RU2800494C1 - Device for digital signal processing in pulsed-doppler radar with compensation of target migration by range and fm doppler signals in one period of radiating and receiving radio pulses - Google Patents

Abstract

FIELD: radars.

SUBSTANCE: invention is intended for use in pulse-Doppler radar stations (RLS) operating with high-speed and highly manoeuvrable targets. The claimed device comprises a digital shaper of quadrature components, a matched filter, three long-range-time portrait shapers, a long-range-frequency portrait shaper, a module calculator, a threshold processing unit, a fast Fourier transform processor, a spectrum matrix shaper, two element-by-element matrix multipliers, and an inverse fast Fourier transform processor, a phase multiplier calculator, a phase factor matrix generator, an autofocus signal generator, an amplitude spectrum calculator, an amplitude spectrum symmetry centre calculator, and a reference signal matrix generator. The listed components of the claimed device are interconnected in a certain way.

EFFECT: increased speed resolution of the radar when working with high-speed and highly manoeuvrable air targets.

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Description

The invention relates to the field of radar and is intended for use in pulse-Doppler (ID) radar stations (RLS) operating with high-speed and highly maneuverable targets. Achievable technical result is to increase the speed resolution of the radar when working with high-speed and highly maneuverable air targets.

Modern ID radars, as a rule, operate in several modes. The first and main is the space review mode, in which the search and detection of targets (single and group) is carried out with an assessment of their parameters (range and speed). Another mode may be the mode of resolving nearby targets, which allows you to resolve nearby targets in a group, determine their number and more accurately evaluate the parameters of each target.

A device for digital signal processing (DSP) in the ID radar with compensation for target migration in range is known, the description of which is presented in patent No. 2673679 of the Russian Federation [1]. The specified device is designed to operate in the mode of resolving high-speed targets and uses information about the parameters of the target obtained after the first sounding and receiving echo signals (in the detection mode). In the device, after the second probing and receiving echo signals coming from the output of the intermediate frequency amplifier, the complex envelopes of the echo signals are calculated using a digital quadrature component generator (DFCCS), and the signals are matched filtered (SF). In the fast Fourier transform (FFT) processor, discrete Fourier transform (DFT) samples are calculated, from which a matrix of spectra of received echo signals is formed.

Simultaneously with the start of operation of the device in the target resolution mode, the second (information) input of the device receives the target designation obtained from the results of processing the echo signals of the first sounding (in the detection mode) about the speed of the moving target, with the help of which the phase factor generator (PM) calculates the PM and forms a matrix FM. Then, in the element-by-element matrix multiplier, the spectrum matrix and the FM matrix are multiplied. The obtained results of the element-wise multiplication are fed to the inverse FFT processor (IFFT), where the IFFT of the corrected echo signal spectra of each sounding period is performed. Next, a long-range temporal portrait (DVP) and a range-frequency portrait (LFP) of targets are formed. According to the maximum values of the modules of the DFS signals, the specified range of the detected single and permitted group targets is determined.

The disadvantage of the described device is that during its operation two periods of radiation and reception of a burst of radio pulses are performed. The first period is used to obtain information about the target's speed (in the detection mode), the second - directly to compensate for the migration of high-speed targets in range (in the resolution mode).

This shortcoming is devoid of a device for digital signal processing of the ID radar with compensation for the migration of high-speed targets in range in one period of radiation and reception of a burst of radio pulses, described in patent No. 2782249 of the Russian Federation [2]. The device operates in two cycles (after one period of radiation and reception of a burst of radio pulses): for the first cycle, the target speed is determined, for the second, the migration of targets in range is directly compensated.

However, in addition to moving at high speed, modern air targets during flight have rather large accelerations (highly maneuverable targets), which reduce the potential speed resolution of the radar. With this type of targets, the DSP device in the ID radar works with compensation for frequency modulation (FM) of Doppler signals in one period of radiation and reception of a burst of radio pulses, a description of which is presented in patent No. 2782574 of the Russian Federation [3]. In the specified device, the input analog signals are converted into digital form, their complex envelopes are extracted, and the SF of the echo signals is performed. The samples of the received signals of each probing period are fed into the DWT shaper matrix. Next, the signals are fed to the DFS shaper, in which the DFT samples of the Doppler signals corresponding to each range element are calculated. The obtained readings of the DFS are sent to the module calculator, where their modules are determined. The readings exceeding the threshold in the threshold processing block are sent to the output of the device and can be used to detect, estimate the range and speed of targets.

