributor 11 the time samples of the processed echo signals are separated by the channels of the directions of the rays α ₁ , α ₂ , ... α _Nl and separately for each direction of the received beam along the distance channels. Further, for each direction of the beam, in each range channel, similarly as in the typical single-beam mode, spectral analysis of signals is performed in the FFT calculator 12 and in the threshold detector 13 detection of targets against the background of interference. Echo reception during the burst is also illustrated in the timing diagram of FIG. 3.

It follows that in the proposed burst multipath mode after the radiation of the next probe pulse in its direction, the receiving beam will be directed only during the time of one period of the transmitter pulses (in the terminology of [5] of the 1st “sweep”), after which the receiving beam changes direction and restores the direction that coincides with the direction of the probe beam only in the (Nl + 1) -th “sweep”. Therefore, echo signals from a given direction only from the range interval ΔR = c * T _i.p / 2 corresponding to its unambiguous measurement get into the receiver without suppression. Signals coming from the same direction, from an interval of the same length ΔR, but located at a much greater distance equal to (Nl * ΔR), will also have a large suppression proportional to the fourth power of the range, which virtually eliminates their influence .. Possible echo signals coming from other (previous) directions of this pack will be significantly weakened, because enter the entrance through the side lobes of the bottom and from a distance greater than ΔR. This explains the achievement of the fourth of the above technical results of the invention.

The achievement of the fifth of the above technical results of the invention is also a consequence of the fact that practically only the range interval corresponding to its unambiguous measurement gets into the receiver. If it is required to combine the given requirements of a small minimum and a large maximum detection range of an inconspicuous target such as a UAV and others in one packet, then when using the proposed method for one period of probe pulses in the same direction of the transmitting and receiving beam, as explained in FIG. 4, the probe pulse is divided into two pulses: the first pulse is simple, short in duration t1 _and corresponding to the specified minimum target detection range and range resolution, and the second pulse is complex, long in duration t2 _and corresponding to the required maximum target detection range and resolution in range. The interval between pulses should be τ1≥t2 _u . At reception in the interval t1 _{and the} signal block in the range of τ1 between pulses produce optimum for the first pulse (compatible with the first pulse) filtering the interval t2 _{and the} signal is blocked and the interval τ2 produce optimal for the second pulse (agreed with the second pulse) filtering . With this processing, the echo signals from the first pulse can practically be detected only on the interval τ1, where they are processed with their own matched filter. In this case, the echo signals from the second pulse practically do not affect, because they come from a very long range corresponding to a delay T _i.p * N _l , where N _l is the number of rays and are suppressed by a compression filter that is not consistent with them.

Echo signals from the second pulse can be detected only in the interval τ2, where they are processed with their own matched filter, because on this interval, the signals from the first pulse are small in power and are suppressed by a compression filter that is not consistent with them.

According to the above, in the proposed burst multipath method from each direction α _j (j = 1, 2 ... Nl), a packet of echo signals with the parameters specified in Table 1 is received at the reception. 1. The same table, for comparison, shows the parameters of the echo signals in the equivalent pace of review N _l single-beam packets having the same directions α1, α2, ... α _Nl , but a shorter duration equal to T _pack = T _pack . _p / Nl. Such packs occur when using the method taken as a prototype.

According to the table. 1 as well as FIG. 2 and FIG. 3, it is possible to compare the proposed burst multipath method with equivalent single-beam bundles of the prototype equivalent in sounding speed Nl according to the following main indicators [5].

1) When using the method proposed burst multipath coherent accumulation time of the signal from the target (T _Pace burst duration) in N _l times greater than the equivalent single beam for sensing the speed packs prototype. This is the main advantage of the proposed multipath method.

2) When using the proposed burst multipath method, a speed resolution equal to δV = λ / (2T _pack ), where λ is the radar wavelength is N _l times better (δV less) than in the single-beam prototype packets equivalent in sounding speed.

