A method for multi-channel coherent accumulation and sidelobe suppression in dual-base MIMO radar

Abstract

This invention discloses a method for multi-channel coherent accumulation and sidelobe suppression in bistatic MIMO radar, applied in the field of radar technology. It addresses the problems of high computational complexity and accumulation sidelobes in multi-channel accumulation methods based on ergonomic search (ES). First, this invention utilizes Radon-Fourier Transform (RFT) to complete signal accumulation within a channel, and designs a fast multi-channel coherent accumulation method based on the geometric topology between the bistatic MIMO radar and the target. Second, it designs an accumulation sidelobe suppression method. By analyzing the main lobe and sidelobe distribution characteristics of the multi-channel accumulation output, a main lobe energy window function is designed to retain the main lobe energy in the multi-channel accumulation output, and the accumulation sidelobe energy is suppressed based on the point spread response function. The method of this invention can achieve fast coherent accumulation of multiple channels in bistatic MIMO radar and suppress accumulation sidelobes.

Description

Technical Field

[0001] This invention belongs to the field of radar technology, and specifically relates to a multi-channel signal accumulation and sidelobe suppression technology. Background Technology

[0002] With advancements in stealth and aviation technologies, a growing number of high-speed, low-reflection targets, such as near-space vehicles and supersonic missiles, are rapidly emerging. Range migration (RM) caused by high-speed motion and low signal-to-noise ratio (SNR) due to low reflectivity make these targets difficult to detect in radar echoes. Bistatic multiple-input multiple-output (MIMO) radar, as a novel radar mode, transmits orthogonal waveforms for multi-channel signal fusion, thereby improving detection capabilities. Therefore, achieving multi-channel coherent accumulation in bistatic MIMO radar is of great significance.

[0003] To date, regarding the RM (Radon Fourier Transform) problem, single-channel signal accumulation methods based on RFT (Radon Fourier Transform) can effectively suppress the RM effect of targets. The RFT method extracts the target trajectory through Radon transform and designs a phase-compensated filter bank; however, RFT only performs signal accumulation in a single channel. Regarding the inter-channel signal accumulation problem, the multi-channel signal accumulation method based on Ergodic Search (ES) proposed by M. Wang et al. has good accumulation performance, but this method has a high computational cost and does not consider the accumulation sidelobe problem during the search process. The accumulation sidelobe problem in the multi-channel coherent accumulation process of high-speed target MIMO radar has not yet been studied. Accumulation sidelobes specifically refer to the fact that during the accumulation process, some channel peaks are extracted. At this point, the sidelobe energy is not negligible compared to the multi-channel accumulated output peaks, and the accumulation sidelobes will manifest as a series of false targets, affecting subsequent signal processing such as detection and tracking. Therefore, it is urgent to study a multi-channel fast coherent accumulation and accumulation sidelobe suppression method. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for multi-channel coherent accumulation and sidelobe suppression in dual-base MIMO radar, which enables rapid fusion of signals from multiple channels and suppresses accumulated sidelobes generated during the accumulation process.

[0005] The technical solution adopted in this invention is: a method for multi-channel coherent accumulation and sidelobe suppression in dual-base MIMO radar, comprising:

[0006] S1. The radar transmits orthogonal linear frequency modulated signals, and performs pulse compression and channel-in-channel signal accumulation processing on the coupled echoes received by each radar.

[0007] S2. Select a radar reference node, analyze the characteristics of signals in each channel, and determine the search parameters required for the multi-channel accumulation process;

[0008] S3. Design search strategies and phase compensation filters to perform multi-channel fast coherent accumulation;

[0009] S4. Analyze the signal characteristics of the multi-channel accumulated output and design a main lobe retention window to retain the main lobe energy.

[0010] S5. Design the point diffusion response function for accumulated sidelobes to suppress accumulated sidelobes.

[0011] The beneficial effects of this invention are as follows: This invention provides a method for suppressing sidelobes in multi-channel coherent accumulation of bistatic MIMO radar, belonging to the field of radar technology. Addressing the problems of high computational complexity and accumulation sidelobes in multi-channel accumulation methods based on ergonomic search (ES), this invention utilizes Radon-Fourier transform (RFT) to complete signal accumulation within a channel. Furthermore, a fast multi-channel coherent accumulation method is designed based on the geometric topology between the bistatic MIMO radar and the target. Secondly, an accumulation sidelob suppression method is designed. By analyzing the main lobe and sidelobe distribution characteristics of the multi-channel accumulation output, a main lobe energy window function is designed to retain the main lobe energy in the multi-channel accumulation output, and the accumulation sidelobe energy is suppressed based on the point spread response function. The method of this invention can achieve fast coherent accumulation of multi-channel bistatic MIMO radar and suppress accumulation sidelobes. Attached Figure Description

[0012] Figure 1 This is a flowchart of an embodiment of the present invention.