After detecting and evaluating the target parameters from the threshold processing unit, the target designation about the range of a moving highly maneuverable target is sent to the DWP shaper (i _D is the row number in the two-dimensional DFS matrix with the maximum amplitude corresponding to the target range, and N _E is the number of rows of readings by range in the two-dimensional matrix DFS corresponding to the assessment of the duration according to the range of the target).

According to the target designation about the range of a highly maneuverable target, N _E lines are read from the DWP generator, symmetrically located relative to the target designation in range i _D , into the autofocus signal (AF) signal generator, in which, by forming time-shifted and complex-conjugate Doppler signals, multiplying the signals and inverting the sign AF signals are generated. The received AF signals are fed to the amplitude spectrum calculator, in which the FFT procedure for N _E lines is performed, the modulus is calculated, and the amplitude spectra of the AF signals are averaged and centered. Next, the signal enters the calculator of the center of symmetry of the amplitude spectrum, in which the autoconvolution of the incoming signal is calculated and the coordinate corresponding to the maximum of the calculated function is determined. Using the obtained result, the FM index of the Doppler signal is calculated in the reference signal matrix generator and the reference signal matrix is formed to compensate for the spurious FM. After the element-by-element multiplication of the generated reference signal matrix and the previously obtained DWT matrix, Doppler signals with compensated spurious FM are formed at the output of the multiplier of the element-by-element matrix multiplier. Further, the signal counts are fed to the DFS shaper, the module calculator and the threshold processing unit, the output signals of which are used to confirm the detection, clarify the speed of objects and increase the speed resolution of the radar of highly maneuverable targets.

The described devices make it possible to compensate for the migration of high-speed targets in range or to compensate for the FM Doppler signals of highly maneuverable targets. This makes it possible to separately operate the radar with both high-speed and highly maneuverable air targets.

However, in practice, it is not known a priori what type of targets (high-speed or highly maneuverable) will have to work with. Therefore, the disadvantage of the known devices is the inability to simultaneously compensate for the migration of high-speed targets in range and demodulate the spurious FM Doppler signals of highly maneuverable targets.

The aim of the invention is a DSP device that allows for one period of radiation and reception of a burst of radar pulses to compensate for the migration of high-speed targets in range and FM Doppler signals of highly maneuverable targets.

The closest analogue of the claimed invention in terms of technical essence is a device for DSP ID radar with compensation for the migration of high-speed targets in range in one period of radiation and reception of a burst of radio pulses, described in patent No. 2782249 of the Russian Federation [2]. Let's take it as a prototype.

In this device, an analog intermediate frequency signal is fed to the input of the DSFCS, in which samples of the quadrature components are digitally formed (the signal is digitized, multiplied by the exponential, filtered in digital low-pass filters, followed by decimation of the output samples) [4].

The readings of the quadrature components of the signal are fed to the input of the SF, in which the SF of echo signals is performed in the time domain using a non-recursive digital filter or in the frequency domain using the “fast” convolution method [4].

Next, the echo signal counts of each probing period are fed into the DWP shaper, in which the signal realizations corresponding to each probing are recorded column by column into the random access memory of the DWP shaper.

Samples of echo signals of a two-dimensional matrix from the first output of the DWP shaper are fed to the first input of the DFS shaper, in which the spectral analysis of the signal samples of each row of the matrix is performed using the FFT processor, which is part of the DFS shaper.

The resulting signal spectra corresponding to each range element are fed to the input of the module calculator, where the modules of the complex readings of the DFS signals are determined, which then enter the threshold processing unit. In the specified block, the modules are compared with the threshold, based on the results of which a decision is made to detect the target and its range and speed are estimated.

After determining the target speed, information about the target speed is received from the output of the threshold processing unit to the input of the FM calculator. In the PM calculator, phase factors are calculated to correct the range migration of SF responses in each probing period, and in the PM matrix shaper, a PM matrix is formed for all probing periods of a burst of radio pulses.

Simultaneously, from the control output of the threshold processing unit, a control signal is supplied to the DWT shaper for re-reading the existing DWT matrix.

From the second output of the DWT shaper, the samples of the echo signals of the two-dimensional matrix are fed to the FFT processor, in which the DFT samples are calculated. The spectral components of the echo signal are recorded in the corresponding to the given probing period column of the shaper of the spectra matrix. During the period of accumulation of a burst of echo signals in this shaper, a matrix of echo signal spectra is formed.

