A Target Detection Method for an Anti-Interference Space-Based TDM-MIMO Radar System

Abstract

An anti-interference space-based TDM-MIMO radar system target detection method. Based on the signal model of the space-based TDM-MIMO radar system, a parametric model of the transmitted waveform is established. The composite ambiguity function of the transmitted signal set characterizing the radar detection performance and the orthogonality characterizing anti-spoofing interference are used as evaluation functions to optimize the design of the radar transmitted signal set. By successively performing signal processing such as matched filtering corresponding to each transmitted waveform on the echo signal, correcting the array walk of high-speed targets, and grouped coherent accumulation, signal processing gain is obtained, and at the same time, the signal-to-interference-plus-noise ratio is improved. On the premise of ensuring the radar detection performance, the anti-interference performance is taken into account. Moreover, the composite ambiguity function of the waveform has the characteristic of being insensitive to Doppler. When detecting high-speed moving targets, it is applicable to the actual engineering application of space-based TDM-MIMO radar for detecting high-speed space targets.

Description

Technical Field

[0001] The present invention relates to a method for detecting targets of an anti-interference space-based TDM-MIMO radar system, belonging to the field of radar technology, and further relates to the field of space debris target detection and anti-interference in space-based systems. Background Art

[0002] With the rapid development of world aerospace technology, the number of space debris generated by failed satellites, rocket bodies, discarded objects and their mutual collisions has increased sharply. Especially in recent years, with the rapid development of low-cost commercial aerospace and large-scale low-earth orbit constellations, the space debris has shown an explosive growth trend, posing a great threat to the safety of on-orbit spacecraft and human space activities. Currently, the main detection means for space debris are ground-based radars and optical systems. Compared with optical, infrared and other sensors, space-based radars have the advantages of all-weather, all-day, high-precision positioning and velocity measurement for detecting space debris; compared with ground-based radars, they can monitor targets at close range, with lower requirements and costs for power aperture, and because of the weak attenuation of electromagnetic waves in space, they can operate in very high frequency bands and use very high resolutions to depict the details of space debris. Therefore, space-based radar detection is an important development trend for future space debris detection. Currently, space powers such as the United States, Russia, France, and Canada have all carried out research and demonstration on space-based space debris monitoring radar systems. According to literature research, currently, only the space-based debris detection radar carried on the space station in the United States at home and abroad lacks public information, and these radar systems are not of the MIMO radar system.

[0003] Space-based radars have attracted great attention from domestic and foreign research institutions due to their unique advantages in detecting small space debris. Space-based radars have very broad market application prospects in future space debris detection and ensuring the flight safety of space vehicles. At the same time, in future space confrontations, space-based radars can also be used for close reconnaissance and tracking of high-threat space targets. However, since the operating orbit of space-based radars is known, relevant parameters such as radar frequency and waveform are extremely easy to be detected by enemy reconnaissance equipment, and targeted electromagnetic interference can be carried out on space-based radars by using electronic attacks. Therefore, the anti-interference performance of the system also needs to be considered.

[0004] At present, many research institutions at home and abroad have carried out relevant research on waveform design of MIMO radar systems, mainly including several implementation forms such as Frequency Division Multiplexing (FDM), Code Division Multiplexing (CDM), and Time Division Multiplexing (TDM). The TDM-MIMO radar system is commonly used in frequency modulated continuous wave radars. CDM-MIMO is commonly used in pulse radars, and orthogonal coding signals are mostly used, but there are problems such as Doppler sensitivity. The FDM-MIMO radar system is mostly used in MIMO-SAR, but it occupies a large amount of frequency band resources. Summary of the Invention

[0005] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, providing a method for target detection of an anti-jamming space-based TDM-MIMO radar system, solving the performance loss of high-speed target detection, and at the same time considering that relevant parameters such as the transmitted waveform of the space-based radar are extremely easy to be detected by the enemy's reconnaissance equipment, there is a problem of anti-spoofing jamming.

[0006] The technical solution of the present invention is: a method for target detection of an anti-jamming space-based TDM-MIMO radar system, including the following steps:

[0007] Based on the signal model of an M transmit and N receive space-based TDM-MIMO radar system, establish a parametric model of the transmitted waveform of the anti-jamming space-based TDM-MIMO radar system;

[0008] Determine the number M of orthogonal waveforms in the transmitted waveform set of the radar system and the code length P of each waveform;

[0009] Construct the transmitted waveform set of the radar signal;

[0010] Establish the mapping relationship between the transmitted pulse, the transmitting array antenna, and the transmitted signal;

[0011] M transmitting antennas transmit signals in sequence according to the established mapping relationship, and the receiving array simultaneously receives the echo signals;

[0012] For the echo data received by N array elements respectively, perform range-direction pulse compression on each of them in sequence according to the order of the transmitted waveforms using the matching filtering weights corresponding to each waveform;

[0013] Correct the movement of each array of the transmitting array relative to the target;

[0014] Group and coherently accumulate every M pulses to eliminate sidelobes and at the same time improve the signal-to-interference ratio;

[0015] Perform coherent accumulation processing on the signals of all pulses to achieve moving target detection.