[0013] Figure 2 This is an application scenario in an embodiment of the present invention.

[0014] Figure 3 This is the RFT accumulation result within the radar transmit and receive channel 1 in this embodiment of the invention.

[0015] Figure 4 This is the result accumulated by the ES method in the embodiments of the present invention.

[0016] Figure 5 The results are accumulated for the methods proposed in the embodiments of the present invention;

[0017] in Figure 5 (a) Accumulate results before sidelobe suppression for the proposed method. Figure 5 (b) Results of accumulating sidelobe suppression for the proposed method.

[0018] Figure 6 This is a comparison of the computational complexity of the proposed method and the ES method in the embodiments of the present invention. Detailed Implementation

[0019] This invention primarily utilizes the scientific computing software Matlab R2022a for simulation experiments to verify its correctness. The embodiments of this invention are further described below with reference to the accompanying drawings.

[0020] Please see Figure 1 This invention proposes a geometrically based bistatic MIMO radar multichannel fast coherent accumulation method, which is implemented through the following steps:

[0021] Step 1: The radar transmits an orthogonal linear frequency modulated signal, and performs pulse compression and channel-specific signal accumulation processing on the coupled echo received by each radar.

[0022] In this embodiment, the first The radar transmits the following orthogonal linear frequency modulated signals:

[0023]

[0024] in, Indicates fast time dimension, Indicates the energy of the transmitted signal. Indicates pulse width. Indicates the radar carrier frequency. Indicates the step frequency. Indicates the frequency modulation slope. This refers to the signal bandwidth.

[0025] Then the first The radar in the first The received coupled echo during each pulse is:

[0026]

[0027] in, Indicates the slow time dimension. Represents the speed of light. Indicates the number of coherently accumulated pulses. Indicates the pulse repetition interval. For the distance history of the target in the m-transmitting and n-receiving channels, if the high-speed target is moving horizontally at a constant speed:

[0028]

[0029] in, These represent the equivalent initial radial distance and velocity of the target in the m-transmitting and n-receiving channels, respectively.

[0030] Pulse compression technology can be used to focus the signal energy in the distance dimension and separate four signal channels by utilizing the orthogonality of the transmitted signals. Pulse compression can be achieved by convolving the received echo with the corresponding matched filter, where the matched filter of the m-th transmitting node can be expressed as... The pulse compression results for m-transmitting and n-receiving pulses are then obtained as follows:

[0031]

[0032] Represents the variables in the convolution operation;

[0033] The RFT algorithm is used to accumulate signals within the channel to obtain m transmit and n receive signals. Channel signal accumulation results:

[0034]

[0035] in, These represent the distance dimension and velocity dimension of the RFT algorithm search, respectively. This represents the frequency of the signal transmitted by the m-th node of the radar. At that time, there was a radar operating wavelength. .

[0036] In this embodiment, the system parameter used is: the radial distance of the target from radar 1. and speed The radial distance between the target and radar 2 is 75.00 km and 390.6 m / s. and speed The speeds are 75.18 km and 406.3 m / s, and the radar carrier frequency is... The signal bandwidth is 0.2 GHz. 5MHz, pulse width The pulse repetition interval is 100µs. The number of coherently accumulated pulses is 2ms. 128, step frequency The signal-to-noise ratio of the echo signal received by the radar receiver is -37dB at 5MHz.

[0037] Step 2: Select radar 1 as the reference node and radar 1's transmit and receive channels as the reference channels. Analyze the characteristics of signals from different channels and determine the search parameters required for the multi-channel accumulation process.

[0038] In this embodiment, the signal accumulation results for the m transmit and n receive channels are... When the search distance dimension And search speed dimension At this time, the Doppler phase of each pulse The compensation results in the accumulated peak output within the channel.

[0039] Therefore, the distance between the m-transmit and n-receive channels and the peak position is... Peak position of velocity dimension Peak phase It can be represented as:

[0040]

[0041] and The signals transmitted by the first and second radar nodes are respectively the signal frequencies. At this point, it is found that the output characteristics of each channel are determined by four target parameters: the initial radial distance and velocity of the target from each radar station. Select radar 1 as the reference node. Please refer to [link / reference]. Figure 2 At this point, according to the law of cosines and the velocity decomposition relationship, we can obtain:

[0042]

[0043] in, This is the observation angle of radar station 1. It is the angle between the target and the line of sight of radar stations 1 and 2. This represents the distance between radars 1 and 2. After mathematical simplification, we obtain...