3) When using the proposed burst multipath method, the detection range equal to R = m⋅ ( _Tpach / Q) ^1/4 , where m is the proportionality coefficient, is the same as in the single-beam prototype packets equivalent in speed of view.

4) The period of ambiguity in speed, equal to ΔV = λ / (2T _and ), when using the proposed burst multipath method, is N _l times less than in equivalent single-beam bundles of the prototype. For low-speed targets such as UAVs, this drawback is not significant, because their speed is still measured unambiguously. For faster goals, this drawback is also not fundamental, because for them, the resolution of the ambiguity in speed in the multipath mode can be carried out according to the well-known method [5], using the premise of ties with a different pulse period.

5) When using the proposed burst multipath method, interference from targets located outside the unique range can come only from the “(Nl + 1) -th sweep stroke.”, And in equivalent single-beam bursts already starting from the second “sweep stroke”. Correspondingly, the suppression of such interference in the burst multipath mode will be at least (N _l ⁴ ) times greater than the equivalent one-beam bursts with the same scanning speed, and their effect will practically not be affected.

6) When using the proposed burst multipath method, the range ΔR = c * T _i.p / 2 is equal to the maximum possible (instrumental) range of the radar, and in equivalent single-beam bursts, the range ΔR is equal to the period of ambiguity in range and the instrumental range may to be bigger. For subtle purposes for which the invention is intended, this drawback is not significant since their detection range is still less than the ΔR range. On the other hand, the fundamental limitation of the range by one period of ambiguity can in many cases be considered as a unique advantage of the burst multipath method, which makes it possible to unambiguously measure the target range by one burst in this mode and practically eliminate interference arising from the reflection of signals from surface areas located outside the unique determination of range, including interference due to the phenomenon of super-refraction, characteristic of surface targets.

7) All N _p directions of reviews in one bundle with the proposed burst multipath method can be any, as in equivalent single-beam bundles. However, this property does not possess, taken as an analogue, a multi-beam radar with an active PAR.

раз меньше, чем в равной ей по длительности однолучевой, что должно быть учтено в алгоритме управления. Например, при N_л=2 в 2 раза увеличится скорость обзора пространства, но при этом на 19% уменьшится дальность обнаружения и инструментальная дальность будет соответствовать только одному периоду импульсов передатчика Т_и.п.On the other hand, by using the proposed method multipath burst can be increased N times _l viewing space velocity during preservation burst duration, ie the third made from the above results. In the event of a large flow of targets and false objects requiring additional rays for tying and auto tracking of targets, transitions to a multipath package will save the total viewing cycle time of a given space. The bursts with the proposed multi-beam method and equal in duration single-beam bursts have the same speed resolution and can be conveyed by any alternation. However, in this case, the detection range of targets in a multipath packet in

times less than in equal one-beam durations, which should be taken into account in the control algorithm. For example, when N _l = 2, the speed of the survey of space will increase by 2 times, but at the same time, the detection range will decrease and the instrumental range will correspond to only one period of the transmitter pulses T _etc.

Thus, all the above positive technical results of the proposed method have been achieved.

Example 1 specific use of the method.

Consider the use of the proposed burst multipath method to obtain a passive headlamp N _l = 5 rays in a pulse-Doppler radar. The radar parameters are as follows: wavelength λ = 10 cm; the number of phase shifters, PAR N _f = 500; the duty cycle of the probe pulses Q _p = 10; the period of the probe pulses T _i.p = 100 μs; range channel width d = 10 m; the number of points of the FFT calculator - N _FFT = 128.