[0016] Furthermore, the transmitted signal of the radar system is

[0017]

[0018] Among them, It can be expressed as:

[0019]

[0020] Among them, The f0 is the center frequency, P = BT is the code length, B and T are the bandwidth and time width of the signal respectively, and T p = T / P is the sub-pulse width, and T r is the pulse repetition period; the is the p-th symbol of the th transmitted signal; M is the number of radar transmitting array elements; N is the number of radar receiving array elements.

[0021] Furthermore, the method for determining the number M of orthogonal waveforms in the radar system transmission waveform set includes the following steps:

[0022] According to the slant range resolution ρ required by the radar r to determine the signal bandwidth B or given the signal bandwidth, satisfying the following conditions:

[0023]

[0024] where c = 3×10 8 m / s is a constant;

[0025] According to the radar system parameters, set the signal time width T and pulse repetition period T r ; the radar system parameters include radar transmission power, antenna gain, and operating range;

[0026] According to the time width T and bandwidth B of the signal, determine the preliminary code length P = BT of the signal; that is

[0027] According to the required angular resolution index Δβ, determine the number M of transmitting array elements and the number N of receiving array elements of the space-based TDM-MIMO radar, satisfying the following conditions:

[0028]

[0029] where k' = 0.886 is a constant.

[0030] Furthermore, iterate the initial sequence multiple times to construct M orthogonal codes with code length P Specifically, it includes the following steps:

[0031] (1) Solve the code length P0 of the initial sequence and the number of iterations a and b according to the formula:

[0032]

[0033] (2) Find two sequences X 0 and Y 0 with a length of P0 and a cross-correlation result of 0;

[0034] (3) Using [X 0 , Y 0 as the initial vector, perform a recursive iteration a times according to the following formula to obtain two sequences X a and Y a , (P1 = 2 a P0), where in the following formula refers to the sequence of Y a in reverse order.

[0035] [X 1 Y 1 = [X 0 Y 0 (-X 0 )Y 0

[0036] [X a Y a = [X a-1 Y a-1 (-X a-1 )Y a-1

[0037] (4) Let the initial matrix Divide F 0 into four parts, which are:

[0038]

[0039] These four parts can be expressed as is a vector of length 1×P1; Iterate once to obtain F 1 , that is, duplicate each of these four parts of F 0 to get the upper left and lower right parts of F 1 , and duplicate each of these four parts of F 0 and take the negative sign of the original part to get the upper right and lower left parts of F 1 .

[0040] Divide F 1 into four parts, expressed as

[0041]

[0042] From the 2×2P1 matrix F 0 ​​The M×P matrix F is obtained after b iterations b :

[0043]

[0044] Wherein, and (1≤i,j≤K and K = M / 2) are vectors of length 1×P / M, and their expressions are as follows:

[0045]

[0046]

[0047]

[0048]

[0049] (5) Each row vector of the M×P matrix F b is used as a set of sequence codes in the orthogonal code sequence set .

[0050] Furthermore, the cross-correlation function R and (p = 1,2,3,...,P; r,s = 1,2,...,M) between any two signals in the M transmit orthogonal waveform sets satisfies R r,s (τ) (r≠s) satisfies R r,s (0) = 0.

[0051] Furthermore, the composite ambiguity function of the M transmit waveforms {S1(t), S2(t),..., S M (t)} has the characteristics of an impulse function, and the composite ambiguity function is given by the following formula:

[0052]

[0053] Wherein, is the ambiguity function of S m (t), τ is the time delay, and f d is the Doppler frequency; when f d = 0, the composite ambiguity function is also the composite correlation function, that is, the sum function of the autocorrelation functions of all waveforms, that is, all sidelobes are zero.

[0054] Furthermore, the mapping relationship between the transmit pulse, the transmit array element antenna, and the transmit signal is:

[0055] (1) The relationship between the serial number l of the transmit pulse and the serial number m of its corresponding transmit antenna is

[0056] m = l - kk × M

[0057] where kk is an integer, 1 ≤ m ≤ M, 1 ≤ l ≤ L; L is the total number of transmitted pulses.

[0058] (2) The relationship between the sequence number l of the transmitted pulse and the sequence number of the corresponding transmitted signal is determined by the formula

[0059]

[0060] where randperm(M) represents a random permutation of M integers from 1 to M.

