A spaceborne probing radar transmitting signal determining, transmitting and range ambiguous echo separating receiving device

Abstract

The application belongs to the technical field of radar, and particularly relates to a satellite-borne detection radar transmitting signal determination, transmission and distance ambiguous echo separation receiving equipment, comprising the following steps: S1: determining the pulse repetition frequency of the transmitting signal; S2: initializing the orthogonal phase encoding linear frequency modulation signal; S3: optimizing the design of the orthogonal phase encoding linear frequency modulation signal; S4: transmitting the optimized orthogonal phase encoding linear frequency modulation signal; and S5: receiving the echo equipment. Through the optimization of multiple groups of pulse repetition frequencies and multiple groups of orthogonal encoding linear frequency modulation signals, the satellite-borne moving target detection radar repetition frequency selection and automatic separation receiving of arbitrary distance ambiguous echoes can be adaptively realized, so that better moving target detection performance is obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of radar, and further relates to a satellite-borne detection radar transmitting signal determination, transmission and range ambiguous echo separation receiving device. The present application can be used for transmitting and receiving signals of a satellite-borne moving target detection radar system. BACKGROUND

[0002] Satellite-borne radars play an important role in cross-border surveillance, and important battlefield information is obtained through the detection of moving targets. The detection range of space-based radars reaches thousands of kilometers. When the repetition frequency of radar transmitted pulses is too high, the time delay of echo signals in the observation band may exceed the pulse interval, so that the echo signals of the previous transmitted pulse and the echo signals of the currently transmitted pulse overlap together, thereby causing range ambiguity. When monitoring the ground moving targets, it is necessary to suppress clutter signals to improve the detection performance of moving targets. However, the serious range ambiguous echo not only deteriorates the clutter suppression performance, but also causes inaccurate distance parameter estimation of moving targets.

[0003] 1. After searching, it is found that the Chinese invention with the announcement number CN 117239418A "Satellite-borne radar two-dimensional beam scanning control method and device" discloses a satellite-borne radar two-dimensional beam scanning control method, which determines the radar parameter setting and data storage mode in the radar two-dimensional beam scanning process, but does not optimize the design of the transmitted signal, and there is a problem that the echo range ambiguity limits the detection performance of moving targets;

[0004] 2. After searching, it is found that the Chinese invention with the announcement number CN202311524805.1 "Satellite-borne SAR range ambiguity suppression method based on transmit-receive pointing separation" discloses a satellite-borne SAR range ambiguity suppression method based on transmit-receive pointing separation. Through the separation of the transmit-receive pattern pointing in the distance direction of the antenna, the width of the main lobe of the pattern is reduced, the first ambiguous region is moved outside the main lobe of the antenna, and thus the range ambiguity is suppressed. This method needs a large elevation antenna aperture to obtain a narrow antenna main lobe, which has a relatively high cost, and greatly reduces the radar antenna scanning data rate;

[0005] 3. A high-repetition frequency coded synthetic aperture radar real-time echo recovery method was found by searching the Chinese invention "A high-repetition frequency coded synthetic aperture radar real-time echo recovery method" with the announcement CN 117239418A. The patent document discloses a high-repetition frequency coded synthetic aperture radar real-time echo recovery method. By constructing a phase encoding sequence with a period, the transmitted pulse is phase encoded in the slow time domain in the radar transmit link. At the radar receiving end, the received echo data is grouped. Then, a phase encoding guide matrix is constructed, and an echo recovery weight vector is derived through the phase encoding guide matrix. Finally, the real-time and accurate multi-sub-mapping band unambiguous signal recovery is realized by the fuzzy signal fast recovery algorithm disclosed in the invention. This method mainly designs the waveform for the space-borne synthetic aperture radar system, and does not involve the range ambiguity problem of ground clutter, and does not consider the influence of range ambiguity on clutter suppression and moving target detection performance;

[0006] 4. A space-borne synthetic aperture radar range ambiguity suppression method was found by searching the Chinese invention "A space-borne synthetic aperture radar range ambiguity suppression method" with the announcement CN202011449362.0. The patent document discloses a space-borne synthetic aperture radar range ambiguity suppression method. For the two aspects of signal system and signal processing of space-borne SAR system, linear frequency modulation signals are transmitted by using positive and negative frequency modulation slopes, and the received signals are compressed twice: the first distance compression is matched filtering for the ambiguous area target, and the main energy in the ambiguous area is filtered out and then inverted to the time domain echo; the second distance compression is matched filtering for the main lobe area target and subsequent azimuth compression, and two-dimensional focusing imaging is completed, which can effectively weaken the interference of the main ambiguous area target signal to the main lobe area target. However, this method can only suppress the first distance ambiguity clutter, and loses its effect in the case of multiple distance ambiguities.

