RU2562614C1 - Method of simulating radar targets - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method of simulating radar targets, based on receiving, by a relay station, probing signals of a space synthetic-aperture radar station s_p(t), amplifying said signals, shifting the carrier frequency f₀ to an intermediate frequency f_if, filtering, analogue-to-digital conversion with a sampling interval δτ, recording the obtained sequence of digital samples s_pi=s_p((i-1)δτ), filtering, amplifying the relayed radar signals and emission thereof towards the space synthetic-aperture radar station, further specifying the number of false marks N formed on the radar image, vectors of geocentric coordinates of points on the earth's surface corresponding to the position of the n-th false mark x_fn=[x_fn,y_fn,z_fn], where $$n=\overline{\mathrm{1,}N},$$

and the amplitude transfer coefficient of the signal of the n-th false mark a_n∈[0;1], calculating for each p-th probing the current distance between the space synthetic-aperture radar station and each of the N points on the earth's surface, corresponding to the position of the false marks R_{l pn}, and the distance between the space synthetic-aperture radar station and the relay station R_rp, specifying the pulse modulation law in the form of a sequence of digital samples of the mark at the p-th probing, reading the i-th sample of the p-th probing pulse s_pi through a time interval τ_r, multiplying said sample with the corresponding reading of the modulating frequency M_pi, converting the obtained sequence of digital samples of the products s_piM_pi into an analogue relayed pulse and shifting its frequency from the intermediate frequency f_if to the carrier frequency f₀.

EFFECT: low probability of correct detection of masked objects with space synthetic-aperture radar.

2 dwg

Description

The invention relates to the field of radio engineering, in particular, to methods and techniques for radio-electronic suppression of space radar with a synthesized aperture of the antenna (PCA).

There is a method of simulating radar targets, which consists in the re-reflection of a radar signal incident on an object at the operating frequency of a space SAR in the direction opposite to the direction of incidence using angle reflectors [see, for example, Vakin S.A., Shustov L.N. Fundamentals of radio countermeasures and electronic intelligence. - M .: Soviet Radio, 1968, p. 321-326; Paly A.I. Electronic warfare. - M .: Military Publishing House, 1989, p. 90-99] or Luneberg lenses [see, for example, Theoretical Foundations of Radar / Ed. POISON. Shirmana - Textbook for universities. - M .: Soviet Radio, 1970, p. 80-81].

However, this method only works effectively in a relatively narrow sector of the angles of incidence of the probing signal of the space SAR and provides the formation of only single marks of false targets in the radar image (XRD).

There is also a method for simulating radar targets used in the operation of SARs for their radiometric and geometric calibration [see, for example, Radar systems for air reconnaissance, decoding of radar images / Ed. L.A. School. - M.: Publishing. VVIA them. prof. NOT. Zhukovsky, 2008, p. 318-320]. It consists in simulating radar targets by receiving, amplifying and re-emitting a radar signal while maintaining its coherence with a calibration transponder [see, for example, Airborne reconnaissance radar systems, decoding of radar images / Ed. L.A. School. - M.: Publishing. VVIA them. prof. NOT. Zhukovsky, 2008, p. 318-320].

The disadvantage of this method is that it allows you to get only a single target mark on the radar, formed by the space SAR. From this it follows that with the radio suppression of space SAR by simulating radar targets with a limited number of calibration transponders, the number of simulated radar targets on the radar can be insufficient to mask images of real objects whose linear dimensions exceed the corresponding resolution elements of the space SAR.

; Р=T_s/T_и; T_s и Т_и - временной интервал синтезирования апертуры антенны и период следования зондирующих импульсов соответственно; t - текущее время, их усилении, переносе несущей частоты импульсов f₀ на промежуточную частоту f_пч, фильтрации, аналого-цифровом преобразовании с интервалом дискретизации δτ, записи полученной последовательности цифровых отсчетов s_pi=s_p((i-1)δτ), где $$i=\overline{\mathrm{1,}{N}_{отсч}}$$

