RU2782575C1 - System for selection of moving targets with measurement of range, radial velocity and direction of movement in each period of sounding - Google Patents

Abstract

FIELD: radar technology.

SUBSTANCE: invention relates to the field of radar, namely to active radar systems, and is intended to solve the problem of selecting moving targets and simultaneously measuring their range, radial velocity and direction of movement. The claimed system for selection of moving targets (SMT) measures the range, radial velocity and direction of movement in each period of sounding. The system contains a digital shaper of quadrature components, a pair of random-access memory devices, a matched filter with a connected permanent storage device, a module calculator, a pair of subtractors, calculators of the time position of the maximum and minimum, an adder, calculators of range, radial velocity and direction of movement. A pair of signal switches has been introduced into the claimed system.

EFFECT: doubling the rate of obtaining operational information (range, radial velocity and direction of movement of the target).

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Description

The invention relates to the field of radar and can be used in radar systems (RLS) for the selection of moving targets (MTS) with the measurement of their range, as well as the module and sign of the radial velocity.

Known similar in purpose methods and devices SDC, designed to suppress reflections from stationary and slowly moving objects in active radar systems.

In US patent US 3225349 A dated December 21, 1965 [1], a moving target selection radar (MTS) is described, in which a group of two sounding pulses with linear frequency modulation (chirp) is formed, having opposite signs of frequency deviation. This group is radiated towards the target. The reflected signal is received, amplified, divided into two channels and fed to matched filters (SF). Each of the filters is matched to one of the two emitted pulses. The filter-matched pulse generates a compressed SF response, while the unmatched pulse receives additional phase dispersion and its energy is distributed over an interval equal to twice the original duration. After that, the signal of one channel passes the delay line to equalize the time position of the pulses in the group. If a group of pulses reflected from a moving target, the peaks of the compressed pulses shift in time in different directions from the moment determined by the distance to the target, and this shift is a function of the Doppler frequency, taking into account the sign of the probing signal frequency deviation. If a group of pulses is reflected from a stationary target, the peaks of the compressed pulses do not shift relative to each other and the time point determined by the distance to the target. Further, the signals are fed to the subtractor. If the target is moving, then the output of the device will be a difference signal, which is compressed responses of SF of different polarity shifted in time relative to each other, which can later be used to determine the speed and range of the target. In the case of a stationary target, the signal at the output of the subtractor is zero.

The described radar with SDC has a number of significant drawbacks.

The increased emission time, determined by the duration of the emitted burst, equal to two chirp durations and the interval between them, limits the minimum range at which moving targets can be detected.

The patent states that with the help of additional processing it is possible to determine the range, speed and direction of the target, but this is not confirmed by the description of the corresponding algorithm and the structure of the device. Thus, the patent does not provide a solution that allows the device to simultaneously measure the range, speed and direction of the target.

Known technical solution is described in US patent US 5870054 A dated 09.02.1999 [2], which considers the radar with SDC with compensation for the effect of "blind speeds", the basic principle of operation of which does not differ from that discussed above. The system described in US Pat. No. 5,870,054 A uses a chirp signal with an interperiod reversal of frequency deviation. This allows you to reduce the "dead zone" of the radar. The interval between the envelopes of compressed pulses at the output of the subtractor is directly proportional to the speed of the target, and the true distance to the target corresponds to the average value of the delays of two pulses.

However, the device described in US Pat. No. 5,870,054 A has the same drawbacks, consisting in the absence of a description of a technical solution that allows measuring the range and speed of a moving target, as well as determining its direction of movement, which is extremely important in a real operational environment.

Another technical solution is described in articles [3, 4]. The principle of operation of the SDC system is similar to that given in US patent 5870054 A, an implementation of the SDC system using digital signal processing is described. In these articles, theoretical information is given about the delays that compressed pulses acquire with different signs of frequency deviation at the output of the SF when reflected from a moving target. However, there is no description of the technical solution that would allow determining the sign of the radial velocity.