[0007] In summary, in order to overcome the lack of systematic consideration and response method for the range ambiguity problem of space-borne moving target detection radar in the prior art, a space-borne detection radar transmitting signal determination, transmission and range ambiguity echo separation receiving device is proposed. SUMMARY

[0008] The purpose of the present application is to overcome the shortcomings of the prior art, and to design a space-borne detection radar transmitting signal determination, transmission and range ambiguity echo separation receiving device, which can adaptively realize the range ambiguity echo separation of space-borne moving target detection radar, so as to obtain better moving target detection performance.

[0009] The technical scheme adopted by the present application is as follows:

[0010] A space-borne detection radar transmitting signal determination, transmission and range ambiguity echo separation receiving device, comprising the following steps:

[0011] S1: determining the pulse repetition frequency of the transmitted signal;

[0012] S2: initializing the orthogonal phase coded linear frequency modulation signal;

[0013] S3: optimizing the design of the orthogonal phase coded linear frequency modulation signal;

[0014] S4: transmitting the optimized orthogonal phase coded linear frequency modulation signal;

[0015] S5: receiving the echo device outputting multiple frequency multi-channel multi-unambiguous range echo data.

[0016] The step S1 comprises the following steps:

[0017] S11: predicting the maximum Doppler frequency of the target of interest according to the following formula

[0018]

[0019] In the formula, f d represents the maximum Doppler frequency of the target of interest, V r represents the speed of the target of interest, and λ represents the wavelength of the radar;

[0020] S12: predicting the Doppler spectrum width caused by the motion of the spaceborne platform according to the following formula

[0021]

[0022] In the formula, B0 represents the Doppler spectrum width caused by the motion of the spaceborne platform, V a represents the speed of the spaceborne platform along the track direction, α0 represents the central azimuth angle of the radar antenna beam, θ0 represents the central elevation angle of the antenna beam, and α1 represents the width of the main lobe of the antenna beam.

[0023] S13: setting the first group of pulse repetition frequencies as F0=f d +B0;

[0024] S14: calculating the range ambiguity number according to the first group of pulse repetition frequencies F0 according to the following formula

[0025]

[0026] In the formula, M represents the range ambiguity number, represents the floor operation, R1 represents the maximum slant range, R2 represents the nearest slant range, and c represents the speed of light.

[0027] S15: calculating the maximum pulse repetition frequency of the range ambiguity number M according to the following formula

[0028]

[0029] S16: selecting the pulse repetition frequency F maxM groups of non-repeated pulse repetition frequencies are arbitrarily selected within the range of [Fmin, Fmax], and are recorded in ascending order as F1, F2, …, F M ;

[0030] S17: Determine that the transmitting signal adopts M+1 groups of pulse repetition frequencies, respectively F0, F1, F2, …, F M .

[0031] The step S2 includes the following steps:

[0032] S21: Determine the parameter m according to the following formula

[0033]

[0034] Wherein, max[] represents taking the maximum value, β represents the pulse duty cycle, F s represents the fast time sampling frequency, N c represents the phase encoding spread spectrum number.

[0035] S22: The code length of the orthogonal polyphase code is set as L=2 m-1 ;

[0036] S23: Calculate the m-th layer Hadamard sequence according to the following formula

[0037]

[0038] Wherein, W m represents the m-th layer Hadamard sequence, m represents the number of layers of the Hadamard sequence, the 0-th layer Hadamard sequence is recorded as W0=[1], and W m-1 represents the m-1-th layer Hadamard sequence. The specific form of the m-th layer Hadamard sequence can be obtained by recursive calculation according to the above formula.

[0039] S24: Construct the orthogonal quadrature phase code matrix of the m-th layer Hadamard sequence according to the following formula

[0040]

[0041] Wherein, C0(m) represents the orthogonal quadrature phase code matrix of the m-th layer Hadamard sequence, m represents the number of layers of the Hadamard sequence, the dimension of the matrix C0(m) is L, and j represents the imaginary unit, and (-j) 2 =1.

[0042] S25: Take each row of the orthogonal quadrature phase code matrix of the m-th layer Hadamard sequence as a group of initial orthogonal polyphase code sequences, and L groups of initial orthogonal polyphase code sequences can be obtained, recorded as c1, c2, …, c L Each group of initial orthogonal polyphase code sequences contains L elements.

[0043] S26: Spread spectrum processing is performed on the lth group of orthogonal polyphase code sequences according to the following formula

[0044]

[0045] wherein, denotes the lth group of spread spectrum orthogonal polyphase code sequences, cl l denotes the lth group of initial orthogonal polyphase code sequences, l denotes a serial number, l e {1, 2, …, L}, N c denotes a spread spectrum number.