; $$N_{отсч}=\frac{{\tau }_{и}}{\delta \tau }$$

- количество цифровых отсчетов p-го зондирующего импульса; τ_и - длительность импульса, считывании отсчетов s_pi, их цифро-аналоговом преобразовании, переносе восстановленного таким образом сигнала с промежуточной частоты f_пч на несущую частоту f₀, фильтрации, амплитудно-фазовой модуляции импульсов в интересах изменения времени задержки от импульса к импульсу для уводящих по дальности помех или изменения значения доплеровского сдвига частоты от импульса к импульсу для уводящих по скорости помех, усилении полученных радиолокационных сигналов и их излучении в направлении космической РСА [см., например, Радиоэлектронная борьба. Цифровое запоминание и воспроизведение радиосигналов и электромагнитных волн / Под ред. А.И. Куприянова. - М.: Вузовская книга, 2009, с. 221-274].The closest in essence and the achieved result (prototype) to the claimed method of simulating radar targets is the method of creating false target marks on radar, based on the reception by the repeater of the probe pulses of space SAR s _p (t), where $$p=\overline{\mathrm{one,}P}$$

; P = T _s / T _and ; T _s and T _and - the time interval for synthesizing the aperture of the antenna and the repetition period of the probe pulses, respectively; t is the current time, their amplification, transfer of the carrier frequency of the pulses f ₀ to the intermediate frequency f _pch , filtering, analog-to-digital conversion with a sampling interval δτ, recording the obtained sequence of digital samples s _pi = s _p ((i-1) δτ), Where $$i=\overline{\mathrm{one,}{N}_{\mathrm{about}t\mathrm{from}h}}$$

; $$N_{\mathrm{about}t\mathrm{from}h}=\frac{{\tau }_{\mathrm{and}}}{\delta \tau }$$

- the number of digital samples of the p-th probe pulse; τ _and are the pulse duration, reading the samples s _pi , their digital-to-analog conversion, transferring the signal thus restored from the intermediate frequency f _pc to the carrier frequency f ₀ , filtering, amplitude-phase modulation of pulses in the interest of changing the delay time from pulse to pulse for leading along the distance of interference or changes in the value of the Doppler frequency shift from pulse to pulse for leading along the speed of interference, amplification of received radar signals and their radiation in the direction of space SAR [see, Example, Electronic warfare. Digital storing and reproduction of radio signals and electromagnetic waves / Ed. A.I. Kupriyanova. - M.: University Book, 2009, p. 221-274].

The disadvantages of the prototype are the radiation in response to each probe pulse of a space SAR only one relayed pulse (one mark of a false target on the radar) and the lack of consideration in the law of amplitude-phase modulation of the change in the current distance between the space SAR and the simulated object.

The technical result of the invention is expressed in reducing the probability of correct detection of masked objects by space SAR.

, и амплитудный коэффициент передачи сигнала n-й ложной отметки a _n∈[0;1], вычисляют для каждого p-го зондирования текущее расстояние между космической РСА и каждой из N точек на земной поверхности, соответствующих положению ложных отметок R_{л pn} и расстояние между космической РСА и ретранслятором R_{r p}, задают закон модуляции импульсов (модулирующую функцию) в виде последовательности цифровых отсчетов:The technical result is achieved by the fact that in the known method of simulating radar targets, based on the reception by the repeater of the probe pulses of space SARs s _p (t), their amplification, transfer of the carrier frequency f ₀ to the intermediate frequency f _pc , filtering, analog-to-digital conversion with a sampling interval δτ, recording the received digital sequence samples _{s pi = s p ((i} - 1) δτ), filtering, amplification retransmitted radar signals and their radiation towards the PCA space, further define the number of forming x RLI on false marks N, the vectors geocentric coordinates of the Earth's surface points corresponding to the position n-th mark false _ln x = [x _ln, y _ln, z _ln] where $$n=\overline{\mathrm{one,}N}$$

, and the amplitude coefficient of signal transmission of the nth false mark a _n ∈ [0; 1], for each p-th sounding, calculate the current distance between the space SAR and each of the N points on the earth’s surface corresponding to the position of the false marks R _{l pn} and the distance between the space SAR and the relay R _rp , set the law of pulse modulation (modulating function) in the form of a sequence of digital samples:

,

,

- амплитуда сигнала n-й ложной отметки на p-м зондировании; $$j=\sqrt{-1}$$

- мнимая единица; G_pca и G_r - коэффициенты усиления приемопередающих антенн космической РСА и ретранслятора соответственно; Θ(Δε_p, Δβ_p) - нормированная диаграмма направленности космической РСА по мощности; Δε_p и Δβ_p - рассогласование между осью диаграммы направленности антенны космической РСА и направлением на ретранслятор по углу места и азимуту соответственно; Р_рса - мощность излучаемого космической РСА зондирующего импульса; K_r - коэффициент передачи ретранслятора, определяемый как отношение мощности зондирующего импульса космической РСА на входе его приемника к мощности импульса на выходе передатчика ретранслятора; b_и - скорость линейного изменения частоты в пределах зондирующего импульса;

- длительность временной задержки в ретрансляторе; c=3·10⁸ м/с - скорость света в свободном пространстве; τ_r - длительность процесса обработки зондирующего импульса РСА в ретрансляторе; λ - длина волны зондирующего сигнала космической РСА, считывают i-й отсчет p-го зондирующего импульса s_pi через интервал времени τ_r, умножают его на соответствующий отсчет модулирующей функции M_pi, преобразуют полученную последовательность цифровых отсчетов произведений s_piM_pi в аналоговый ретранслируемый импульс и переносят его частоту с промежуточной f_пч на несущую f₀.Where

- the amplitude of the signal of the n-th false mark on the p-th sounding; $$j=\sqrt{-\mathrm{one}}$$

- imaginary unit; G _pca and G _r are the gain of the transmitting and receiving antennas of the space SAR and the relay, respectively; Θ (Δε _p , Δβ _p ) is the normalized radiation pattern of space SAR in power; Δε _p and Δβ _p - the mismatch between the axis of the antenna pattern of the space SAR and the direction to the repeater in elevation and azimuth, respectively; Р _Рса - power of the radiated space SAR sounding pulse; K _r is the transmission coefficient of the repeater, defined as the ratio of the power of the probe pulse of the space SAR at the input of its receiver to the power of the pulse at the output of the transmitter of the repeater; b _and - the rate of linear change in frequency within the probe pulse;

- the duration of the time delay in the repeater; c = 3 · 10 ⁸ m / s is the speed of light in free space; τ _r is the duration of the processing process of the probe pulse of the SAR in the repeater; λ is the wavelength of the probe signal of the space SAR, read the i-th sample of the p-th probe pulse s _pi through the time interval τ _r , multiply it by the corresponding sample of the modulating function M _pi , convert the resulting sequence of digital samples of the products s _pi M _pi into an analog relay pulse and transfer its frequency from the intermediate f _pch to the carrier f ₀ .

The invention consists in the following. A radar station with a synthesized aperture of the antenna generates object marks on the radar image due to a Doppler frequency shift proportional to the deviation of the object azimuth relative to the center of the viewing area in the corresponding range resolution element [see, for example, G. Kondratenkov, A.Yu. Frolov Radio vision. Earth Remote Sensing Radar Systems: Textbook for High Schools / Ed. G.S. Kondratenkova. - M .: Radio engineering, 2005, p. 135-1591:

where φ (t) is the component of the total phase Φ (t) of the received radar signal with a carrier frequency f ₀ , which varies in time according to a quadratic law; t is the current time; V is the speed of the artificial Earth satellite (carrier of space SAR); θ _n is the observation angle determined by the view of the SAR space; θ is the angle corresponding to the true azimuthal position of the observed object relative to the center of the viewing area of the space SAR.

то выражение доплеровского сдвига частоты примет вид:If PCA is used in side view

then the expression of the Doppler frequency shift will take the form:

Further, assuming that the angle θ is small (such that sinθ≈θ), formula (2) can be rewritten in the final form:

Then, a deliberate change in the Doppler frequency shift by modulating the probe pulse and relaying the received pulse in the direction of the space SAR will additionally generate a false mark on the radar image with an azimuth different from the azimuth of the observed object. The necessary range resolution element can be selected by changing the delay time of the relayed pulse relative to the received probe. Thus, the radiation in the direction of the space SAR of N relayed pulses with different values of the delay time and Doppler frequency shift will ensure the formation of N false targets marks on the radar.