[0061] Furthermore, N receiving antennas receive echo signals. After down-conversion, the echo signal received by the nth (n = 1, 2,..., N) receiving antenna is expressed as:

[0062]

[0063] where the first term in the above formula represents the target echo signal, the second term is the deception interference signal, A T is the target amplitude, τ T is the target time delay, f d is the target Doppler frequency, A J is the interference amplitude, τ J is the time delay of the interference, and n0 is the noise.

[0064] A computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the steps of the method for detecting a target of an anti-jamming space-based TDM-MIMO radar system are implemented.

[0065] An anti-jamming space-based TDM-MIMO radar system target detection device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for detecting a target of an anti-jamming space-based TDM-MIMO radar system are implemented.

[0066] The advantages of the present invention compared with the prior art are as follows:

[0067] (1) A method for detecting a target of an anti-jamming space-based TDM-MIMO radar system. Based on the signal model of the space-based TDM-MIMO radar system, a parametric model for transmitting waveform design based on the composite ambiguity function and cross-correlation function is established, taking into account the anti-jamming performance while ensuring the radar detection performance.

[0068] (2) The TDM-MIMO radar signal of the target detection method proposed by the present invention is insensitive to Doppler. When detecting high-speed moving targets, it is applicable to the actual engineering application of space-based TDM-MIMO radar for detecting high-speed space targets. Description of the Drawings

[0069] Figure 1 is the processing flow chart of the target detection method of the present invention;

[0070] Figure 2 is the schematic diagram of the range ambiguity function of the transmitted signal set of the present invention;

[0071] Figure 3 is the schematic diagram of the composite range ambiguity function of the transmitted signal of the present invention under the conditions that the Doppler frequencies are 0 Hz and 600 KHz respectively;

[0072] Figure 4 is the schematic diagram of the composite ambiguity function of the transmitted signal of the present invention;

[0073] Figure 5 is the schematic diagram of the orthogonality between transmitted signal 1 and transmitted signal 3 of the present invention;

[0074] Figure 6 is the result after pulse compression processing of a single pulse echo signal;

[0075] Figure 7 The results of using receiving arrays 1, 2, and 3 of the present invention to receive echo signals after range migration correction are shown;

[0076] Figure 8 is the result after coherent integration processing after range migration correction;

[0077] Figure 9 is the moving target detection result. Detailed Implementation Modes

[0078] To better understand the above technical solutions, the technical solutions of the present application will be described in detail below with reference to the drawings and specific embodiments. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical solutions of the present application, rather than limitations on the technical solutions of the present application. Without conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.

[0079] The following further details the target detection method of an anti-interference space-based TDM-MIMO radar system provided by the embodiments of the present application with reference to the accompanying drawings of the specification. The specific implementation manners may include (such as Figures 1 to 9As shown in the figure: Based on the signal model of the space-based TDM-MIMO radar system with M transmit and N receive antennas, establish a parametric model for the transmitted waveform of the anti-jamming space-based TDM-MIMO radar system; determine the number M of orthogonal waveforms in the transmitted waveform set of the radar system and the code length P of each waveform; construct the transmitted waveform set of the radar signal; establish the mapping relationship between the transmitted pulse, the transmitting array antenna, and the transmitted signal; the M transmitting antennas transmit signals in sequence according to the established mapping relationship, and the receiving array simultaneously receives the echo signals; for the echo data received by each of the N array elements, perform range-direction pulse compression on the received echo data in sequence according to the order of the transmitted waveforms using the matching filter weights corresponding to each waveform; correct the movement of each array of the transmitting array relative to the target; perform grouped coherent integration for every M pulses to eliminate sidelobes and improve the signal-to-interference ratio at the same time; perform coherent integration processing on the signals of all pulses to achieve moving target detection.

[0080] The transmitting and receiving arrays of the radar are one-dimensional linear arrays, with M transmitting array elements and N receiving array elements, and the spacing between the transmitting array elements is d T = Nλ / 2, and the spacing between the receiving array elements is d R = λ / 2, which can be equivalently regarded as a one-dimensional M×N virtual array with an element spacing of λ / 2, where λ is the radar operating wavelength; the transmitting signal set of the radar has M orthogonal waveforms, denoted as The M transmitting antennas transmit signals in sequence according to a preset mapping relationship. Every M pulses are set as a group of pulse trains. Within a group of pulse trains, the transmitted signal of the transmitting antenna selects a waveform from the transmitting signal set of the radar for transmission, ensuring that the transmitted signals of the M transmitting antennas do not repeat; all receiving antennas simultaneously receive the echo signals; assume that there are a total of L1 groups of pulse trains, and each group of pulse trains is transmitted in sequence by the transmitting array from 1 to M, and the serial numbers of the corresponding transmitted signals are arranged in order or randomly arranged as M integers; the total number of transmitted pulses is L, that is, L = M×L1.