[0046] S27: The lth group of orthogonal phase-coded linear frequency modulation signals is generated according to the following formula

[0047]

[0048] wherein, x l,i denotes the lth group of orthogonal phase-coded linear frequency modulation signals at the ith moment, denotes a rectangular signal, and T p denotes a pulse width, exp() denotes an exponential with a natural number e as a base, f denotes a radar carrier frequency, k r denotes a frequency modulation rate of a linear frequency modulation signal, t i = ixt0 denotes the ith moment, t0 denotes a fast time sampling interval, i e {1, 2, …, N r}, N r denotes a number of fast time samples, and N r = LxN c , denotes the lth element of the lth group of spread spectrum orthogonal polyphase code sequences , l denotes a serial number, l e {1, 2, …, L}.

[0049] L groups of spread spectrum orthogonal polyphase code sequences can be used to generate L groups of orthogonal phase-coded linear frequency modulation signals, which are denoted as b1, b2, …, b L , respectively. Each group of orthogonal phase-coded linear frequency modulation signals contains N r sub-signals, i.e.

[0050] The step S3 includes the following steps:

[0051] S31: The L groups of orthogonal phase-coded linear frequency modulation signals are respectively taken as initial populations, and L initial populations can be obtained, each of which contains N r sub-signals.

[0052] S32: The average delay cross-correlation value d l

[0053]

[0054] wherein || denotes a modulo value, ∑ denotes a summation operation, p denotes a population sequence number, l denotes a population sequence number, i denotes a sub-signal sequence number, b l,i denotes the i-th sub-signal of the l-th initial population, l ∈ {1, 2, …, L}, i ∈ {1, 2, …, N r}, H denotes a conjugate transpose.

[0055] S33: Calculate the fitness of the l-th population according to the following formula

[0056]

[0057] wherein a l denotes the fitness of the l-th population, l denotes a population sequence number, l ∈ {1, 2, …, L}, d l denotes the average time-delay cross-correlation value of the l-th population with other populations, h denotes an average time-delay cross-correlation bandwidth.

[0058] S34: Arrange L groups of populations in ascending order of fitness to obtain a population set Ω, and perform cross and mutation operations on the populations in Ω except the first M+1 groups of populations.

[0059] S35: Calculate the average fitness of the first M+1 groups of populations in Ω according to the following formula

[0060]

[0061] wherein γ denotes the average fitness of the first M+1 groups of populations in Ω.

[0062] S36: If the average fitness γ of the first M+1 groups of populations in Ω is greater than a set fitness threshold η γ , repeat steps S34 to S35 until γ ≤ η γ , stop iteration, and η γ denotes a set fitness threshold.

[0063] S37: Take the first M+1 groups of populations in Ω as M+1 groups of optimally designed orthogonal phase-coded linear frequency modulation signals, denoted as s1, s2, …, s M+1 , s l denotes the l-th group of optimally designed orthogonal phase-coded linear frequency modulation signals, l ∈ {1, 2, …, M+1}.

[0064] The step S4 comprises the following steps:

[0065] S41: A space-borne moving target detection radar system is installed with N antennas along a flight path direction, and M+1 groups of pulse repetition frequency signals are sequentially transmitted using the full aperture of the antennas.

[0066] S42: Each group of pulse repetition frequency signals contains K pulses, and M+1 optimally designed orthogonal phase coded linear frequency modulation signals are alternately transmitted between the K pulses;

[0067] The step S5 includes the following steps:

[0068] S51: The receiving echo device receives echoes by using N antennas of the radar system respectively to obtain N channel echo signals, each of which contains M+1 groups of echo signals with different pulse repetition frequencies, and each group of echo signals with different pulse repetition frequencies contains K pulse signals;

[0069] S52: For the echo signals of the same group of pulse repetition frequencies, the receiving echo device separates the echo signals of each pulse of each channel by using fast time dimension matching filtering processing according to the following formula:

[0070]

[0071] wherein y q,n,k,l represents the lth separated signal of the kth pulse of the nth channel of the qth group of pulse repetition frequencies, y q,n,k represents the echo signal of the kth pulse of the nth channel of the qth group of pulse repetition frequencies, represents convolution operation, * represents conjugate operation, q ∈ {1, 2, …, M+1}, n ∈ {1, 2, …, N}, k ∈ {1, 2, …, K}, l ∈ {1, 2, …, M+1}.