[0044]

[0045] Where the mapping relationship and They are represented as follows:

[0046]

[0047] This refers to the parameters in the mapping relationship, which can be replaced according to the actual parameters in practical applications.

[0048] The output characteristics of each channel can ultimately be represented by three parameters: the initial radial distance of the target from the reference radar node. ,speed and observation angle .

[0049] In this embodiment, the radar spacing Set to 0.75km.

[0050] Step 3: Design of the search strategy and phase compensation filter, and implementation of multi-channel coherent accumulation.

[0051] In this embodiment, step 3 includes the following processes: setting the search parameter range and search parameter step, calculating the extraction coordinates of each channel and extracting the signal, designing the phase compensation filter, and coherently accumulating the multi-channel signal.

[0052] First, we need to set the search parameter range and the search parameter step. This represents the discrete search sequence of the target's initial radial distance, velocity, and observation angle from the reference radar node, where...

[0053]

[0054] in, These represent the maximum and minimum values ​​of the equivalent initial radial range and velocity, respectively. The range search step can be determined based on radar parameters and system resolution. Speed ​​search step Angle search step The required accuracy is determined by the system. Additionally, the distance from the search point... Speed ​​search points , number of angle search points .

[0055] Secondly, the calculation of extraction coordinates and signal extraction for each channel is required. For an m-transmit / n-receive channel, the extraction coordinates along the distance and velocity dimensions are determined by the following formula:

[0056]

[0057] in The initial radial distance and velocity discrete search sequence of the target from another radar node are determined by the following formula:

[0058]

[0059] Then the signal extracted by the m-transmitting and n-receiving channels is:

[0060] ;

[0061] Next is the design of the phase compensation filter. Based on the peak phase relationship between channels analyzed in step 2, the phase compensation filter can be constructed as follows:

[0062]

[0063] Finally, there is the multi-channel signal coherent accumulation. The multi-channel signal accumulation result is obtained by multiplying the extracted signals with the phase compensation filter and then superimposing them. as follows:

[0064] ;

[0065] In this embodiment, the distance search range is 7.45km to 7.55km, the speed search range is 375m / s to 440m / s, and the angle search step is set to 0.5. Angle search range .

[0066] Step 4: Accumulate and retain the main lobe energy, analyze the signal characteristics of the multi-channel accumulated output, and design the main lobe energy retention window function. This preserves the energy of the main lobe.

[0067] In this embodiment, if the three parameters of the search are... With the target true parameters If they are equal, then each channel extracts coordinates. with peak coordinates When the signals are equal, the peak values ​​of the four channels are extracted and coherently accumulated. The accumulation result can be simplified as follows:

[0068]

[0069] Peak accumulation output However, if the peak values ​​of some channels are extracted and accumulated, a non-negligible output will be generated, known as accumulated sidelobes. In a dual-base MIMO radar architecture, if the peak value of one channel is extracted during the multi-channel accumulation process... Then the peak-to-cumulative sidelobe ratio of the output at this time is This output will affect subsequent signal processing procedures such as target detection and tracking. Therefore, it is necessary to suppress accumulated sidelobes.

[0070] First, based on the cumulative output characteristics of the target, accumulate the output. The energy of the main lobe is concentrated in a three-dimensional window. Inside:

[0071]

[0072] The window lengths in its distance, velocity, and angle dimensions Determined by the first zero of the sinc function:

[0073]

[0074] The window length in the angular dimension should satisfy the following formula:

[0075]

[0076] The main lobe preservation result can then be obtained based on this window function. .

[0077] Step 5: Suppress the accumulated sidelobe energy. Design the point diffusion response function for the accumulated sidelobe to suppress the accumulated sidelobe.

[0078] In this embodiment, to construct the point spread response function for accumulating sidelobes, it is first necessary to estimate each target parameter:

[0079]

[0080] in These are the initial radial distance and velocity estimates of the target from each radar station. Let be the energy estimates for each channel. Then, the point spread response function of the multi-channel accumulated output is... Reconstruct as follows:

[0081]

[0082] in Let n and m represent the estimated radial distance and velocity of the target from radar station n and radar station m, respectively. Then, based on the point spread response function, the sidelobe point spread response function can be obtained. .