[0081] The preset mapping relationship mentioned above means:

[0082] 1) The relationship between the serial number l of the transmitted pulse and the serial number m of its corresponding transmitting antenna is:

[0083] m = l - kk×M

[0084] where kk is an integer, 1 ≤ m ≤ M, 1 ≤ l ≤ L;

[0085] 2) The relationship between the serial number l of the transmitted pulse and the serial number of its corresponding transmitted signal is given by the formula

[0086]

[0087] where randperm(M) represents a random permutation of M integers from 1 to M.

[0088] A method for target detection of an anti-interference space-based TDM-MIMO radar system is as follows:

[0089] (1) Based on an M transmit and N receive space-based TDM-MIMO radar system, establish a parametric model for anti-interference space-based TDM-MIMO radar waveform design. The transmitted signal of the radar system can be expressed as:

[0090]

[0091] where can be expressed as:

[0092]

[0093] where: The f0 is the center frequency, P = BT is the code length, B and T are the bandwidth and time width of the signal respectively, T p = T / P is the sub-pulse width, T r is the pulse repetition period; the is the p-th symbol of the th transmitted signal; the M is the number of radar transmitting array elements; the N is the number of radar receiving array elements;

[0094] The parametric model of the transmitted waveform set of the space-based TDM-MIMO radar system is optimized and designed for the transmitted waveform set with the composite ambiguity function of the transmitted signal set representing the radar detection performance and the orthogonality between the waveforms representing anti-spoofing interference as the evaluation function.

[0095] (2) Determine parameters such as the number M of orthogonal waveforms in the transmitted waveform set of the radar system and the code length P of each waveform;

[0096] 1) According to the required slant range resolution ρ r of the radar, determine the signal bandwidth B or given the signal bandwidth, satisfying the following conditions:

[0097]

[0098] where c = 3×10 8 m / s is a constant;

[0099] 2) Set the signal time width T and pulse repetition period T r according to system parameters such as the radar transmission power, antenna gain, and operating range;

[0100] 3) Determine the preliminary code length P = BT of the signal according to the time width T and bandwidth B of the signal; that is

[0101] 4) Determine the number of transmitting array elements \(M\) and the number of receiving array elements \(N\) of the space-based TDM-MIMO radar according to the required angular resolution index \(\Delta\beta\) (unit: radian), satisfying the following conditions:

[0102]

[0103] where \(k' = 0.886\) is a constant.

[0104] (3) Construct \(M\) orthogonal codes with code length \(P\) by iterating the initial sequence multiple times

[0105] 1) Solve for the code length \(P_0\) of the initial sequence, and the number of iterations \(a\) and \(b\) according to the formula:

[0106]

[0107] 2) Find two sequences \(X\) 0 and \(Y\) 0 with a length of \(P_0\), and require the cross-correlation result of the two sequences to be 0;

[0108] 3) Using \([X\) 0 , \(Y\) 0 as the initial vector, perform \(a\) recursive iterations according to the following formula to obtain two sequences \(X\) a and \(Y\) a with a length of \(P_1\) (\(P_1 = 2\) a \(P_0\)), where \(\) in the following formula refers to the sequence of \(Y\) a in reverse order. \([X\) 1 \(Y\) 1 = [X\) 0 \(Y\) 0 (-X\) 0 )\(Y\) 0

[0109] [X\) a \(Y\) a = [X\) a-1 \(Y\) a-1 (-X\) a-1 )\(Y\) a-1

[0110] 4) Let the initial matrix Divide \(F\) 0 into four parts, which can be written as:

[0111]

[0112] These four parts can be expressed as is a vector with a length of \(1\times P_1\). As shown in the following formula, after 1 iteration, \(F\) 1 can be obtained, that is, \(F\)​​0 These four parts are each duplicated to obtain F 1 for the upper left and lower right parts of 0 These four parts of F are each duplicated and the negative sign is taken for the original parts to obtain F 1 for the upper right and lower left parts of 1 Divide F into four parts, denoted as

[0113]

[0114] The 2×2 P1 matrix F 0 is iterated b times to obtain an M×P dimensional matrix F b :

[0115]

[0116] where and (1 ≤ i, j ≤ K and K = M / 2) are vectors of length 1×P / M, and their expressions are as shown in the following formula:

[0117]

[0118]

[0119]

[0120]

[0121] 5) Take each row vector of the M×P matrix F b as a set of sequence codes in the sequence set.

