Radar waveform design method for suppressing autocorrelation sidelobe based on multi-carrier phase coding

Abstract

The invention relates to a radar waveform design method for suppressing an autocorrelation sidelobe based on multi-carrier phase coding. The method comprises the following steps: acquiring a chaos sequence with pseudo-randomness; according to the chaos sequence, an OFDM method and a phase encoding method are adopted for processing, and an MCPC radar signal is obtained; according to the MCPC radar signal, the power difference between a maximized target and a sidelobe peak value, the minimum peak value sidelobe level and the minimum integral sidelobe level are accurately measured for processing, and a pulse compression sidelobe of the radar signal is obtained; pulse compression sidelobes of the radar signals are processed in a subcarrier amplitude windowing mode, and radar signals of multi-carrier phase coding suppression self-correlation and cross-correlation sidelobes are obtained; the self-correlation sidelobe is taken as an optimization target, and a genetic algorithm is adopted to optimize a carrier weighted window function to reduce the self-correlation sidelobe. The radar signal designed by the method has good anti-interference performance and sidelobe reduction performance.

Description

Technical Field

[0001] The present application relates to the technical field of radar waveform design, and in particular to a radar waveform design method based on multi-carrier phase coding to suppress autocorrelation side lobes. Background Art

[0002] Early radar systems were used to make some simple measurements, including time delay and distance. Using continuous wave radar, speed can also be measured. As radar systems become more complex and accurate, it is inevitable to consider the issues of accuracy and resolution. As an electronic device for space detection, radar uses the electromagnetic wave echoes passing through space targets to locate them, and at the same time obtains spatial parameter information, such as relative distance, radial velocity, angle, etc. MIMO (Multiple Input Multiple Output) radar is a new type of radar proposed in this context with application needs as the driving force. MIMO radar has been proven to have higher resolution and anti-interference potential. MIMO radar has more degrees of freedom, which enables it to detect speed in target detection, interference / clutter suppression, transmission pattern design, and radar waveform optimization design. Therefore, it has been widely used in radar, communication, navigation and other fields.

[0003] Pulse compression technology plays an extremely important role in radar signal processing. It solves the contradiction between radar range and range resolution. Digital pulse compression has been proven to be more effective than analog pulse compression and can be implemented with binary sequences, polyphase sequences, and frequency coded sequences. However, after the pulse compression processing of the radar waveform, range sidelobes will be generated. Excessive sidelobes will seriously affect the detection of weak target signals and cause signal loss. Summary of the invention

[0004] Based on this, it is necessary to provide a radar waveform design method based on multi-carrier phase coding to suppress autocorrelation sidelobes in response to the above technical problems.

[0005] A radar waveform design method for suppressing autocorrelation sidelobes based on multi-carrier phase coding, the method comprising: Get a chaotic sequence with pseudo-randomness.

[0006] According to the chaotic sequence, OFDM method and phase coding method are used to process and obtain the MCPC radar signal.

[0007] According to the MCPC radar signal, the pulse compression sidelobe of the radar signal is obtained by processing it according to the criteria of maximizing the power difference between the target and the sidelobe peak, minimizing the peak sidelobe level and minimizing the integrated sidelobe level.

[0008] The pulse compression sidelobe of the radar signal is processed by using a subcarrier amplitude windowing method to obtain a radar signal with multi-carrier phase coding that suppresses autocorrelation and cross-correlation sidelobes; the window function used in the subcarrier amplitude windowing method is a carrier weighted window function optimized by a genetic algorithm in the frequency domain.

[0009] In one embodiment, obtaining a chaotic sequence with pseudo-randomness includes: using an iterative formula of Logistic mapping to generate a sequence, and then quantizing and encoding the sequence to obtain a chaotic sequence with pseudo-randomness, and the quantization rule is: ; in, is the chaotic phase coding value of the nth subcarrier, is the quantization order, The first values, is the ceiling function.

[0010] In one embodiment, the complex envelope of the radar signal after windowing with multi-carrier phase coding to suppress autocorrelation and cross-correlation side lobes is: ; ; in, The complex envelope of the radar signal after windowing for multi-carrier phase coding to suppress autocorrelation and cross-correlation sidelobes. , It is The frequency weighted amplitude on the subcarriers, is the weighted phase, is the complex envelope of the subcarrier signal, For the p subcarrier frequencies, is the duration of a single chip, For the p Subcarrier m Phase coding on symbols, P is the number of carriers, M is the number of code elements, is the time variable, j Is an imaginary unit.

[0011] In one of the embodiments, the window function used in the subcarrier amplitude windowing method is a Hamming window optimized by a genetic algorithm in the frequency domain.

[0012] In one of the embodiments, the window function used in the subcarrier amplitude windowing method is a Hening window optimized by a genetic algorithm in the frequency domain.

[0013] In one of the embodiments, the window function used in the subcarrier amplitude windowing method is a Blackman window optimized by genetic algorithm in the frequency domain.

[0014] In one of the embodiments, the window function used in the subcarrier amplitude windowing method is a Caesar window optimized by a genetic algorithm in the frequency domain.