The structure and timing diagram of the radar are shown in FIG. 1 and FIG. 3. Each pack begins with the issuance by the synchronizer in the control system of the pulse of the beginning of the pack C7. The duration of the multipath burst and, accordingly, the period of pulses C7 is T _burst n = N _un ⋅T _and = 640 * 0.1 = 64 ms, where N _un = N _l * N _FFT = 5 * 128 = 640 is the number of probe pulses in the multipath a pack. During the (n-1) -th multi-beam burst from the radar central control center to the SUL via the serial interface, data are received for Nl = 5 directions α1 _n , α2 _n ... α5 _n , in which rays should be exposed in the next n-th burst. Each direction of the ray α is represented by its azimuth and elevation angle. Upon receiving the data for each of JFM Nl = 5 directions from the known relationships [5, pp 613] was calculated as M _^ -bit code phase shifters of all N _{f φ i (α j) [n} ], where j = 1, 2 ... 5 - the number of the direction of the beam, i = 1, 2 ... N _f - the number of the phase shifter; n is the number of multipath packets. The calculations must be completed before the start of the nth pack and their results are stored in RAM.

The transfer of the calculated phases to the corresponding phase shifters for the nth burst begins immediately after the last probe pulse of the previous (n-1) burst arrives after the sync pulse of the beginning of burst C7. Then, during each period of the probe pulses of the nth burst of phase ϕ _i (α _j ) [n], corresponding to the next j-th direction of the beam, they are transferred from RAM SUL to the shift registers of each of i = 1, 2 ... N _f phase shifters. Then, before each probing pulse, using a single clock pulse C2, the phases of all phase shifters are rewritten from their shift registers into parallel registers and fed to the control inputs of the phase shifters.

The data recording in the shift registers of all phase shifters should last no more than the time T _and = 100 μs, which is equal to the period of the probe pulses at the output of the transmitter 7. To ensure this requirement, this record can be performed in parallel in the shift register groups.

The sequence of directions j, for which, in the next k-th (k = 1, 2 ... N _un , N _un = 640) period of the probe pulses of the multipath burst, the phases are set to the phase shifters described above, as follows: j = {1, 2, 3, 4, 5, 1, 2, 3, 4, 5, ... 1, 2, 3, 4, 5.}, i.e. j _k = (k-1) _mod5 +1.

To ensure continuous operation of the LMS, its calculator must provide the ability to receive data from the DAC and calculate the phases of the nth burst simultaneously with the recording of phases in the phase shifters in each period of the probe pulses of the (n-1) multibeam burst, as described above.

At the output of the distributor 11, the echo signals of each of j = 1, 2 ... 5 rays received during the burst have a period of probing pulses T _and = T, _and пN _l = 100 * 5 = 500 μs. the number of pulses per burst N _il = N _ip / N _l = _640/5 = 128, the duration of the intervals of reception of the beam echo T and _ip = 100 μs.

After the end of the interval of receiving an echo signal in a given direction, an echo signal from a greater range does not get into processing, because the receiving beam is set in a direction different from the direction of the corresponding probe beam. At the indicated intervals for receiving the echo signals of each beam, samples N _R = R _mak / d = 1500 range channels are allocated, in accordance with the accepted range channel width d. In each channel of the range of each beam, the calculation of 128 point FFT, Doppler interference filtering and threshold detection of the target.

Thus, in this example the proposed method multipath mode during burst duration T _Pace = 12.8 * 5 = 64 ms, _L = N received beams 5 with an arbitrary direction, with a period T _and pulse = 500 microseconds, _and pulse number N = 128, with a duty cycle Q _m = 10⋅5 = 50, and a pulse duration of t _and = T _i.p / Q _.n = 10 μs, with a complex signal, for example with chirp. The minimum range of the radar in this case will be R _min = t _and * c / 2 = 1500 m, and the maximum R _min = T, _etc. * s / 2 = 15 km. The period of ambiguity in speed is ΔV = λ / (2Т _и ) = 100 m / s. With this ΔV, the speed of all modern UAVs will be measured unambiguously. In addition, almost all targets with high speeds will be detected, as intervals of "blind" speeds, as will be shown below in FIG. 5 are only about 2 m / s.