[0122] The cross-correlation function R and between any two signals r,s (τ) (r ≠ s) in the M transmit orthogonal waveform sets satisfies the requirement of R r,s (0) = 0, and the cross-correlation function is given by the following formula:

[0123]

[0124] The composite ambiguity function of the M transmit waveforms {S1(t), S2(t),..., S M (t)} has the characteristics of an impulse function, and the composite ambiguity function is given by the following formula:

[0125]

[0126] where is Sm The ambiguity function of (t), where τ is the time delay and f d is the Doppler frequency. When f d = 0, the composite ambiguity function is the composite correlation function, which is the sum function of the autocorrelation functions of all waveforms, i.e., all sidelobes are zero.

[0127] (4) Establish the mapping relationship between the transmitted pulse, the transmitting array element antenna, and the transmitted signal; M transmitting antennas transmit signals in sequence according to the established mapping relationship, and the receiving array simultaneously receives the echo signals.

[0128] (5) N receiving antennas receive the echo signals. The echo signal received by the nth (n = 1, 2, …, N) receiving antenna can be expressed as:

[0129]

[0130] where the first term in the above formula represents the target echo signal, and the second term is the deception interference signal (where is the intercepted transmitted signal). A T is the target amplitude, τ T is the target time delay, f d is the target Doppler frequency, A J is the interference amplitude, τ J is the time delay of the interference.

[0131] (6) Sequentially perform range-direction pulse compression on the L echo signals respectively received by N receiving antennas using the matched filters of their respective waveforms in the order of the transmitted waveforms, and perform FFT conversion to the frequency domain;

[0132] (7) Use methods such as keystone to correct the range walk generated by each transmitting array relative to the target;

[0133] (8) Perform coherent integration processing on the results after range walk compensation every M pulses; Since the matching function corresponds one-to-one with the jump of the transmitted signal, the energy of the target signal can be coherently integrated, while the interference signal only matches the matching function of the intercepted transmitted signal and is orthogonal to other transmitted waveforms, without obtaining a large integration gain. Therefore, the output signal-to-interference-plus-noise ratio is greatly improved after coherent integration processing; Since the composite ambiguity function of M transmitted signals has the characteristic of zero sidelobes, the influence of sidelobes is eliminated after coherent integration processing.

[0134] In the signal processing of the echo signal of the space-based TDM-MIMO radar system, the result after range migration compensation is coherently integrated every M pulses; since the matching function corresponds one-to-one with the jump of the transmitted signal, the energy of the target signal can be coherently integrated, while the interference signal only matches the matching function of the intercepted transmitted signal and is orthogonal to other transmitted waveforms, and does not obtain a large integration gain. Therefore, the output signal-to-interference-plus-noise ratio is greatly improved after the coherent integration processing, achieving the purpose of anti-interference; since the composite ambiguity function of M transmitted signals has the characteristic of zero sidelobes, the influence of the sidelobes is eliminated after the coherent integration processing.

[0135] (9) Finally, perform moving target detection on the processing result of (8).

[0136] In the solution provided in the embodiment of the present application, the usage scenario of the present invention is: a sparse transmitting array is used as the radar platform, and the spacing between transmitting array elements is d T = Nλ / 2, the spacing between receiving array elements is d R = λ / 2, the electromagnetic wave propagation speed c = 3×10 8 m / s, the relative speed between the space debris target and the TDM-MIMO radar is 5 km / s, the initial distance of the target from the radar is 25 km, the interference distance from the radar is 30 km, the signal-to-noise ratio SNR = -5 dB, the jam-to-noise ratio JNR = 15 dB, and the signal-to-interference-plus-noise ratio is -20 dB; the number of transmitted pulses L = 96.

[0137] As Figure 1 shown in the processing flow chart of the target detection method of the present invention, it can be seen from Figure 1 that a target detection method for an anti-interference space-based TDM-MIMO radar system provided by the present invention specifically includes the following implementation steps:

[0138] (1) Based on the M transmit and N receive space-based TDM-MIMO radar system, establish a parametric model for the waveform design of the anti-interference space-based TDM-MIMO radar. The transmitted signal of the radar system can be expressed as:

[0139]

[0140] where can be expressed as:

[0141]

[0142] where:

[0143] the f0 = 90 GHz is the center frequency, P = BT is the code length, B and T are the bandwidth and time width of the signal respectively, T p = T / P is the sub-pulse width, T r is the pulse repetition period; the is the p-th symbol of the th transmitted signal; M is the number of radar transmitting elements; N is the number of radar receiving elements;

[0144] (2) Determine parameters such as the number of orthogonal waveforms M in the radar system's transmitted waveform set and the code length P of each waveform;

[0145] 1) Determine the signal bandwidth B = 32 MHz according to the required slant range resolution ρ r = 5 m, satisfying the following conditions:

[0146]