[0015] In one embodiment, the pulse compression sidelobe of the radar signal is obtained by processing the MCPC radar signal using the criteria of maximizing the power difference between the target and the sidelobe peak, minimizing the peak sidelobe level, and minimizing the integrated sidelobe level, including: After the MCPC radar signal is transmitted, the echo signal is received and the envelope peak-to-average power ratio, peak sidelobe ratio and integrated sidelobe level ratio of the echo signal are calculated.

[0016] Aiming at maximizing the envelope peak-to-average power ratio, minimizing the peak-to-sidelobe ratio and minimizing the integrated sidelobe level ratio of the echo signal, the parameters of the MCPC radar signal are adjusted to obtain the pulse compression sidelobe of the radar signal.

[0017] In one embodiment, the method further comprises: The anti-interference performance of radar signals with multi-carrier phase coding suppressing autocorrelation and cross-correlation sidelobes is evaluated.

[0018] In one embodiment, anti-interference performance evaluation is performed on a radar signal with multi-carrier phase coding to suppress autocorrelation and cross-correlation side lobes, including: Acquire the radar signal with multi-carrier phase coding to suppress the autocorrelation and cross-correlation side lobes, and perform STFT transformation on the acquired radar signal to obtain: ; in, is the total echo signal, The radar receiving signal is a radar signal with multi-carrier phase coding that suppresses the autocorrelation and cross-correlation side lobes. is the frequency sliding window function, is the frequency variable, representing the frequency value in the frequency domain after Fourier transform, is the integration variable, is the time variable.

[0019] A matched filter function is constructed based on the total echo signal; the matched filter function is: ; in, is the matched filter function.

[0020] Based on the total echo signal and the matched filter function, the pulse pressure output after intermittent sampling and forwarding interference suppression is obtained.

[0021] Based on the total echo signal and the pulse pressure output after intermittent sampling and forwarding interference suppression, the signal-to-interference ratio improvement factor is obtained: ; in, is the signal-to-interference ratio improvement factor, is the ratio of signal to interference capability, is the ratio of the peak value of the signal after matched filtering to the interference peak value.

[0022] The above-mentioned radar waveform design method based on multi-carrier phase coding to suppress autocorrelation sidelobes includes: obtaining a chaotic sequence with pseudo-randomness; processing the chaotic sequence using OFDM method and phase coding method to obtain MCPC radar signal; processing the MCPC radar signal using the maximization of the power difference between the target and the sidelobe peak, the minimum peak sidelobe level, and the minimum integrated sidelobe level to obtain the pulse compression sidelobe of the radar signal; processing the pulse compression sidelobe of the radar signal using the subcarrier amplitude windowing method to obtain a radar signal with multi-carrier phase coding to suppress autocorrelation and cross-correlation sidelobes; taking the autocorrelation sidelobe as the optimization target, a genetic algorithm is used to optimize the carrier weighted window function to reduce the autocorrelation sidelobe. The radar signal designed using this method has good anti-interference performance and sidelobe reduction performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic flow chart of a radar waveform design method for suppressing autocorrelation side lobes based on multi-carrier phase coding in one embodiment; Figure 2 is a schematic diagram of the time-frequency structure of an ACC-MCPC signal in another embodiment; Figure 3 : is a time domain diagram and a frequency domain diagram of a pulse in another embodiment, wherein Figure 3 (a) is the time domain diagram of the pulse. Figure 3 (b) is the frequency domain diagram of the pulse; Figure 4 Schematic diagram of the autocorrelation main-sidelobe ratio in another embodiment, wherein Figure 4 (a) is a schematic diagram of the main-sidelobe ratio of autocorrelation without windowing. Figure 4 (b) is a schematic diagram of the cross-correlation main-sidelobe ratio. Figure 4 (c) is a schematic diagram of adding a Hamming window. Figure 4 (d) is a schematic diagram of adding a Hanning window. Figure 4 (e) is a schematic diagram of adding a Blackman window. Figure 4 (f) is a schematic diagram of adding a Kaiser (Nn, 10) window. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technology. The main idea of ​​OFDM is to decompose a high-speed data stream into multiple parallel low-speed sub-data streams and transmit them on multiple orthogonal sub-carriers.

[0026] Multi-carrier Phased Coded (MCPC) radar waveform is a new type of broadband radar waveform. It is a combination of phase-coded signal and orthogonal frequency division multiplexing technology. Its core idea is to disperse the information to be transmitted onto multiple carriers and perform phase encoding on each carrier to improve the signal's anti-interference ability, transmission efficiency and resolution.

[0027] Logistic mapping is a simple mathematical mapping that is often used to describe ecological phenomena such as population growth. It is also a classic example in chaos theory. Logistic mapping is an iterative process with the following form: ,in, is the signal at time k, is the signal at time k+1. Using the iterative formula of Logistic mapping, a unique chaotic sequence can be generated. By quantizing and encoding the sequence, it can be used to encode the phase of the signal.

[0028] Short-Time Fourier Transform (STFT) is a time-frequency analysis method used in signal processing. It slides a short-time window on the signal and performs Fourier transform on the signal in each window to obtain the change of the local frequency information of the signal over time.