As shown above, in terms of the viewing rate and detection range, the burst multipath mode obtained by the proposed method is equivalent in terms of the scanning speed N _l = 5 to single-beam packets, in each of which the duration is Tpach = 12.8 ms, the period of the probe pulses T _and = 100 μs, the number pulses N _and = 128 and the duty cycle of the transmission and reception of Q _e = 10. Let us compare the operation of the radar according to example 1 in the burst multipath mode and when using the indicated equivalent single-beam burst to solve the most important task of the invention - selection against the background of passive interference of an inconspicuous low-speed target, for example, a UAV type with a detection range of less than 15 km. For this, in FIG. 5 as a function of speed, exponential models of the energy spectra of passive interference from the earth's surface covered with forest are given in light, medium and strong winds [5. C 52], and the squares of the frequency response of individual filters from the sets of Doppler filters: the 5th filter for the resulting multibeam bundle with a duration of 64 ms and the 3rd filter for the equivalent single-beam packet with a duration of 12.8 ms. The indicated filter sets for both packs were calculated using the FFT with weighting by the Dolph-Chebyshev window with a suppression of 70 dB. From FIG. Figure 5 shows that in the burst multipath method, the suppression of passive interference of 70 dB required with an average wind having a speed of 3 m / s can be obtained with acceptable signal loss of 3 dB at a minimum target speed of 3.3 m / s, which corresponds to the characteristics of modern UAVs . In contrast, in the equivalent single-beam mode, even with a minimum target speed of 9 m / s, the average wind suppression will be only 55 dB. In addition, according to FIG. 5, the speed resolution is 3 dB for the multipath mode in N _l = (6.1 / 1.22) = 5 times less than in the equivalent single-beam mode. This shows a significant advantage of the proposed burst multipath method over the prototype when working on an inconspicuous low-speed target.

Example 2

In the radar of example 1, it is necessary to reduce the minimum detection range from R _min = 1500 m to R * _min = 30 m, with a maximum range of R * _pop = 13.5 km.

To ensure this, at each period of the transmitter pulses, when setting the next direction of the beam to receive and transmit, 2 probing signals, shown in FIG. 4, the first simple pulse with a duration of t1 _and = 2R * _min / s = 0.2 μs and the second complex LFM signal with a duration of t2 _and = 10 μs, with a frequency deviation of ± 2.5 MHz. The time interval between pulses is τ1 = t2 _and = 10 μs. The time interval τ2 = 100-10 = 90 microseconds, which provides the required maximum range _poppy R * = c * τ2 / 2 = 13.5 km. From the range R * _min = 30 m to the range R1 = τ1 * c / 2 = 1500 m, the range is measured at the output of the optimal (matched) filter for the first pulse, and from the range R1 = 1500 m to R * _max = 13.5 km, the range measured at the output of the optimal (matched) for the second filter pulse. In this case, the necessary energy condition is satisfied

In FIG. 6 shows the result of optimal filtering of two echo signals from a target located on the interval τ2 in FIG. 4. Filtering was carried out by a filter consistent with the second pulse and a Gaussian time window with a parameter of 2.5.

From FIG. 6 it is seen that the suppression of echoes "not their own" matched filters is 25 dB. Hence, on the interval τ1, the false signal from the second pulse has a total suppression of more than 25 + 40log (T _and / τ1) = 93 dB, which virtually eliminates its detection. In the interval τ2, the detector must extract serifs from the true compressed echo signal from the second pulse and exclude serifs from its sidewalls, therefore, moreover, such a detector will not miss the false signal from the echo signal of the first pulse with a level another 10 dB less than the level sidewalls.

Example 3

When using the burst multipath review method, it is necessary to take into account 2 additional factors: the finiteness of the AFR phase shifters availability time t _f and the possible instability of the phase shifter parameters corresponding to one beam direction due to intermediate phase code switching between burst pulses.

The typical availability time of a modern discrete S-band phase shifter is t _f = 2 μs, which is why the radar hardware range decreases by only 300 m.