[0147] where c = 3×10 8 m / s is a constant;

[0148] 2) Set the signal time width T = 5 us and the pulse repetition period T r = 0.5 ms according to system parameters such as radar transmit power;

[0149] Space debris moves at high speed. Internationally, the distance that must be maneuvered to avoid in space warfare is generally set at 1 km. To ensure that the radar detection range is greater than 1 km, the width of the transmitted pulse is required to be less than 6.67 us. Therefore, the signal time width is set to T = 5 us;

[0150] Considering that the warning distance is 50 km internationally in space warfare and the PRF corresponding to the maximum unambiguous distance of 50 km is 3000 Hz, to avoid range ambiguity, the system pulse repetition frequency is required to be less than 3000 Hz. Therefore, the PRF of the radar system is designed to be 2000 Hz, and thus the pulse repetition period is T r = 0.5 ms;

[0151] 3) Determine the preliminary code length P = BT = 160 of the signal according to the time width T and bandwidth B of the signal;

[0152] 4) Determine the number of transmitting elements M and the number of receiving elements N of the space-based TDM-MIMO radar according to the required angular resolution index Δβ = 0.174 rad (corresponding to 10°), satisfying the following conditions:

[0153]

[0154] where k' = 0.886 is a constant. Therefore, the number of transmitting elements M = 4 and the number of receiving elements N = 3 are set.

[0155] (3) Construct M orthogonal codes with code length P through multiple iterations of the initial sequence

[0156] 1) Solve for the code length \(P_0 = 20\) and the number of iterations \(a = 1\) and \(b = 1\) according to the formula:

[0157]

[0158] 2) Find two sequences \(X\) 0 and \(Y\) 0 ,

[0159] [\(X\) 0 = [+--+-+---++------++-][\(Y\) 0 = [-++------+-+++-+-++-]

[0160] The cross - correlation result of the two sequences is 0;

[0161] 3) Using \(X\) 0 and \(Y\) 0 as the initial vectors, perform \(a = 1\) recursive iteration according to the following formula to obtain two sequences \(X\) 1 and \(Y\) 1 , where \(\) in the following formula refers to the sequence of \(Y\) a arranged in reverse order.

[0162] [\(X\) 1 \(Y\) 1 = [\(X\) 0 \(Y\) 0 (-\(X\) 0 )\(Y\) 0

[0163] 4) Let the initial matrix Divide \(F\) 0 into four parts, which can be written as:

[0164]

[0165] These four parts can be expressed as is a vector of length \(1\times40\). As shown in the following formula, after 1 iteration, \(F\) 1 can be obtained, that is, duplicate each of these four parts of \(F\) 0 to get the upper - left and lower - right parts of \(F\) 1 ; duplicate each of these four parts of \(F\) 0 and take the negative of the original parts to get the upper - right and lower - left parts of \(F\) 1 1 Divide \(F\) 1 into four parts, expressed as

[0166]

[0167] 5) The \(4\times160\) matrix \(F\)1 Each row vector is used as an orthogonal code sequence set as a set of sequence codes in

[0168] (4) Establish the mapping relationship between the transmitted pulses, the 4 transmitting array elements, and the transmitted signals;

[0169] The sequence number l of the transmitted pulse is {1, 2, 3, 4,..., 128}, and the corresponding sequence number of the transmitting antenna is m = {1, 2, 3, 4, 1, 2, 3, 4,..., 1, 2, 3, 4};

[0170] Assume that the transmitted signal is sequential hopping. The sequence number l of the transmitted pulse is {1, 2, 3, 4,..., 128}, and the corresponding sequence number of the transmitted signal is

[0171] The 4 transmitting antennas transmit signals in sequence according to the pre-set mapping relationship. Every 4 pulses are set as a group of pulse trains. Within a group of pulse trains, the transmitted signal of the transmitting antenna selects a waveform from the radar's transmitted signal set for transmission, ensuring that the transmitted signals of the 4 transmitting antennas do not repeat; all receiving antennas receive the echo signals simultaneously; assume that there are a total of L1 = 32 groups of pulse trains. Each group of pulse trains is transmitted by the transmitting arrays 1 to 4 in sequence, and the corresponding sequence numbers of the transmitted signals are the sequential arrangement or random arrangement of 4 integers; the total number of transmitted pulses is L = 128.

[0172] (5) The 3 receiving antennas receive the echo signals. The echo signal received by the nth (n = 1, 2, 3) receiving antenna can be expressed as after down-conversion:

[0173]

[0174] where the first term in the above formula represents the target echo signal, and the second term is the spoofing interference signal (where is the intercepted transmitted signal). Assume SNR = -5dB and JNR = 15dB, and obtain the target amplitude A T = 0.56 and the interference amplitude A J = 5.6, the target time delay τ T = 166us, the time delay τ of the interference J = 200us, the target Doppler frequency f d = 600kHz, and n0 is Gaussian white noise with a power of 0dBW.