Closest to the claimed invention is the technical solution described in patent RU 2626380 C1 [5]. Let's take it as a prototype.

The block diagram of the SDC system proposed in patent RU 2626380 C1 is shown in Fig. 1. The system is designed to isolate signals from moving targets against the background of reflections from stationary and slowly moving objects, as well as passive interference.

The system requires alternating emission of probing chirp pulses with different signs of frequency deviation. In odd periods, pulses with an increasing instantaneous filling frequency (positive frequency deviation) are emitted, in even periods, pulses with a decreasing instantaneous filling frequency (negative frequency deviation) are emitted.

The received reflected signals are transferred to an intermediate frequency and digitized (time sampling and level quantization). After that, the quadrature components are selected (transfer of the signal to the zero carrier frequency). These conversions are performed by the digital quadrature component generator (DFCCS) 1.

The samples of the quadrature components (complex envelope) are fed to a two-page random access memory 1 (RAM1) 2, where the samples are accumulated to perform matched filtering in the spectral region (using a fast convolution algorithm). RAM1 introduces a delay of one probe period.

The quadrature components (complex envelope of the radio signal) are processed in a matched filter (SF) 3. The samples of the complex frequency response (CFC) of the SF are extracted from read-only memory (ROM) 4, and in even periods the CFC is extracted, consistent with the complex envelope of the signal with a positive frequency deviation , in odd periods - consistent with the complex envelope of the signal with a negative frequency deviation.

The signal from the SF output is fed to the input of the module calculator (CM) 5 and then to the inverting input of the subtractor 1 (B1) 6 and to the input of the two-page random access memory 2 (RAM2) 7, which plays the role of a delay line for one probing period. The signal from the output of RAM2, delayed by one probing period, is fed to the non-inverting input B1.

When a signal is reflected from a moving target, a signal is generated at the output B1 in the form of a pair of pulses of the opposite sign. Based on the time interval between the maximum and minimum of the difference signal during odd sounding periods, the estimated range of the target D _R , its radial velocity V _R and direction of motion are estimated.

With the help of time position calculators (GDP) maximum 8 and minimum 9, adder (C) 10 and subtractor 2 (B2) 11, as well as distance calculators (VD) 12, radial velocity (VRS) 13 and direction of movement (VND) 14 are determined D _R , V _R and sgn(V _R ).

The operation of the system (when processing chirp signals reflected from a receding target, V _R >0) is explained by the time diagrams shown in FIG. 2. The technical solution chosen as a prototype ensures the determination of the range, speed and direction of movement of the object only during odd periods of radiation, that is, the frequency of updating information about the target is twice as low as the repetition rate of the probing pulses. This limitation should be considered a significant drawback, since in modern radars, the speed of making a decision on detecting a target and obtaining estimates of its range, speed, and direction of movement is of decisive importance.

The present invention is aimed at overcoming the indicated drawback of the prototype and provides simultaneous measurement of the range, speed and direction of the target in each sounding period.

The specified technical result is achieved by the fact that in a well-known SDC system containing serially connected CFKS, RAM1, SF with a connected ROM, the control input of which is connected to the control input of the SDC system, VM, the output of which is connected to the input of RAM2, as well as B1, the output of which is connected with the inputs of the GDP maximum and the GDP minimum, the adder, the inputs of which are connected to the outputs of the GDP maximum and the GDP minimum, B2, the non-inverting input of which is connected to the output of the GDP maximum, and the inverting input - to the output of the GDP minimum, connected to the output of the VD adder, from the output of which receive an estimate of the range to the target, connected to the output B2 of the VRS, from the output of which the value of the module of the radial velocity of the target is obtained, as well as connected to the output of the B2 VND, from the output of which the sign of the radial velocity of the target is obtained, the signal switch 1 (KS1), the first and second are introduced the inputs of which are connected respectively to the outputs of the VM and RAM2, the control input is connected to the control input of the ROM, and the output is connected n to the non-inverting input B1, and the signal switch 2 (KS2), the first and second inputs of which are connected respectively to the outputs of the VM and RAM2, the control input is connected to the control input of the ROM, and the output is connected to the inverting input B1.