[0072] S53: For the echo signals of each pulse of each channel of the same group of pulse repetition frequencies, M+1 groups of orthogonal phase coded linear frequency modulation signals s1, s2, …, s M+1 are respectively used to obtain M+1 separated signals according to the operation of step S52;

[0073] S54: Under the same group of pulse repetition frequencies, the receiving echo device combines the lth rangeless echo data of the nth channel according to the following formula:

[0074]

[0075] wherein, represents the lth rangeless echo data of the nth channel of the qth group of pulse repetition frequencies, and the parameters y q,n,k,l represents the lth separated signal of the kth pulse of the nth channel of the qth group of pulse repetition frequencies, q ∈ {1, 2, …, M+1}, n ∈ {1, 2, …, N}, k ∈ {1, 2, …, K}.

[0076] S55: for the nth channel of the qth group of pulse repetition frequencies, according to step S54, traversing l, l element of {1, 2, …, M+1}, M+1 kinds of range ambiguity echo data of the nth channel of the qth group of pulse repetition frequencies can be obtained, denoted as The lth range ambiguity echo data of the nth channel of the qth group of pulse repetition frequencies contains K pulse signals, q element of {1, 2, …, M+1}, n element of {1, 2, …, N}, l element of {1, 2, …, M+1};

[0077] S56: traversing M+1 groups of pulse repetition frequencies and N channels, receiving M+1 kinds of range ambiguity echo data of M+1 groups of pulse repetition frequencies and N channels output by the echo device.

[0078] The steps S1-S5 are tested in a simulation experiment environment by using simulation data.

[0079] The technical effects achieved by the present application are as follows:

[0080] The satellite-borne detection radar signal determination, transmission and range ambiguity echo separation receiving device provided by the present application can overcome the inaccuracy of dynamic target parameter estimation caused by range ambiguity and Doppler ambiguity of echo signals of the existing satellite-borne radar, and has the ability to separate the range ambiguity and Doppler ambiguity of multiple frequency target signals, thereby improving the accuracy of dynamic target detection of the satellite-borne radar.

[0081] The satellite-borne detection radar signal determination, transmission and range ambiguity echo separation receiving device provided by the present application can solve the problem of separating arbitrary range ambiguity echo, and can overcome the deterioration of clutter suppression performance caused by range ambiguity of echo signals of the existing satellite-borne radar, thereby effectively improving the dynamic target detection performance of the satellite-borne radar in engineering practice. BRIEF DESCRIPTION OF DRAWINGS

[0082] Figure 1 is a flowchart of the satellite-borne detection radar signal determination, transmission and range ambiguity echo separation receiving device provided by the present application;

[0083] Figure 2 The delay cross-correlation performance of arbitrary two groups of optimized orthogonal phase-coded linear frequency modulation signals is given.

[0084] Figure 3 The clutter suppression output signal-to-noise ratio of the method of the present application is given. DETAILED DESCRIPTION

[0085] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0086] Example 1:

[0087] like Figure 1 As shown, a receiving device for determining, transmitting, and separating range ambiguity echoes from a spaceborne detection radar signal includes the following steps:

[0088] S1: Determine the pulse repetition frequency of the transmitted signal;

[0089] S11: Predict the maximum Doppler frequency of the target of interest according to the following formula.

[0090]

[0091] In the formula, f d V represents the maximum Doppler frequency of a sensory target. r λ represents the speed of the target of interest, and λ represents the radar operating wavelength.

[0092] S12: Predict the Doppler spectral width caused by the motion of the spaceborne platform according to the following formula.

[0093]

[0094] In the formula, B0 represents the Doppler spectral width caused by the motion of the spacecraft platform, and V a α0 represents the speed of the spaceborne platform along the flight path, θ0 represents the azimuth angle of the radar antenna beam center, θ0 represents the elevation angle of the antenna beam center, and α1 represents the width of the antenna beam main lobe.

[0095] S13: Set the repetition frequency of the first pulse group to F0 = f d +B0;

[0096] S14: Calculate the number of distance ambiguities based on the first group of pulse repetition frequency F0 using the following formula.

[0097]

[0098] In the formula, M represents the number of distance ambiguities. This indicates a round-down operation, R1 represents the maximum slant distance, R2 represents the nearest slant distance, and c represents the speed of light;

[0099] S15: Calculate the maximum pulse repetition frequency with distance ambiguity M according to the following formula.

[0100]

[0101] S16: selecting M groups of non-repeated pulse repetition frequencies in the range greater than F0 and less than F max ; M ;

[0102] S17: determining that the transmitting signal adopts M+1 groups of pulse repetition frequencies, respectively F0, F1, F2, …, F M .

[0103] S2: initializing a quadrature phase encoding linear frequency modulation signal;

[0104] S21: determining a parameter m according to the following formula

[0105]

[0106] wherein max[] represents taking the maximum value, β represents a pulse duty cycle, F s represents a fast time sampling frequency, N c represents a phase encoding spread spectrum number.