.As a rule, modern space SARs use radio pulses with linear frequency modulation as probing signals. A feature of the coordinated reception (compression) of such signals, implemented in all SARs, is the time offset (delay) of the output (compressed) pulse of the matched filter by a value proportional to the offset of the carrier frequency of the received pulse relative to the carrier frequency of the emitted. So, the offset of the carrier frequency f ₀ by Δf determines the delay of the compressed pulse equal to

.

This makes it possible to simultaneously enter into the parameters of the p-th relay pulse information both on the delay time (in the form of an additional offset of its carrier frequency) and on the Doppler frequency shift using additional modulation of the p-probe pulse according to a given law.

A method for simulating radar targets can be implemented using a device whose structural diagram is shown in FIG. one.

The circuit consists of a receiving antenna 1, a first amplifier 2, a reference generator 3, a first mixer 4, a data input device 5, a first filter 6, a first storage device 7, an analog-to-digital converter 8, a control device 9, a second storage device 10, a multiplier 11 , a block of calculators 12, including a distance calculator R _rp and R _{l pn} 12.1, a signal amplitude calculator of the nth false mark on the pth sounding A _pn 12.2, a delay time calculator _{tz pn} 12.3 and a modulator function _sampler M _pi 12.4, a digital analog a transducer 13, a second mixer 14, a second filter 15, a second amplifier 16, and a transmit antenna 17 connected as shown in FIG. one.

The receiving antenna 1 is designed to perform the operation of converting the incident electromagnetic waves of the ES of the space SAR into electrical signals associated with the transmission line (feeder). The first amplifier 2 provides amplification of the received probe pulses of the space SAR to the level necessary for the operation of the first mixer 4. The reference generator 3 generates a signal with a frequency f _oc = f ₀ -f _pch , required to transfer the frequency of the probe pulses of the space SAR from the carrier f ₀ to the intermediate f _pch and vice versa. In the first mixer 4, signals of the total and difference frequencies f ₀ + (f ₀ -f _pch ) = 2f ₀ -f _pch and f ₀ - (f ₀ -f _pch ) = f _pch, respectively, are formed. The data input device 5 is used to manually or automatically enter the parameters necessary for calculating the readings of the modulating function M _pi (the number of false marks N generated on the radar, the geocentric coordinates of the earth’s surface points corresponding to the position of the nth false mark x _ln = [x _ln , y _ln , z _ln ], the amplitude coefficient of signal transmission of the nth false mark a _n ∈ [0; 1], the parameters of the functioning of the space SAR are T _s , Т _и , τ _и , λ, b _и , G _pca , _Рса , normalized radiation pattern of the antenna of the space SAR Θ (ε, β), where and β - respectively elevation and azimuth vector geocentric coordinate space SAR when p-th sensing _{x p = [x p, y} p, z p], vector geocentric coordinate space XRD view area center x _Θp = [x _Θp, y _Θp , z _Θp ], the functioning parameters of the repeater are G _r , K _r , τ _r , δτ and the geocentric coordinate vector of the repeater x _r = [x _r , y _r , z _r ]). The first filter 6 selects the difference frequency signal f ₀ - (f ₀ -f _pch ), corresponding to the intermediate frequency f _pch , with the required frequency band Δf _1ph . In the first storage device 7, data on all entered parameters is stored in digital form. An analog-to-digital converter 8 is necessary for converting the p-th analog pulse coming from the output of the first filter 6 into a sequence of digital samples s _pi with a sampling interval δτ. The control device 9 is designed to control the processes of recording and reading digital samples s _pi . In the second storage device 10, data on all samples of the pth probing pulse s _{pi is} stored in digital form. The multiplier 11 performs the procedure of multiplying the i-th sample of the p-th probe pulse and the corresponding sample of the modulating function, i.e. s _pi M _pi . The block of calculators 12 is necessary for implementing the procedures for calculating the law of pulse modulation (modulating function) in the form of a sequence of digital samples:

The digital-to-analog converter 13 restores the analog signal, which is a relayed pulse, from its digital samples s _pi M _pi . In the second mixer 14, signals of total and difference frequencies f _pc + (f ₀ -f _pc ) = f ₀ and f _pc - (f ₀ -f _pc ) = 2f _pc -f _0, respectively, are _generated . The second filter 15 selects the signal of the total frequency f _pch + (f ₀ -f _pch ) corresponding to the carrier frequency f ₀ with the required frequency band Δf _2ph . The second amplifier 16 provides amplification of the relayed pulses to the required level. The transmitting antenna 17 converts the electrical signals associated with the transmission line (feeder) coming from the output of the second amplifier 16 into electromagnetic waves that propagate freely in the direction of the space SAR.

The scheme works as follows. The probe pulse of the space SAR on the p-th probe s _p (t) is received by the receiving antenna 1, amplified by the first amplifier 2 and fed to the first input of the first mixer 4. The signal of the reference generator 3 is received at the second input of the first mixer 4. As a result, the output of the first mixer 4, the signals of the total and difference frequencies f ₀ + (f ₀ -f _pch ) = 2f ₀ -f _pch and f ₀ - (f ₀ -f _pch ) = f _pch, respectively, are formed. Next, the difference signal of the intermediate frequency f _pch is extracted by the first filter 6, having a passband Δf _1ph , and fed to the input of the analog-to-digital converter 8, where it is converted into a sequence of digital samples s _pi with a sampling interval δτ, i.e. s _pi = s _p ((i-1) δτ). The obtained digital samples of the pth probe pulse s _{pi are} sequentially recorded in the second memory 10 by the recording signal received at its second input from the first output of the control device 9. After a time interval equal to the duration of the processing of the probe pulse PCA in the relay δτ, to the third input of the second memory 10 from the second control unit 9 outputs the readout signal is supplied, whereby the digital samples s _pi sequentially read and supplied to a first input ne emnozhitelya 11. The first storage device 7 via the data entry device 5 are recorded data on the number of radar images formed on the false marks N, the position vector of n-th mark false _ln x = [x _ln, y _ln, z _ln] amplitude transmission coefficient of the nth false mark a _n ∈ [0; 1], the parameters of the functioning of the space SAR — T _s , T _and , τ _and , λ, b _and , G _pca , Р _Рса , normalized radiation pattern of the antenna of the space SAR Θ (ε, β ) vector geocentric coordinate space at the time of the PCA p-th sensing _{x p = [x p, y} p, z p], geocentric coordinate vector tse tra FOV space SAR _{x Θp = [x Θp, y} Θp, z Θp], the parameters of the repeater operation _{- G r, K r, τ} r, δτ and vector geocentric coordinates repeater _{x r = [x r, y} r, z r ]. At the same time, signals containing information are generated in the first memory device 7, which has eighteen information outputs: on the first and second outputs - on time intervals T _s and T _and , on the third output - on the number of false marks N generated on the radar, on the fourth, the fifth and sixth outputs - on the vectors x _p , x _ln and x _r, respectively, at the seventh and eighth outputs - on the gain of transmitting and receiving antennas of the space SAR G _pca and the relay G _r, respectively, on the ninth output - on the amplitude transmission coefficient of the signal n false about label a _n ∈ [0; 1], in the tenth outlet - of the vector x _Θp, the eleventh outlet - of the normalized antenna pattern space XRD Θ (ε, β), the twelfth, thirteenth, fourteenth, fifteenth, sixteenth, seventeenth and eighteenth outputs - about the values of P _rsa , K _r , τ _r , τ _and , δτ, b _and and λ, respectively. In the distance calculator R _rp and R _{l pn} 12.1 upon receipt of its first, second, third, fourth, fifth and sixth signal inputs from the corresponding information outputs of the first storage device 7, the following mathematical procedures are implemented:

In this case, digital signals proportional to the values of R _rp and R _{l pn} are formed at the first and second outputs of the distance calculator R _rp and R _{l pn} 12.1, respectively.