In the element-by-element matrix multiplier, the two matrices received at the inputs are multiplied, which results in a two-dimensional matrix, each element of which is the product of the corresponding matrix elements obtained in the spectrum matrix generator and in the FM matrix generator.

The resulting two-dimensional matrix is fed into the IFFT processor, where the IFFT procedure is performed on the columns. As a result, we obtain a matrix, the columns of which are time-corrected signal realizations corresponding to each sounding (target migration in range has been compensated).

From the output of the IFFT processor, the two-dimensional matrix enters the second input of the DFS generator, in which the signal samples of each line corresponding to one range are subjected to spectral analysis in the FFT processor, which is part of the DFS generator.

Further, in the calculator of the module, the modules of the complex readings of the DFS signals are determined, which are then compared with the threshold in the threshold processing block. Information about target detection, its specified range and speed is fed to the output of the device.

As a result of the proposed processing in the ID radar for one period of radiation and reception of a burst of radio pulses, the signal-to-noise ratio (SNR) at the output increases and the resolution in the range of high-speed targets improves.

The disadvantage of the prototype is the inability for one period of radiation and reception of a burst of radio pulses used to compensate for the migration of high-speed targets in range, and also demodulate the spurious FM Doppler signals of highly maneuverable targets.

The present invention is aimed at overcoming this disadvantage of the prototype.

The technical result of the claimed invention is to increase the speed resolution of the radar when working with high-speed and highly maneuverable air targets.

The specified technical result is achieved by the fact that in a known device containing serially connected DSFKS, the input of which is the input of the device, the SF, the DVP shaper, the DFS shaper, the module calculator, the threshold processing unit, the first output of which is the first output of the device, the second control output of which is connected to the second control input of the DWT shaper, as well as an FFT processor, a spectrum matrix shaper, an element-wise matrix multiplier, an IFFT processor, connected in series to the second output of the DWT shaper, and a FM calculator and a FM matrix shaper connected in series to the first output of the threshold processing unit, the output of which is connected to the second by the input of the element-by-element multiplier of the matrices, a DWP 2 generator, an AF signal generator, an amplitude spectrum calculator, an amplitude spectrum symmetry center calculator, a reference signal matrix generator, are introduced; element-by-element matrix multiplier 2, DWT generator 3, the output of which is connected to the second input of the DFS generator, and the second input of the element-by-element matrix multiplier 2 is connected to the second output of the DWT 2 generator, the first input of which is connected to the output of the IFFT processor, and the second input is connected to the third output of the block thresholding, which is the second output of the device.

Due to the introduction of a set of essential distinctive features into the known prototype device, the proposed device provides the technical result of the invention - increasing the speed resolution of the radar when working with high-speed and highly maneuverable air targets.

The essence of the invention is illustrated by a block diagram shown in the figure, where it is indicated:

1 - CFKS;

2 - SF;

3 - shaper fiberboard 1;

4 - shaper DSP;

5 - module calculator;

6 - block thresholding;

7 - FFT processor;

8 - spectrum matrix shaper;

9 - element-by-element matrix multiplier 1;

10 - OBFT processor;

11 - shaper fiberboard 2;

12 - FM calculator;

13 - shaper matrix FM;

14 - AF signal conditioner;

15 - amplitude spectrum calculator;

16 - calculator center of symmetry of the amplitude spectrum;

17 - shaper matrix of the reference signal;

18 - element-by-element matrix multiplier 2;

19 - shaper fiberboard 3.

The input of the device is the input of the CFKS (1), the output of which is connected to the input of the SF (2), the output of which is connected to the input of the shaper DVP 1 (3), the first output of which is connected to the first input of the shaper FFS (4), and the second output is connected to the input FFT processor (7), the output of which is connected to the input of the spectrum matrix shaper (8), the output of which is connected to the first input of the element-wise matrix multiplier 1 (9), the output of which is connected to the input of the IFFT processor (10), the output of which is connected to the first input of the shaper DVP 2 (11), the first output of which is connected to the input of the AF signal shaper (14), the output of which is connected to the input of the amplitude spectrum calculator (15), the output of which is connected to the input of the calculator of the center of symmetry of the amplitude spectrum (16), the output of which is connected to the input reference signal matrix shaper (17), the output of which is connected to the first input of the element-by-element matrix multiplier 2 (18), the output of which is connected to the input of the DVP shaper 3 (19), the output of which is connected to the second input of the DFS shaper (4), the output of which is connected to the input of the module calculator (5), the output of which is connected to the input of the threshold processing unit (6), the first output of which is the first output of the device and is connected to the input of the FM calculator (12), the output of which is connected to the input of the FM matrix shaper (13), the output of which connected to the second input of the element-by-element matrix multiplier 1 (9); the third output of the threshold processing unit (6) is the second output of the device and is connected to the second input of the shaper DWP 2 (I), the second output of which is connected to the second input of the element-by-element matrix multiplier 2 (18); the control (second) output of the threshold processing unit (6) is connected to the control (second) input of the DVP shaper 1 (3).