[0107] S22: setting a code length of the quadrature polyphase code as L=2 m-1 ;

[0108] S23: calculating an mth layer Hadamard sequence according to the following formula

[0109]

[0110] wherein W m represents the mth layer Hadamard sequence, m represents a layer number of the Hadamard sequence, the 0th layer Hadamard sequence is represented as W0=[1], and W m-1 represents an (m-1)th layer Hadamard sequence. The specific form of the mth layer Hadamard sequence can be obtained by recursive calculation according to the above formula.

[0111] S24: constructing a quadrature four-phase code matrix of the mth layer Hadamard sequence according to the following formula

[0112]

[0113] wherein C0(m) represents the quadrature four-phase code matrix of the mth layer Hadamard sequence, m represents a layer number of the Hadamard sequence, the dimension of the matrix C0(m) is L, and j represents an imaginary unit, wherein (-j) 2 =1.

[0114] S25: taking each row of the quadrature four-phase code matrix of the mth layer Hadamard sequence as a group of initial quadrature polyphase code sequences, so that L groups of initial quadrature polyphase code sequences can be obtained, which are represented as c1, c2, …, c Leach group of initial orthogonal polyphase code sequences contains L elements.

[0115] S26: spread spectrum processing is performed on the lth group of orthogonal polyphase code sequences according to the following formula

[0116]

[0117] wherein, denotes the lth group of spread spectrum orthogonal polyphase code sequences, cl l denotes the lth group of initial orthogonal polyphase code sequences, l denotes a serial number, l ∈ {1, 2, …, L}, N c denotes a spread spectrum number.

[0118] S27: the lth group of orthogonal phase-coded linear frequency modulation signals is generated according to the following formula

[0119]

[0120] wherein, x l,i denotes the lth group of orthogonal phase-coded linear frequency modulation signals at the ith moment, T p denotes a pulse width, t i denotes the ith moment, t i = i × t0, t0 denotes a fast time sampling interval, i ∈ {1, 2, …, N r}, N r denotes a total number of fast time samples, N r = L × N c , denotes a rectangular signal, f exp() denotes an exponential with a natural number e as a base, f denotes a radar carrier frequency, k r denotes a frequency modulation rate of a linear frequency modulation signal, denotes the lth element of the lth group of spread spectrum orthogonal polyphase code sequences , l denotes a group serial number of a spread spectrum orthogonal polyphase code sequence, l ∈ {1, 2, …, L}.

[0121] L groups of orthogonal phase-coded linear frequency modulation signals can be generated by using L groups of spread spectrum orthogonal polyphase code sequences, which are denoted as b1, b2, …, b L each group of orthogonal phase-coded linear frequency modulation signals contains N r sub-signals, i.e.

[0122] S3: the orthogonal phase-coded linear frequency modulation signal is optimized and designed;

[0123] S31: L groups of orthogonal phase-coded linear frequency modulation signals are respectively taken as initial populations, L initial populations can be obtained, and each initial population contains N r sub-signals.

[0124] S32: Calculate the average delay cross-correlation value d of the lth population with other populations according to the following formula l

[0125]

[0126] wherein || represents the modulo value, ∑ represents the summation operation, p represents the population serial number, l represents the population serial number, i represents the sub-signal serial number, b l,i represents the ith sub-signal of the lth initial population, l ∈ {1, 2, …, L}, i ∈ {1, 2, …, N r}, H represents the conjugate transpose.

[0127] S33: Calculate the fitness of the lth population according to the following formula

[0128]

[0129] wherein a l represents the fitness of the lth population, l represents the population serial number, l ∈ {1, 2, …, L}, d l represents the average delay cross-correlation value of the lth population with other populations, h represents the average delay cross-correlation bandwidth.

[0130] S34: Arrange the L groups of populations in ascending order of fitness to obtain a population set Ω, and remove the first M+1 populations from Ω, and perform crossover and mutation operations on the remaining populations.

[0131] S35: Calculate the average fitness of the first M+1 populations in Ω according to the following formula

[0132]

[0133] wherein γ represents the average fitness of the first M+1 populations in Ω.

[0134] S36: If the average fitness γ of the first M+1 populations in Ω is greater than the set fitness threshold η γ , repeat steps S34 to S35 until γ ≤ η γ , then stop iteration, η γ represents the set fitness threshold.

[0135] S37: Take the first M+1 populations in Ω as the M+1 groups of orthogonal phase-coded linear frequency modulation signals of the optimization design, denoted as s1, s2, …, s M+1 , s l represents the lth group of orthogonal phase-coded linear frequency modulation signals of the optimization design, l ∈ {1, 2, …, M+1}.