[0175] (6) Use the matched filters of their respective waveforms to perform range-direction pulse compression on the L echo signals received by the N receiving antennas respectively, and perform FFT conversion to the frequency domain;

[0176] (7) Use methods such as keystone to correct the range walk generated by each transmitting array relative to the target;

[0177] (8) Coherently integrate the result after range walk compensation every 4 pulses; since the matching function corresponds one-to-one with the jump of the transmitted signal, the energy of the target signal can be coherently integrated, while the interference signal only matches the matching function of the intercepted transmitted signal, is orthogonal to other transmitted waveforms, and does not obtain a large cumulative gain. Therefore, the output signal-to-interference-plus-noise ratio is greatly improved after the coherent integration process; since the composite ambiguity function of the 4 transmitted signals has the characteristic of zero sidelobes, the influence of the sidelobes is eliminated after the coherent integration process;

[0178] (9) Finally, perform moving target detection on the result of step (8).

[0179] Figure 2 The schematic diagram of the range ambiguity function of each transmitted signal of the optimized design is given. From Figure 2 it can be seen that the range ambiguity function of the transmitted signal has a certain sidelobe level. Figure 3 The schematic diagram of the composite range ambiguity function of the transmitted signal of the optimized design under the conditions of Doppler frequencies of 0 Hz and 600 kHz respectively is given. From Figure 3 it can be seen that the sidelobe level of the composite range ambiguity function is very low, almost 0. Therefore, the composite range ambiguity function of M transmitted waveforms has the characteristics of an impulse function. Figure 4 is the schematic diagram of the composite ambiguity function of the transmitted signal of the present invention; Figure 5 is the schematic diagram of the orthogonality performance between transmitted signal 1 and transmitted signal 3 of the present invention. From Figure 5 it can be seen that the orthogonality between the transmitted signals is good. Figure 6 is the result after pulse compression processing of a single pulse echo signal. From Figure 6 it can be seen that there are two peaks in the figure, and there is only one target. Therefore, one of them is a false peak, and the false peak corresponds to interference. Figure 7 The present invention uses receiving arrays 1, 2, and 3 to receive the results of the echo signals after range walk correction respectively; Figure 8 is the result of coherent integration processing after range walk correction; from Figure 8 it can be seen that there is only one peak in the figure, the false peak is suppressed, and the sidelobe level is also suppressed to a relatively low level. Therefore, it can be said that the interference signal is suppressed. Figure 9 is the moving target detection result, and it can be seen that a moving target is detected.

[0180] It can be seen from the specific embodiments of the present invention that a target detection method for an anti-jamming space-based TDM-MIMO radar system takes into account the anti-jamming performance while ensuring the radar detection performance, and the composite ambiguity function of the waveform has the characteristic of being insensitive to Doppler. When detecting high-speed moving targets, it is applicable to the actual engineering application of space-based TDM-MIMO radar for detecting high-speed space targets.

[0181] This application provides a computer-readable storage medium storing computer instructions, which, when run on a computer, cause the computer to execute Figure 1 the method described above.

[0182] Those skilled in the art should understand that the embodiments of this application can be provided as a method, a system, or a computer program product. Therefore, this application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code.

[0183] This application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of this application. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0184] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the specified functions in Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0185] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the specified functions in Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0186] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalent technologies, this application is also intended to cover these modifications and variations.