Due to the introduction of a set of essential distinguishing features into the well-known SDS system, the proposed SDS system provides the technical result of the invention - the ability to carry out the SDS with the simultaneous determination of the range, speed and direction of movement of objects twice as often as the prototype - in each sounding period.

The essence of the invention is illustrated by the block diagram shown in Fig. 3, where it is indicated:

1 - digital shaper quadrature components (DSFKS);

2 - random access memory 1 (RAM 1);

3 - matched filter (SF);

4 - read only memory (ROM);

5 - module computer (VM);

6 - random access memory 2 (RAM2);

7 - signal switch 1 (KS1);

8 - signal switch 2 (KS2);

9 - subtractor 1 (B1);

10 - calculator of the temporary position (GDP) of the maximum;

11 - GDP minimum;

12 - adder (C);

13 - subtractor 2 (B2);

14 - range computer (VD);

15 - radial velocity calculator (VRS);

16 - computer direction of movement (VND).

The SDC system with the measurement of the range, radial velocity and direction of the object in each sounding period works as follows.

комплексной огибающей (КО) входного сигнала с периодом дискретизации Т.The reflected signal is transferred to the intermediate frequency and fed to the input of the system. The input analog signal x _BH (t), which is a periodic sequence of chirp radio pulses with an interperiod change in the sign of the frequency deviation, is fed to the input of the DSFCS 1, the device and principle of operation of which are described in detail in [6, 7]. In the DSFKS, the signal x _BX (t) is converted into digital readings

complex envelope (CO) of the input signal with a sampling period T.

In odd probing periods (starting from the first one), QoS signal samples with a positive frequency deviation are recorded in the first page of RAM1 2, and QoS signal samples with a negative frequency deviation are recorded in the second page of RAM1 2 in even probing periods (starting from the second).

In odd probing periods (starting from the third) from the second page of RAM1 2 to the input of the SF 3, the samples of the QoS signal with a negative frequency deviation are received, in even periods of probing (starting from the second) from the first page of the RAM1 2 to the input of the SF 3, the CO samples of the signal with positive deviation.

From ROM 4 to SF 3 in odd periods of probing, samples of the transfer function H ₁ (k) are supplied for consistent processing of chirp signals with a negative sign of the frequency deviation, and in even periods of probing - samples of the transfer function H ₂ (k) for consistent processing of chirp signals with positive frequency deviation.

ROM 4 is controlled by the signal U _control (t) (control voltage), which in odd probing periods is high (logical one), and in even probing periods is low (logical zero).

КО сжатого сигнала с выхода СФ 3 подаются на вход ВМ 5, на выходе которого формируются отсчеты амплитудной огибающей КО сжатого сигнала x_ВМ(nТ) в соответствии с выражениемcountdowns

QS of the compressed signal from the output of SF 3 are fed to the input of VM 5, at the output of which samples of the amplitude envelope of the KO of the compressed signal x _VM (nT) are formed in accordance with the expression

As shown in [8, 9], if the target moves relative to the antenna with a radial velocity v _R , then the maximum amplitude envelope of the compressed signal has a delay

- запаздывание, определяемое расстоянием до цели;where

- delay, determined by the distance to the target;

DR - range to the target;

c - speed of signal propagation;

- запаздывание, определяемое радиальной скоростью; (3)

- delay, determined by the radial velocity; (3)

τ _and - pulse duration;

Δf - frequency deviation of the chirp signal;

- длина волны излучаемого сигнала;

- wavelength of the emitted signal;

f ₀ - carrier frequency of the emitted signal;

- радиальная скорость цели (скорость положительная, если цель удаляется).

- radial speed of the target (the speed is positive if the target is moving away).