The DSP device in the ID radar with target migration compensation in range and FM Doppler signals in one period of radiation and reception of a burst of radio pulses operates in three cycles as follows.

At the first cycle, an analog intermediate frequency signal is received at the input of the device from the output of the radar receiver and is fed to the input of the DSFCS (1), in which the readings of the quadrature components are digitally formed.

The obtained samples are fed to the input of the SF (2), where the echo signals are matched filtered in the time domain using a non-recursive digital filter or in the frequency domain using the “fast” convolution method [4].

Next, the echo signal samples of each probing period are fed into the shaper DWP 1 (3), in which the signal realizations corresponding to each probing are written column by column into the random access memory of the shaper DWP 1 (3).

The samples of the echo signals of the two-dimensional matrix from the first output of the shaper DFT 1 (3) are fed to the first input of the shaper DFS (4), in which the spectral analysis of the samples of the signals of each row of the matrix is performed using the FFT processor, which is part of the shaper DFS (4).

The resulting signal spectra corresponding to each range element are fed to the input of the module calculator (5), where the modules of the complex readings of the DFS signals are determined, which then enter the threshold processing unit (6). In the specified block, the modules are compared with the threshold, based on the results of which a decision is made to detect the target and its range and speed are estimated.

After determining the target speed from the first output of the threshold processing unit (6), information about the target speed is sent to the input of the FM calculator (12). In the FM calculator (12), phase factors are calculated to correct migrations according to the range of SF responses in each sounding period, and in the FM matrix generator (13), a matrix of phase factors is formed for all sounding periods of a burst of radio pulses.

Simultaneously, from the control output of the threshold processing unit (6), a control signal is supplied to the DWP generator 1(3) for re-reading the existing DWP matrix and the second processing cycle begins.

From the second output of the shaper DWP 1 (3) the samples of the echo signals of the two-dimensional matrix are fed to the FFT processor (7), in which the DFT samples are calculated. The spectral components of the echo signal are recorded in the column of the spectrum matrix shaper (8) corresponding to the given probing period, where a matrix of echo signal spectra is formed for the period of accumulation of a burst of echo signals.

In the element-by-element matrix multiplier 1 (9), the two matrices received at the inputs are multiplied, which results in a two-dimensional matrix, each element of which is the product of the corresponding matrix elements obtained in the spectrum matrix generator (8) and in the FM matrix generator (13).

The resulting two-dimensional matrix is fed into the IFFT processor (10), which performs the IFFT procedure on the columns. As a result, we obtain a matrix whose columns represent time-corrected signal realizations corresponding to each sounding (target migrations in range have been compensated).

From the output of the IFFT processor (10), the two-dimensional matrix is fed to the first input of the shaper DWP 2 (11), and from the third output of the threshold processing unit (6) to the second input of the shaper DWP 2 (11), the target indication about the range of the moving target is received, after which the third begins processing cycle.

From the DWP 2 (11) generator, N _E lines are read, symmetrically located relative to the target designation in range i _D , and enter the AF signal generator (14), in which, by generating time-shifted and complex-conjugate Doppler signals, multiplying the signals and inverting the sign N _E AF signals are formed. The received AF signals are fed to the amplitude spectrum calculator (15), in which their DFTs are calculated using the FFT algorithm and its modulus. Then, the average amplitude spectrum is calculated from the input N _E amplitude spectra of the AF signals (incoherent accumulation of spectra to increase the SNR) and the mathematical expectation is eliminated from the resulting signal.

From the output of the amplitude spectrum calculator (15), the averaged centered amplitude spectrum of the AF signal enters the calculator of the center of symmetry of the amplitude spectrum (16), in which the autoconvolution of the averaged centered amplitude spectrum is calculated by the “fast” convolution method and the coordinate corresponding to the maximum of the calculated function is determined.