[0136] S4: Transmit the optimized orthogonal phase-coded linear frequency modulation signal;

[0137] S41: The space-borne moving target detection radar system installs N antennas along the track direction, and uses the full aperture of the antennas to sequentially transmit M+1 groups of pulse repetition frequency signals;

[0138] S42: Each group of pulse repetition frequency signals contains K pulses, and M+1 groups of optimally designed orthogonal phase-coded linear frequency modulation signals are alternately transmitted between the K pulses;

[0139] S5: The receiving echo device outputs multiple-frequency multi-channel multi-ambiguity-free echo data;

[0140] S51: The receiving echo device receives echoes using the N antennas of the radar system respectively, and obtains N-channel echo signals, each of which contains M+1 groups of echo signals of different pulse repetition frequencies, and each group of echo signals of different pulse repetition frequencies contains K pulse signals;

[0141] S52: For the same group of echo signals of different pulse repetition frequencies, the receiving echo device separates the echo signal of each pulse of each channel using fast-time dimension matched filtering processing according to the following formula:

[0142]

[0143] wherein y q,n,k,l represents the lth separated signal of the kth pulse of the nth channel of the qth group of pulse repetition frequencies, y q,n,k represents the echo signal of the kth pulse of the nth channel of the qth group of pulse repetition frequencies, represents convolution operation, s l represents the lth group of orthogonal phase-coded linear frequency modulation signals, * represents conjugate operation, q ∈ {1, 2, …, M+1}, n ∈ {1, 2, …, N}, k ∈ {1, 2, …, K}, and l ∈ {1, 2, …, M+1}.

[0144] S53: For the echo signal of each pulse of each channel of the same group of pulse repetition frequencies, M+1 groups of orthogonal phase-coded linear frequency modulation signals s1, s2, …, s M+1 are used respectively, and M+1 kinds of separated signals can be obtained according to the operation of step S52;

[0145] S54: Under the qth group of pulse repetition frequencies, the receiving echo device combines the lth ambiguity-free echo data of the nth channel according to the following formula:

[0146]

[0147] wherein, represents the lth ambiguity-free echo data of the nth channel of the qth group of pulse repetition frequencies, and the parameters y q,n,k,l Let l represent the l-th separation signal of the k-th pulse in the n-th channel, where q∈{1,2,…,M+1}, n∈{1,2,…,N}, and k∈{1,2,…,K}.

[0148] S55: For the nth channel of the qth pulse repetition frequency group, following step S54, traversing l, l∈{1,2,…,M+1}, we can obtain M+1 kinds of distance-free ambiguity echo data for the nth channel of the qth pulse repetition frequency group, denoted as… This represents the l-th type of distance-free ambiguity echo data of the n-th channel at the q-th pulse repetition frequency group. It contains K pulse signals, q∈{1,2,…,M+1}, n∈{1,2,…,N}, l∈{1,2,…,M+1};

[0149] S56: Traverse M+1 groups of pulse repetition frequencies and N channels respectively, and receive the echo device outputting M+1 groups of pulse repetition frequencies, N channels, and M+1 types of distance-free ambiguity echo data.

[0150] In summary, because this invention designs multiple sets of pulse repetition frequencies, multiple sets of orthogonally coded linear frequency modulated signals, signal transmission methods, and receiving equipment, it solves the problem of ambiguity in the echo range of spaceborne radar and improves the moving target detection performance of spaceborne radar.

[0151] Example 1:

[0152] like Figures 2-3 As shown, the satellite-borne detection radar signal determination, transmission, and range ambiguity echo separation receiving device given in Embodiment 1 needs to be tested in a simulation environment, as detailed below:

[0153] 1. Simulation conditions:

[0154] The simulation environment for this invention is: MATLAB R2021a, Intel(R) Core(TM) 2 Duo CPU 16GHz, Windows Professional Edition.

[0155] 2. Simulation content and result analysis:

[0156] The effectiveness of the algorithm was verified using simulation data.

[0157] Simulation verification, radar signal bandwidth is 10MHz, carrier frequency is 10GHz, the speed of the space platform is 7900m / s, the antenna azimuth size is 30 meters, which is divided into 8 channels, the current wave position antenna pointing azimuth angle and elevation angle are 89.9° and 65° respectively, the elevation beam covers 80km, the maximum speed of the target of interest is 120m / s, the half main lobe width of the antenna is 0.0286° (the deviation angle of the first zero point from the beam center),

[0158] According to the above parameters, the first group of pulse repetition frequency is set to 8500Hz, the distance ambiguity number is 4 times, five groups of pulse repetition frequencies are set, which are 8500Hz, 9000Hz, 10000Hz, 11000Hz and 12500Hz; based on 2-layer Hadamard sequence, 8 groups of orthogonal coded signals can be initialized, and after genetic algorithm optimization, 5 groups of optimized orthogonal phase coded linear frequency modulation signals are obtained. 3-level sea state is used as the observation scene, the sample screening method is used to obtain the clutter suppression processing weight coefficient, and the traditional linear frequency modulation signal is used as a comparison to verify the effectiveness of the application.