[0083] In this embodiment, the main lobe energy retained in the multi-channel accumulated output is... With the constructed sidelobe point diffusion response Subtraction yields the result of accumulated sidelobe suppression. :

[0084] ;

[0085] To demonstrate the effectiveness of this method, Figure 3 The results of the accumulation within a single transmit and receive channel obtained using the RFT method are shown. Figure 4 The results of the traditional ES method show that there are a large number of accumulated sidelobes, which appear as a series of false targets. Figure 5 (a) This is the result of the present invention without accumulated sidelobe suppression, resulting in a series of false targets. After accumulated sidelobe suppression by the present invention, such as Figure 5 (b) shows that the accumulated sidelobes are successfully eliminated at this point, which is beneficial for subsequent target tracking and detection. Furthermore, Figure 5 The multi-channel accumulation peak value is Figure 3 The fact that the single-channel accumulation peak value is four times that of the present invention indicates that the present invention can successfully achieve multi-channel coherent accumulation in dual-base MIMO radar. Figure 6 A comparison of the computational complexity required by the method of this invention with that of the traditional ES method shows that the method of this invention not only suppresses the accumulation of sidelobes but also significantly reduces computational complexity.

[0086] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of the claims of the invention.

Claims

1. A method for multi-channel coherent accumulation and sidelobe suppression in bistatic MIMO radar, characterized in that, include: S1. The radar transmits orthogonal linear frequency modulated signals, and performs pulse compression and channel-in-channel signal accumulation processing on the coupled echoes received by each radar. S2. Select a radar reference node, analyze the characteristics of signals in each channel, and determine the search parameters required for the multi-channel accumulation process; S3. Design a search strategy and phase compensation filter to perform multi-channel fast coherent accumulation; the search strategy in step S3 specifically includes: First, determine the search parameter range and the search parameter step; Let the maximum and minimum values ​​of the search equivalent initial radial distance and motion velocity be respectively... The range search step is determined based on radar parameters and system resolution. Speed ​​search step Angle search step Determined by the required accuracy of the system. Represents the speed of light. For signal bandwidth, Indicates the number of coherently accumulated pulses. Indicates the pulse repetition interval; distance from the search point. Speed ​​search points , number of angle search points The discrete search sequence of the target's initial radial distance, velocity, and observation angle from the reference radar node is then expressed as: ； in, , , These represent the discrete search sequences of the target's initial radial distance, velocity, and observation angle from the reference radar node, respectively. Secondly, the extraction coordinates and signal extraction for each channel are calculated; for an m-transmit and n-receive channel, the extraction coordinates along the distance and velocity dimensions are determined by the following formula: ； in, , The initial radial distance and velocity discrete search sequence of the target from another radar node are determined by the following formula: ； and The mapping relationship is represented by the expression: ； Indicates the distance between radars 1 and 2; Then the signal extracted by the m-transmitting and n-receiving channels is: ； in, Indicates the energy of the transmitted signal. Indicates the slow time dimension. This represents the frequency of the signal transmitted by the m-th node of the radar. Indicates the radar operating wavelength. Let represent the equivalent initial radial distance and velocity of the target in the m-transmitting and n-receiving channels, respectively. S4. Analyze the signal characteristics of the multi-channel accumulated output and design a main lobe retention window to retain the main lobe energy; the main lobe retention window in step S4 is represented as follows: ； These represent the window lengths for the distance, velocity, and angle dimensions, respectively. This indicates the radial distance of the target from the reference radar. This represents the radial velocity of the target relative to the reference radar. Indicates the observation angle of the reference radar; S5. Design the point diffusion response function for accumulated sidelobes to suppress accumulated sidelobes.

2. The method for multi-channel coherent accumulation and sidelobe suppression in a dual-base MIMO radar according to claim 1, characterized in that, In step S1, the RFT algorithm is used to accumulate signals within the channel.

3. The method for multi-channel coherent accumulation and sidelobe suppression in a dual-base MIMO radar according to claim 1, characterized in that, The search parameters in step S2 include: the initial radial distance, velocity, and observation angle of the target from the reference radar node, and a discrete search sequence.

4. The method for multi-channel coherent accumulation and sidelobe suppression in a dual-base MIMO radar according to claim 1, characterized in that, The phase compensation filter in step S3 is expressed as follows: 。 5. The method for multi-channel coherent accumulation and sidelobe suppression in a dual-base MIMO radar according to claim 4, characterized in that, Determined by the first zero of the sinc function: ； The following formula should be satisfied: ； in, This indicates the radial distance of the target from radar 2. This indicates the radial velocity of the target from radar 2.

6. The method for multi-channel coherent accumulation and sidelobe suppression in a bistatic MIMO radar according to claim 5, characterized in that, In step S5, the sidelobe point diffusion response function is accumulated, and its expression is: ； in, These are the estimated energy values ​​for each channel. This represents the estimated radial distance between the target and radar station n. This represents the estimated radial velocity of the target at a distance n from the radar station. This represents the estimated radial distance (m) between the target and the radar station. This represents the estimated radial velocity of the target at a distance of m from the radar station.

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