Thus, the sign of v _R and the sign of Δf determine the sign of the shift Δt _V of the maximum amplitude envelope of the compressed signal relative to the moment Δt _D .

The readings of the amplitude envelope of the signal from the output of the VM 5 are fed to the input of the RAM2 6, to the first input of the KS1 7 and to the first input of the KS2 8.

Block KS1 7 is a key controlled by the signal U _control (t). In even periods of probing KS1 7 transmits to the non-inverting input B1 9 the signal x _BM (nT), in odd periods - the signal x _RAM2 (nT). Block KS2 8 is similar to KS1 7 and is also controlled by the signal U _control (t). In even periods of probing, KS2 8 transmits to the inverting input B1 9 signal x _RAM2 (nT), in odd periods - signal x _BM (nT).

Thus, (taking into account the delay introduced by RAM1 2 and RAM2 6) in each probing period at the output B1 9 the difference between the envelope of the compressed signal with positive deviation and the envelope of the compressed signal with negative deviation is formed. The resulting difference of the envelopes x _B1 (nT) is fed to the inputs of the GDP maximum 10 and GDP minimum 11 of the difference signal.

From the output of the GDP maximum 10, the value of n _max equal to the delay of the maximum of the difference signal relative to the moment of radiation, expressed in sampling periods, is fed to the first input C 12 and to the non-inverting input B2 13.

From the output of the GDP minimum 11, the value of n _min , equal to the delay of the minimum of the difference signal relative to the moment of radiation, expressed in sampling periods, is fed to the second input C 12 and to the inverting input B2 13.

, значение которой хранится в памяти ВД 14. Таким образом на выходе ВД 14 получается уточненная оценка дальности D_R до цели, которая не содержит погрешностей, обусловленных движением цели:From the output C 12, the value n _max + n _min is fed to the input of the VD 14, in which it is multiplied by a constant

, the value of which is stored in the memory of the VD 14. Thus, at the output of the VD 14, an updated estimate of the range D _R to the target is obtained, which does not contain errors due to the movement of the target:

Since the frequency deviations of chirp pulses in odd and even sounding periods are equal in absolute value and opposite in sign, expression (4) corresponds to a delay Δt _D equal to the average value of the delays of the maximum and minimum readings of the difference signal. This explains the absence of error (3) determined by the target speed in estimate (4).

The value n _max - n _min from the output B2 13 is fed to the inputs of the VRS 15 and VND 16.

In VRS 15 of the target is the absolute value of the radial velocity of the target in accordance with the expression:

, значение которого рассчитывается предварительно, хранится в памяти ВРС 15.Constant factor

, the value of which is calculated in advance, is stored in the memory of the VRS 15.

The sign of the radial velocity is determined based on expression (3). The values of τ _and and λ are non-negative, so the sign of Δt _v is determined by the signs of the radial velocity v _R and the frequency deviation Δf.

If v _R >0 (the target is removed) and the signal has a positive frequency deviation (Δf>0), then the maximum of the compressed pulse will lag behind the delay Δt _D , which corresponds to a stationary target. The maximum compressed pulse with a negative frequency deviation (Δf<0), on the contrary, will be observed earlier than the moment Δt _D . Thus, when v _R >0, the maximum of the difference signal x _vych1 (nT) will lag relative to the minimum (n _max T > n _min T). When v _R <0 (the target is approaching), the sign of the right side of expression (3) changes to the opposite, and the maximum of the difference signal x _SC1 (nT) will be ahead of the minimum (n _max T < n _min T).

Based on the described patterns, the output of the VND 16 generates a value if the sign of the difference n _max -n _min is positive (the target is removed, v _R >0) or the value "0" if the sign of the difference n _max -n _min is negative (the target is approaching, v _R , <0).