[0159] Figure 2 The delay cross-correlation performance of any two groups of optimized orthogonal phase coded linear frequency modulation signals is given, Figure 3 The clutter suppression output signal-to-clutter noise ratio of the method of the application is given, Figure 2 , Figure 3 And from the clutter suppression result, compared with the traditional "LFM" signal, the "LFM orthogonal coded signal" designed by the application can significantly improve the clutter suppression performance, significantly improve the output signal-to-clutter noise ratio for the same radial velocity of the moving target, and has better moving target detection performance.

[0160] The above only describes the preferred embodiments of the application, and it should be pointed out that for ordinary skilled persons in the art, without departing from the principles of the application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the application. The structures, devices and operation methods not specifically described and explained in the application, such as without special description and limitation, are implemented according to the conventional means in the art.

Claims

1. A space-borne surveillance radar transmit signal determination, transmission and range ambiguous echo separation reception method, characterized by: The method comprises the following steps: S1: determining the pulse repetition frequency of the transmitted signal; S2: initializing the orthogonal phase coded linear frequency modulation signal; S3: optimizing the design of the orthogonal phase coded linear frequency modulation signal; S4: transmitting the optimized orthogonal phase coded linear frequency modulation signal; S5: receiving the echo device outputting multiple frequency multi-channel multi-ambiguity echo data; The step S1 comprises the following steps: S11: predicting the maximum Doppler frequency of the target of interest according to the following formula: wherein represents the maximum Doppler frequency of the target of interest, represents the speed of the target of interest, represents the radar operating wavelength; S12: predicting the Doppler spectrum width caused by the motion of the space-borne platform according to the following formula: wherein denotes the Doppler spectrum width caused by the motion of the spaceborne platform, denotes the velocity of the spaceborne platform along the track direction, denotes the azimuth angle of the center of the radar antenna beam, denotes the elevation angle of the center of the antenna beam, denotes the width of the main lobe of the antenna beam; S13: set the first group of pulse repetition frequencies to: ; S14: According to the first group of pulse repetition frequencies The distance ambiguity number is calculated according to the following formula: wherein denotes the distance blur order, denotes a floor operation, denotes the maximum slant distance, denotes the nearest slant distance, denotes the speed of light; S15: Calculate the distance ambiguity number as the maximum pulse repetition frequency: S16: in the range of greater than while less than arbitrarily chosen non-repeating pulse repetition frequencies, in ascending order, denoted as ; S17: determine that the transmission signal adopts group pulse repetition frequency, respectively, ; The step S5 comprises the following steps: S51: receiving echoes with a radar system one antenna each to obtain a channel echo signal, each channel echo signal comprising a set of echo signals of different pulse repetition frequencies, each set of echo signals of different pulse repetition frequencies comprising one pulse signal; S52: for the echo signals of the same group of pulse repetition frequencies, the receiving echo device separates the echo signal of each pulse of each channel according to the following formula by using fast time dimension matched filtering processing: wherein, represents the group of pulse repetition frequencies the channel the pulse, a separated signal, represents the group of pulse repetition frequencies the channel the pulse, represents a convolution operation, represents a conjugate operation, , , , ; S53: for each echo signal of each pulse of each channel of the same group of pulse repetition frequencies, respectively use group orthogonal phase encoding linear frequency modulation signal , according to step S52, a kind of separated signal can be obtained signal; S54: At the same pulse repetition frequency, the receiving echo device combines the first kind of non-range ambiguous echo data of the first channel according to the following formula: ​​ wherein represents the group of pulse repetition frequencies the channel of the kind of range-free ambiguous echo data, parameters , represents the group of pulse repetition frequencies the channel the pulse of the kind of separated signal, , , ; S55: for the first group of pulse repetition frequencies, the first channel is traversed according to step S54, , , and the first group of pulse repetition frequencies, the first channel can obtain kinds of range-ambiguous echo data, denoted as , , where m represents the first group of pulse repetition frequencies, the first channel, and n represents the first kind of range-ambiguous echo data, containing pulse signals, , , ; S56: iterate group pulse repetition frequency and channel, receive echo device output group pulse repetition frequency channel a distance ambiguity free echo data.