The indicated instability of the phase shifter parameters leads to random, from pulse to pulse, changes in the BOTTOM, which gives additional radar noise, the standard deviation of which can be estimated by the formula [5, C. 628]:

where δ _ϕ and δ _A are the maximum tolerance on the instability of the phase and the transfer coefficient (loss) of the phase shifter; N _fv - the number of phase shifters PAR. For example, at N _fv = 500 to obtain allowable noise with

σ _fv = 10 ^-7 = -70 dB, tolerances δ _ϕ = 0.015≈1 ° and δ _A = 0.015≈0.13 dB are required, which is achievable.

As a result of comparing the proposed method not only with the prototype and the closest analogs, but also with other technical solutions in this technical field, according to the applicant and the authors, the claimed radar method for detecting inconspicuous targets in a pulse-Doppler radar with a PAR has a combination of essential features, not known from the prior art for objects of this purpose, which allows us to conclude that the criterion of "novelty" for the invention. Also, the claimed method, according to the applicant and the authors, meets the criterion of "inventive step", because for specialists, it does not explicitly follow from the prior art, i.e. not known from available sources of scientific, technical and patent information at the filing date. The above examples of the use of the proposed method show its compliance with the criteria of "industrial applicability" and effectiveness. In addition, in the future, the inter-pulse switching of the directions of the rays proposed in the invention may find other useful applications.

Sources of information adopted in the preparation of the description of the invention

1. A method for detecting stealth unmanned aerial vehicles. Patent RU 2534217 C1 (2013). IPC G01S 13/04 (2006/01).

2. Anenkov A.E. and others. On the observation of small unmanned aerial vehicles. Proceedings of the Moscow Aviation Institute. Vol. 91. C 2-18.

3. Sinawi A.I. et al. Control of the shape of the radiation pattern in antenna systems with electronic beam control. Antennas 2005 No. 2 (93), C 27-32.

4. Multipath radars as part of security systems. Anti-terror. Ed. I.K. Antonova. M: Radio engineering 2017 S. 23.

5. Reference radar. Ed. M.I. Skolnik. M: Technosphere 2014. T1.

6. Bakulev P.A., Stepin V.M. Methods and devices for moving targets selection. M .: "Radio and communications", 1986. S. 98.

Claims (2)

1. A radar method for detecting inconspicuous targets in a pulse-Doppler radar station (radar) with a phased array (PAR), in which, using a transmitter and a beam control system, PAR, transmit sounding pulses, and using a single-channel, series-connected receiver, analog- a digital converter, an echo-to-video converter, an optimal filter, an echo-signal distributor for individual channels, and moving target selection systems detection of moving targets, characterized in that, using the PAR control beam system, during the burst of probe pulses before each probe pulse with a cycle equal to the number of beams generated during the burst, the direction of the transmitted and received PA beam is changed, the echo signal distributor is distributed on the video frequency readings both on the ray channels, in accordance with the direction of the rays in a given period of the probe pulses, and on the distance channels in each of the ray channels, by the moving target selection system d, having the number of channels equal to the product of the number of rays by the number of range channels, detect moving targets and set the pulse period of the transmitter corresponding to the instrumental range of the radar. 2. The radar method for detecting inconspicuous targets in a pulse-Doppler radar with a PAR according to claim 1, characterized in that for one direction of the transmitting and receiving beams, the probe pulse is divided into two probe pulses, the first of which is simple, short in duration, corresponding to a given minimum range the target and the required resolution in range, the second pulse is a complex, long duration corresponding to a given maximum detection range of the target and the required resolution in range, set inter the shaft between the probe pulses is greater than or equal to the duration of the second pulse, while when receiving in the interval between the probe pulses, the echo signal is processed optimally for the first pulse, and in the interval after the second pulse until the end of the period, the echo signal is processed optimally for the second pulse and the processing results detect a moving target.

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