The value of the coordinate obtained in the calculator of the center of symmetry of the amplitude spectrum (16) is used in the generator of the reference signal matrix (17) to calculate the FM index of the Doppler signal and generate the reference signal necessary to compensate for the parasitic FM in the input signal. At the output (17), a reference signal matrix is formed, in which each row is equal to the reports of the found reference signal, and the number of rows is equal to N _E - the number of range elements in the probing period, symmetrically located relative to the target designation in range i _D .

The generated reference signal matrix is fed to the first input of the element-by-element multiplier of matrices 2 (18), the second input of which is supplied with DWP 2 from the second output of the DWP shaper 2(11).

In the element-wise matrix multiplier 2 (18), the incoming matrices are multiplied, resulting in a two-dimensional matrix, each element of which is a product of the corresponding matrix elements. At the output of the matrix multiplier 2 (18), Doppler signals are formed with a compensated spurious FM due to the accelerated movement of targets, which then enter the shaper DWP 3 (19), at the output of which DWP 3 is formed.

The resulting DWP 3 is fed to the second input of the DFS shaper (4), in which the DFT counts of the demodulated Doppler signals corresponding to each range element are calculated. The obtained readings of the DFS are fed into the calculator of the module (5), where the modules of the complex readings of the spectra of the Doppler signals are determined.

Next, the sample modules enter the threshold processing unit (6) and are compared with the threshold. From the output of the threshold processing unit (6), information about the target parameters is fed to the outputs of the device and can be used to refine the range and speed of high-speed and highly maneuverable targets.

Thus, the present invention provides a technical result, which consists in increasing the speed resolution of the radar when working with high-speed and highly maneuverable air targets.

Information sources:

1. Patent 2673679 RF, IPC 2006.01, G01S 13/53. Device for digital signal processing in a pulse-Doppler radar with range target migration compensation / I.I. Markovich, E.E. Tomorrow. Applicant and patent holder - PJSC Aviation Holding Company Sukhoi, JSC Research Institute of Instrument Engineering named after V.V. Tikhomirov, Federal State Autonomous Educational Institution of Higher Education "Southern Federal University". - 2017136678. Application: 10/17/2017. Published: 11/29/2018. Bull. No. 34.

2. Patent 2782249 RF, IPC 2006.01 G01S 13/53, G01S 7/292. Device for digital signal processing in a pulse-Doppler radar with compensation for target migration in range for one period of radiation and reception of a burst of radio pulses / I.I. Markovich, E.E. Tomorrow. Applicant and patent holder - FGAOU VO "Southern Federal University". - 2021139734. Application: 12/28/2021. Published: 25.10.2022. Bull. No. 30.

3. Patent 2782574 RF, IPC 2006.01 G01S 13/53, G06F 17/14. Device for digital signal processing in a pulse-Doppler radar with FM compensation of Doppler signals for one period of radiation and reception of a burst of radio pulses / I.I. Markovich. Applicant and patentee - FGAOU VO "Southern Federal University". - 2021139724. Application: 12/28/2021. Published: 31.10.2022. Bull. No. 31.

4. Markovich I.I. Digital signal processing in systems and devices: monograph / I.I. Markovich. - Rostov n / a: Publishing House of the Southern Federal University: 2012. - 236 p.

Claims (1)

A device for digital signal processing in a pulse-Doppler radar with compensation for target migrations in range and FM Doppler signals for one period of radiation and reception of a burst of radio pulses, containing serially connected digital shaper of quadrature components, the input of which is the input of the device, a matched filter, a shaper of the range-time portrait , a long-range-frequency portrait shaper, a module calculator, a threshold processing unit, the first output of which is the first output of the device, the second control output of which is connected to the second control input of the long-range-time portrait shaper, as well as the processor connected in series to the second output of the long-range-time portrait shaper FFT, spectrum matrix generator, element-by-element matrix multiplier, inverse FFT processor and serially connected to the first output of the threshold processing unit, a phase multiplier calculator and a phase factor matrix generator, the output of which is connected to the second input of the element-by-element matrix multiplier, characterized in that a second generator connected in series is introduced distance-time portrait, autofocus signal generator, amplitude spectrum calculator, amplitude spectrum symmetry center calculator, reference signal matrix generator, second element-by-element matrix multiplier, third long-range-time portrait generator, the output of which is connected to the second input of the distance-frequency portrait generator, and the second the input of the second element-by-element matrix multiplier is connected to the second output of the second long-range-time portrait shaper, the first input of which is connected to the output of the inverse FFT processor, and the second input is connected to the third output of the threshold processing unit, which is the second output of the device.

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