[0187] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A target detection method for an anti-interference space-based TDM-MIMO radar system, characterized in that, It includes the following steps: Based on the signal model of the M - transmit and N - receive space - based TDM - MIMO radar system, establish a parametric model of the transmit waveform of the anti - interference space - based TDM - MIMO radar system; Determine the number of orthogonal waveforms M in the transmit waveform set of the radar system and the code length P of each waveform; Construct the transmit waveform set of the radar signal; Establish the mapping relationship between the transmit pulse, the transmit array antenna, and the transmit signal; The M transmit antennas transmit signals in sequence according to the established mapping relationship, and the receive array simultaneously receives the echo signals; For the echo data received by each of the N array elements, perform range - direction pulse compression on the echo data received by each array element in sequence using the matching filter weights corresponding to each waveform according to the order of the transmit waveforms; Correct the movement generated by each array of the transmit array relative to the target; Perform grouped coherent integration for every M pulses to eliminate sidelobes and improve the signal - to - interference ratio at the same time; Perform coherent integration processing on the signals of all pulses to achieve moving target detection; Construct M orthogonal codes of length P by iterating the initial sequence multiple times Specifically, it includes the following steps: (1) Solve the code length P0 of the initial sequence, and the iteration times a and b according to the formula: (2) Find two sequences X 0 and Y 0 with length P0 and cross-correlation result of 0; (3) With [X 0 , Y 0 as the initial vector, perform a recursive iteration a times according to the following formula to obtain two sequences X a and Y a , where P1 = 2 a P0, and in the following formula refers to the sequence after reversing Y a : [X 1 Y 1 = [X 0 Y 0 (-X 0 )Y 0 ​ [X a Y a = [X a-1 Y a-1 (-X a-1 )Y a-1 ​ (4) Let the initial matrix Divide F 0 into four parts, which are: These four parts are denoted as is a vector of length 1×P1; after 1 iteration, F is obtained 1 , that is, F 0 These four parts are each copied once to obtain the upper left and lower right parts of F 1 , and for these four parts of F 0 each are copied once and the original parts are negated to obtain the upper right and lower left parts of F 1 ; for F 1 is divided into four parts, denoted as The 2×2 P1 matrix F 0 is iterated b times to obtain the M×P matrix F b : Among them, and are vectors with a length of 1×P / M, where 1≤i,j≤K and K=M / 2, and their expressions are as shown in the following formula: (5) Take each row vector of the M×P matrix F b as a set of sequence codes in the orthogonal code sequence set and Any two signals among the M transmitted orthogonal waveforms and The cross-correlation function R r,s (τ) satisfies R r,s (0) = 0, p = 1, 2, 3, ..., P; r, s = 1, 2, ..., M, r ≠ s; The composite ambiguity function of M transmitted waveforms {S1(t), S2(t),..., S M (t)} has the characteristics of an impulse function, and the composite ambiguity function is given by the following formula: Among them, is the ambiguity function of S m (t), τ is the time delay, and f d is the Doppler frequency; when f d = 0, the composite ambiguity function is also the composite correlation function, that is, the sum function of the autocorrelation functions of all waveforms, that is, all sidelobes are zero.

2. The target detection method for an anti-interference space-based TDM-MIMO radar system according to claim 1, characterized in that: The transmit signal of the radar system is Among them, is expressed as: Among them, where f0 is the center frequency, P = BT is the code length, B and T are the bandwidth and time width of the signal respectively, and T p = T / P is the sub-pulse width, and T r is the pulse repetition period; the is the p-th symbol of the th transmitted signal; M is the number of radar transmitting array elements; N is the number of radar receiving array elements.

3. A method for target detection of an anti-interference space-based TDM-MIMO radar system according to claim 1, characterized in that, The method for determining the number of orthogonal waveforms M in the transmit waveform set of the radar system includes the following steps: According to the slant range resolution ρ required by the radar r Determine the signal bandwidth B or given the signal bandwidth, satisfying the following conditions: where c = 3×10 8 m / s is a constant; Set the signal time width T and pulse repetition period T according to the radar system parameters r ; The radar system parameters include radar transmit power, antenna gain, and operating range; Determine the preliminary code length P of the signal according to the time width T and bandwidth B of the signal, i.e., P = BT; that is Determine the number of transmit array elements M and the number of receive array elements N of the space - based TDM - MIMO radar according to the required angular resolution index Δβ, satisfying the following conditions: where k′ = 0.886 is a constant.

4. A method for target detection of an anti-interference space-based TDM-MIMO radar system according to claim 1, characterized in that, The mapping relationship between the transmit pulse, the transmit array antenna, and the transmit signal is: (1) The relationship between the serial number l of the transmit pulse and the serial number m of its corresponding transmit antenna is m = l - kk×M where kk is an integer, 1 ≤ m ≤ M, 1 ≤ l ≤ L; L is the total number of transmit pulses; (2) The relationship between the serial number l of the emission pulse and the serial number of the corresponding emission signal therebetween, = 1, 2, …, M, is given by the formula Determine, where randperm(M) represents a random permutation of M integers from 1 to M.

5. A method for target detection of an anti-interference space-based TDM-MIMO radar system according to claim 1, characterized in that, The N receive antennas receive the echo signals, and the echo signal received by the nth receive antenna after down - conversion is expressed as: where n = 1, 2, …, N. The first term in the above formula represents the target echo signal, the second term is the deception jamming signal, A T is the target amplitude, τ T is the target time delay, f d is the target Doppler frequency, A J is the jamming amplitude, τ J is the time delay of the jamming, and n0 is the noise.

6. A computer-readable storage medium, the computer-readable storage medium stores a computer program, characterized in that, When the computer program is executed by a processor, it realizes the steps of the method according to any one of claims 1 to 5.

7. An anti-interference space-based TDM-MIMO radar system target detection device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, it realizes the steps of the method according to any one of claims 1 to 5.

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