A signal amplitude calculator of the n-th false mark on the p-th probe A _pn 12.2 when it arrives at its first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh and twelfth data inputs from the first, second, the third, seventh, eighth, ninth, fourth, sixth, tenth, eleventh, twelfth and thirteenth information outputs of the first storage device 7, respectively, as well as when the signal amplitude is received at the thirteenth input of the calculator of the nth false mark on the pth sensing A _pn 12 .2 the signal from the first output of the distance calculator R _rp and R _{l pn} 12.1 performs calculations in accordance with the analytical expression:

R _З = 6371 km - reduced radius of the Earth; h _c - satellite height from space SAR on board;

The signal proportional to the amplitudes of the false marks (6), from the output of the calculator of the amplitude of the signal of the nth false mark on the r-th sounding A _pn 12.2, goes to the sixth input of the calculator of the modulating function M _pi 12.4.

The calculator of the delay time t _{s pn} 12.3 upon receipt at its first, second, third and fourth inputs of signals from the first, second, third and fourteenth information outputs of the first storage device 7, respectively, and to the fifth and sixth inputs - signals from the first and second outputs distance calculator R _p and R _pn 12.1, respectively, performs calculations in accordance with the expression:

The output signal of the delay time calculator t _{З pn} 12.3, proportional to (7), is fed to the seventh input of the sample calculator of the modulating function M _pi 12.4. In addition, the signals from the fifteenth, sixteenth, first, second, third, seventeenth and eighteenth information outputs of the first storage device 7 are received at the first, second, third, fourth, fifth, eighth and ninth inputs of the sample calculator of the modulating function M _pi 12.4 to the tenth and eleventh inputs - signals from the first and second outputs of the distance calculator R _p and R _pn 12.1, respectively. As a result of the implementation in the computer of readings of the modulating function M _pi 12.4 of the mathematical procedure:

a digital signal is generated at its output, which is proportional to the count of the modulating function, which is fed to the second input of the multiplier 11, in which the count of the product s _pi M _{pi is} calculated. A digital signal proportional to s _pi M _pi is fed to the input of the digital-to-analog converter 13, where the analog signal representing the p-th relay pulse is restored from the samples s _pi M _pi . This pulse is supplied to the first input of mixer 14. The mixer 14, to the second input of which the signal of the reference generator 3 is supplied, generates at its output signals of total and difference frequencies f _pc + (f ₀ -f _pc ) = f ₀ and f _pc - (f ₀ -f _pch ) = 2f _pch -f _0, respectively. The total carrier frequency signal f ₀ is allocated by the second filter 15, having a passband Δf _2ph , and fed to the input of the second amplifier 16, where it is amplified to the required level. The relay pulse thus formed from the output of the second amplifier 16 is fed to the input of the transmitting antenna 17 for radiation in the direction of the space SAR.

The reduction in the probability of correct detection of masked objects by space SAR is explained as follows.

Let the space SAR form one mark of the true point target on the radar image. Using the prototype method on the radar image obtained in the space SAR, the formation of one false mark of the point target is ensured by the creation of a repeater that leads away in range or speed of interference. The simplest approach to determining the probability of the correct detection of one true target in the case under consideration allows us to obtain a specific value of the specified probability equal to

for the prototype, where N _io and N _lo - the number of true and false marks of targets, respectively.

(фиг.2) получаем для одной истинной точечной цели:

In the case of the implementation of the proposed method of simulating radar targets at $$N=N_{l\mathrm{about}}^{*}=8$$

(figure 2) we obtain for one true point target:

Thus, it is obvious that the proposed method for simulating radar targets reduces the probability of correct target detection compared to the prototype from 0.50 to 0.11.

, и амплитудный коэффициент передачи сигнала n-й ложной отметки a _n∈[0;1], вычисляют для каждого p-го зондирования текущее расстояние между космической РСА и каждой из N точек на земной поверхности, соответствующих положению ложных отметок R_{л pn} и расстояние между космической РСА и ретранслятором R_{r p}, задают закон модуляции импульсов (модулирующую функцию) в виде последовательности цифровых отсчетов:The proposed technical solution is new, because from publicly available information there is no known method for simulating radar targets, which differs from the known method based on the reception by the repeater of the probe pulses of space SAR s _p (t), their amplification, transfer of the carrier frequency f ₀ to the intermediate frequency f _pch , filtering, analog-to-digital conversion with a sampling interval δτ, recording the resulting sequence of digital samples s _pi = s _p ((i-1) δτ), filtering, amplification of relayed radar signals and their radiation in the direction of the space SAR by the fact that they additionally specify the number of false marks N formed on the radar, the vectors of the geocentric coordinates of the Earth’s surface points corresponding to the position of the nth false mark x _ln = [x _ln , y _ln , z _ln ], where $$n=\overline{\mathrm{one,}N}$$