2. The method of claim 1, wherein: the transmitted signal is a chirp signal; the transmitted signal is transmitted from a satellite; the transmitted signal is received by a satellite-based probe radar; and the transmitted signal is received by a satellite-based probe radar. The step S2 comprises the following steps: S21 : Determine parameters according to the following formula : wherein, denotes taking the maximum value, denotes the pulse duty cycle, denotes the fast time sampling frequency, denotes the phase encoding spread number; S22: The code length of the orthogonal polyphase code is set to ; S23: Calculate the first Hadamard sequence: wherein, denotes the 0th Hadamard sequence, denotes the number of layers of the Hadamard sequence, the 0th Hadamard sequence is denoted as denotes the 0th Hadamard sequence, the specific form of the 1st Hadamard sequence can be obtained by recursive calculation according to the above formula; S24: The first matrix is constructed according to the following formula Orthogonal four-phase code matrix of Hadamard sequence wherein represents the number of layers of the Hadamard sequence, represents the orthogonal four-phase code matrix of the Hadamard sequence, represents the number of layers of the Hadamard sequence, the matrix has a dimension of , represents the imaginary unit, and has ; S25: the first Each row of the orthogonal four-phase code matrix of the Hadamard sequence is taken as a group of initial orthogonal multi-phase code sequences, and The group of initial orthogonal multi-phase code sequences is denoted as Each group of initial orthogonal multi-phase code sequences contains elements. S26: spread the first data stream by a group orthogonal multi-phase code sequence according to the following formula: S26: spread the first data stream by a group orthogonal multi-phase code sequence according to the following formula: wherein, denotes the group of spreading orthogonal multiphase code sequences, denotes the group of initial orthogonal multiphase code sequences, denotes the ordinal number, , denotes the spreading number; S27: The first Group orthogonal phase-coded linear frequency modulated signal: wherein represents the th orthogonal phase-coded linear frequency modulation signal at the th time instant, represents a rectangular signal, , represents a pulse width, represents an exponential with base a natural number, , represents a radar carrier frequency, represents a frequency modulation rate of the linear frequency modulation signal, represents the th time instant, represents a fast time sampling interval, , represents a number of fast time samples, , represents the th element of the th set of spread spectrum orthogonal polyphase code sequences, , represents an ordinal number, ; Utilizing A set of spread spectrum orthogonal polyphase code sequences can be generated A set of orthogonal phase encoded linear frequency modulated signals, respectively denoted as Each set of orthogonal phase encoded linear frequency modulated signals contains sub-signals, i.e. , .

3. The method of claim 1, wherein: the transmitted signal is a chirp signal; the transmitted signal is transmitted from a satellite; the transmitted signal is received by a satellite-based probe radar; and the transmitted signal is received by a satellite-based probe radar. The step S3 comprises the following steps: S31: obtaining The group orthogonal phase encoding linear frequency modulation signal is taken as an initial population, and initial populations, each of which contains sub-signals; S32: Calculate the average delay cross-correlation value of the i-th population with other populations according to the following formula : 1 - (1 - |Ri|) / 100 : wherein, denotes a modulo value, denotes a summation operation, denotes a population order, denotes a population order, denotes a sub-signal order, denotes the th sub-signal of the th initial population, , , denotes a conjugate transpose; S33: Calculate the fitness of the i-th population according to the following formula: Fitness = 1 / (1 + f(i)) wherein, represents the fitness of the th population, represents the population order number, , represents the average delay cross-correlation value of the th population and other populations, represents the average delay cross-correlation bandwidth; S34: obtaining the population set The populations are arranged in ascending order of fitness to obtain a population set In the step S32, the first population is removed from the population set The remaining populations are subjected to crossover and mutation operations The remaining populations are subjected to crossover and mutation operations S35: Calculate according to the following formula mid-fore Mean fitness of the population: wherein represents mid-fore the mean fitness of the population; S36: If the mean fitness of the population is greater than a set fitness threshold then repeat steps S34 to S35 until the mean fitness of the population is greater than a set fitness threshold then stop iteration, denotes the set fitness threshold: S37: obtaining middle population as the optimization design group orthogonal phase-coded linear frequency modulation signal, denoted as , represent the first group of optimization design orthogonal phase-coded linear frequency modulation signal, .

4. The method of claim 1, wherein: the transmitted signal is a chirp signal; the transmitted signal is transmitted from a satellite; the transmitted signal is received by a satellite-based probe radar; and the transmitted signal is received by a satellite-based probe radar. The step S4 comprises the following steps: S41: The spaceborne moving target detection radar system is installed along the track direction adopts antenna full aperture to transmit group pulse repetition frequency signals; S42: Each set of pulse repetition frequency signals comprises pulses, which are alternately transmitted between optimally designed orthogonal phase-coded linear frequency modulated signals.

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