The operation of the system (when processing chirp signals reflected from a receding target, v _R >0) is explained by the time diagrams shown in FIG. 4. On the timing diagram, the signal x _BX (t) is shown starting from the first period of radiation. The emitted chirp pulse is shown schematically for ease of understanding. From the timing diagrams it follows that after the first two probing periods at the output B1 9 in each next probing period (even and odd), signals of the same shape are generated, which makes it possible to correctly determine the direction of the target (v _R >0).

The correct functioning of the system was verified by simulation. The simulation results obtained correspond to those shown schematically in FIG. 4 and confirm that the set of known operations applied in the described invention ensures the achievement of the claimed technical results.

Thus, the described invention is a moving target selection system that provides simultaneous measurement of the range, radial velocity and direction of movement of objects in each sounding period.

Sources of information:

1. Patent 3225349 USA. Moving target indicating radar system. Appl.: 12/17/1962. Published: 12/21/1965.

2. US Patent 5,870,054. IPC G01S 13/528. Moving target indicator with no blind speeds. Appl.: 10.12.1982. Published: 09.02.1999.

3. Markovich I.I., Kopytin A.P., Maryev A.A. Digital signal processing in a radar complex using probing signals with linear frequency modulation and a changing sign of the frequency deviation // Mater. III All-Russian scientific. - those. conf. "Supercomputer technologies" (SKT-2014). - T. 2. - Rostov-on-Don: Publishing House of the Southern Federal University, 2014. - S. 235-239.

4. Markovich I.I. Algorithm for selection of moving targets with interperiod compensation of signal envelopes. Radar systems for special and civil purposes. 2013-2015 / ed. Yu.I. White. - M.: Radio engineering, 2016.

5. The system of selection of moving targets with the measurement of range, radial velocity and direction of movement: Pat. Markovich, A.A. Maryev. Applicant and patent holder - FGAOU VO "Southern Federal University". Published: 07/26/2017. Bull. No. 21.

6. Markovich I.I. Implementation of algorithms for digital formation of quadrature components in location complexes for various purposes // Bulletin of Computer Technologies - 2006.-№6 - P. 16-21.

7. Markovich I.I. Digital signal processing in systems and devices: monograph / I.I. Markovich. - Rostov n / a: Publishing house of SFU: 2012.-236 p.

8. C. Cook, M. Bernfeld. radar signals. Per. from English. ed. B.C. Kelzon. - M. Publishing House "Soviet Radio", 1971. - 568 p.

9. Trukhachev A.A. Radar signals and their applications. - M.: Military Publishing, 2005. - 320 p.

Claims (1)

A moving target selection system (MTS) with measuring range, radial velocity and direction of movement in each sounding period, containing serially connected digital quadrature components generator (DFCCS), random access memory 1 (RAM 1), matched filter (SF) with connected permanent memory device (ROM), the control input of which is connected to the control input of the SDC system, the calculator of the module (VM), the output of which is connected to the input of the random access memory device 2 (RAM 2), as well as the subtractor 1, the output of which is connected to the inputs of the time position calculators (VVP ) maximum and minimum, the adder (C), the inputs of which are connected to the outputs of the GDP of maximum and minimum, the subtractor 2 (B2), the non-inverting input of which is connected to the output of the GDP of the maximum, and the inverting input - to the output of the GDP of the minimum, the range calculator connected to the output C (VD), from the output of which an estimate of the range to the target is obtained, connected to the output B2 calc a radial velocity tester (VRS), from the output of which the value of the module of the target’s radial velocity is obtained, as well as a direction calculator (VND) connected to the output B2, from the output of which the sign of the target’s radial velocity is obtained, characterized in that a signal switch 1 (KS1) is introduced , the first and second inputs of which are connected respectively to the outputs of the VM and RAM2, the control input is connected to the control input of the ROM, and the output is connected to the non-inverting input B1, and the signal switch 2 (KS2), the first and second inputs of which are connected, respectively, to the outputs of the VM and RAM2, the control input is connected to the control input of the ROM, and the output is connected to the inverting input B1.

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