, and the amplitude coefficient of signal transmission of the nth false mark a _n ∈ [0; 1], for each p-th sounding, calculate the current distance between the space SAR and each of the N points on the earth’s surface corresponding to the position of the false marks R _{l pn} and the distance between the space SAR and the relay R _rp , set the law of pulse modulation (modulating function) in the form of a sequence of digital samples:

Where

- амплитуда сигнала n-й ложной отметки на p-м зондировании; $$j=\sqrt{-1}$$

- мнимая единица; G_pca и G_r - коэффициенты усиления приемопередающих антенн космической РСА и ретранслятора соответственно; Θ(Δε_p, Δβ_p) - нормированная диаграмма направленности космической РСА по мощности; Δε_p и Δβ_р - рассогласование между осью диаграммы направленности антенны космической РСА и направлением на ретранслятор по углу места и азимуту соответственно; P_pca - мощность излучаемого космической РСА зондирующего импульса; K_r - коэффициент передачи ретранслятора, определяемый как отношение мощности зондирующего импульса космической РСА на входе его приемника к мощности импульса на выходе передатчика ретранслятора; b_и - скорость линейного изменения частоты в пределах зондирующего импульса;

- длительность временной задержки в ретрансляторе; c=3·10⁸ м/с - скорость света в свободном пространстве; τ_r - длительность процесса обработки зондирующего импульса РСА в ретрансляторе; λ - длина волны зондирующего сигнала космической РСА, считывают i-й отсчет p-го зондирующего импульса s_pi через интервал времени τ_r, умножают его на соответствующий отсчет модулирующей функции M_pi, преобразуют полученную последовательность цифровых отсчетов произведений s_piM_pi в аналоговый ретранслируемый импульс и переносят его частоту с промежуточной f_пч на несущую f₀.

- the amplitude of the signal of the n-th false mark on the p-th sounding; $$j=\sqrt{-\mathrm{one}}$$

- imaginary unit; G _pca and G _r are the gain of the transmitting and receiving antennas of the space SAR and the relay, respectively; Θ (Δε _p , Δβ _p ) is the normalized radiation pattern of space SAR in power; Δε _p and Δβ _p - the mismatch between the axis of the antenna pattern of the space SAR and the direction to the repeater in elevation and azimuth, respectively; P _pca is the power of the radiated space SAR sounding pulse; K _r is the transmission coefficient of the repeater, defined as the ratio of the power of the probe pulse of the space SAR at the input of its receiver to the power of the pulse at the output of the transmitter of the repeater; b _and - the rate of linear change in frequency within the probe pulse;

- the duration of the time delay in the repeater; c = 3 · 10 ⁸ m / s is the speed of light in free space; τ _r is the duration of the processing process of the probe pulse of the SAR in the repeater; λ is the wavelength of the probe signal of the space SAR, read the i-th sample of the p-th probe pulse s _pi through the time interval τ _r , multiply it by the corresponding sample of the modulating function M _pi , convert the resulting sequence of digital samples of the products s _pi M _pi into an analog relay pulse and transfer its frequency from the intermediate f _pch to the carrier f ₀ .

The proposed technical solution has an inventive step, since it does not explicitly follow from published scientific data and known technical solutions that the method of simulating radar targets can reduce the likelihood of correct detection of probed objects.

The proposed technical solution of the proposed method for simulating radar targets is industrially applicable, since it can be implemented on the basis of standard devices - antennas [see, for example, Kocherzhevsky G.N. Antenna feeder devices. - M .: Communication, 1972; Handbook of Radar / Ed. M. Skolnik, New York, 1970: Per. from English (in four volumes) / Under the general ed. K.N. Trofimov; Volume 2. Radar antenna devices. - M .: Owls. radio, 1979], devices for recording and reproducing signals [see, for example, Electronic warfare. Digital storing and reproduction of radio signals and electromagnetic waves / Ed. A.I. Kupriyanova. - M.: University Book, 2009, p. 221-274]. At the same time, from the structure of signal recording and reproducing devices, designs, for example, receiving and transmitting antennas 1 and 17, first and second amplifiers 2 and 16, reference generator 3, first and second mixers 4 and 14, first and second filters 6, and 15, analog-to-digital converter 8, control device 9, second storage device 10, and digital-to-analog converter 13.

For the implementation of the data input device 5, the first storage device 7, the multiplier 11 and the block of calculators 12 can be used personal computers (PCs) [see, for example, S. Simonovich et al. Big book of a personal computer. - M .: OLMA Media Group, 2007]. Moreover, as a data input device 5, you can use a standard PC keyboard and a mouse-type manipulator [see, for example, S. Simonovich et al. Big book of a personal computer. - M .: OLMA Media Group, 2007], and the first storage device 7, a multiplier 11 and a block of calculators 12 can be implemented in software. In addition, the first storage device 7 can also be performed using standard operational or permanent storage devices [Ugryumov EP Digital circuitry: Textbook. manual for universities. / E.P. Gloomies. - 2nd ed., Revised. and additional - St. Petersburg: BHV-Petersburg, 2005, p. 227-343], and the multiplier 11 - according to the schemes of matrix multipliers [Ugryumov EP Digital circuitry: Textbook. manual for universities. / E.P. Gloomies. - 2nd ed., Revised. and additional - St. Petersburg: BHV-Petersburg, 2005, p. 132-138].

Claims (1)

A method for simulating radar targets, which consists in receiving by the repeater a probe pulse of a space radar station with a synthesized antenna aperture (PCA) s _p (t), where

P = T _s / T _and ; T _s and T _and - the time interval for synthesizing the aperture of the antenna and the repetition period of the probe pulses, respectively; t is the current time, their amplification, transfer of the carrier frequency f ₀ to the intermediate frequency f _pch , filtering, analog-to-digital conversion with a sampling interval δτ, recording the obtained sequence of digital samples

Where

- the number of digital samples of the p-th probe pulse; τ _and are the pulse duration, filtering, amplification of the relayed radar signals and their radiation in the direction of the space SAR, characterized in that they additionally specify the number of false marks N formed on the radar image, the geocentric coordinates of the earth’s surface points corresponding to the position of the nth false mark

Where

and amplitude coefficient of signal transmission of the n-th false mark

calculate for each p-th sounding the current distance between the space SAR and each of the N points on the earth’s surface corresponding to the position of the false marks R _{l pn} and the distance between the space SAR and the relay R _rp , set the pulse modulation law (modulating function) in the form of a sequence of digital counts:

Where

- the amplitude of the signal of the n-th false mark on the p-th sounding;

- imaginary unit; G _pca and G _r are the gain of the transmitting and receiving antennas of the space SAR and the relay, respectively;

- normalized radiation pattern of space SAR in power; Δε _p and Δβ _p - the mismatch between the axis of the antenna pattern of the space SAR and the direction to the repeater in elevation and azimuth, respectively; P _pca is the power of the radiated space SAR sounding pulse; K _r is the transmission coefficient of the repeater, defined as the ratio of the power of the probe pulse of the space SAR at the input of its receiver to the power of the pulse at the output of the transmitter of the repeater; b _and - the rate of linear change in frequency within the probe pulse;

- the duration of the time delay in the repeater, s = 3 · 10 ⁸ m / s is the speed of light in free space; τ _r is the duration of the processing process of the probe pulse of the SAR in the repeater; λ is the wavelength of the probe signal of the space SAR, read the i-th sample of the p-th probe pulse s _pi through the time interval τ _r , multiply it by the corresponding sample of the modulating function M _pi , convert the resulting sequence of digital samples of the products s _pi M _pi into an analog relay pulse and transfer its frequency from the intermediate f _pch to the carrier f ₀ .

Images