[0029] In one embodiment, Figure 1 As shown, a radar waveform design method for suppressing autocorrelation sidelobes based on multi-carrier phase coding is provided, and the method comprises the following steps: Step 100: Obtain a chaotic sequence with pseudo-randomness.

[0030] Specifically, due to the inherent non-periodicity and high unpredictability of chaotic sequences, they provide significant advantages for multi-carrier phase coding (MCPC) signals. Due to their non-periodicity and unpredictability, chaotic sequences can effectively reduce the cross-correlation of signals, thereby reducing interference and enhancing the radar's target resolution capability. At the same time, the complexity of chaotic sequences improves the concealment of radar signals and enhances the system's electronic countermeasures.

[0031] Step 102: Process the chaotic sequence using an OFDM method and a phase coding method to obtain an MCPC radar signal.

[0032] Specifically, pulse compression technology plays an extremely important role in radar signal processing, which solves the contradiction between radar range and range resolution. Digital pulse compression has been proven to be more effective than analog pulse compression, and can be implemented with binary sequences, polyphase sequences, and frequency coded sequences. However, after the pulse compression processing of the radar waveform, range sidelobes will be generated. Too many sidelobes will seriously affect the detection of weak target signals and cause signal loss. Orthogonal frequency division multiplexing (OFDM) technology can be used, which can be used for radar detection to modulate a single carrier transmission signal onto multiple carriers. The signal processed by OFDM technology has orthogonal overlap between subcarriers, and it can be transmitted after carrier superposition, so it has a higher frequency band utilization. OFDM technology is combined with phase coding technology to form a multi-carrier phase coded (MCPC) signal, which has a large time-bandwidth product, which can improve the range resolution.

[0033] The multi-carrier phase coded (MCPC) radar waveform is a new type of wideband radar waveform that is a combination of phase coded signal and orthogonal frequency division multiplexing technology.

[0034] Step 104: Process the MCPC radar signal using the criteria of maximizing the power difference between the target and the sidelobe peak, minimizing the peak sidelobe level, and minimizing the integrated sidelobe level to obtain the pulse compression sidelobe of the radar signal.

[0035] Step 106: The pulse compression side lobes of the radar signal are processed by using a subcarrier amplitude windowing method to obtain a radar signal with multi-carrier phase coding to suppress autocorrelation and cross-correlation side lobes; the window function used in the subcarrier amplitude windowing method is a carrier weighted window function optimized by a genetic algorithm in the frequency domain.

[0036] Specifically, the radar signal with multi-carrier phase coding to suppress autocorrelation and cross-correlation sidelobes is referred to as ACC--MCPC signal. The time-frequency structure of ACC-MCPC signal is as follows: Figure 2 shown.

[0037] The pulse compression sidelobe of the ACC-MCPC signal is improved, and because it is derived from the MCPC radar signal, it also inherits other advantages of the MCPC radar signal. Compared with the LFM signal, the main lobe of the LFM signal will be widened, while the main lobe of the MCPC radar signal is not widened, and the anti-interference ability is better than the LFM signal. Compared with the literature (Li, J., Liu. M., Ou, JP, Wang W., “A Novel Radar Waveform Design for Suppressing AutocorrelationSide-Lobe Based on Chaotic and Single Fusion Encoding Method,” Progress InElectromagnetics Research M, Vol. 111, 77-88, 2022.), under the same parameters, the sidelobe can be reduced to a lower level. In order to obtain a low peak-to-sidelobe ratio (PSLR), sidelobe control is particularly important.

[0038] The ACC-MCPC signal has the following characteristics: (1) The ACC-MCPC signal consists of P subcarriers, each of which contains M bits of phase encoding, and each phase encoding chip has the same width.

[0039] (2) To ensure orthogonality between subcarriers, the frequency spacing between adjacent subcarriers is the inverse of the chip width.

[0040] (3) Different modulation modes can be used in the time domain, and the amplitude and phase of the subcarrier can be weighted in the frequency domain.

[0041] Genetic Algorithm (GA) is a search heuristic algorithm that simulates the principles of natural selection and genetics and is used to solve optimization and search problems. In this method, a genetic algorithm is used in the frequency domain to optimize the carrier weighted window function, and the optimization goal is to minimize the sidelobe level. The window function parameters can be encoded into a chromosome form that can be processed by the genetic algorithm, and a certain number of individuals are randomly generated as the initial population, each of which represents a set of possible window function coefficients. A fitness function is defined to evaluate the performance of each individual, and the fitness function should reflect the optimization goal. A new population is generated through genetic operations. In each iteration of the genetic algorithm, the individual's genes need to be decoded into window function coefficients, and then the performance of the window function is analyzed in the frequency domain, and the optimal value is selected using the genetic algorithm.

[0042] Taking the Hamming window as an example, the process of optimizing the carrier weighted window function using the genetic algorithm in the frequency domain is explained, which specifically includes: The Hamming window is a weighted rectangular window, and its form is as follows: (1) in, is the window function n values, N is the length of the window function.

[0043] Although the standard Hamming window has only two parameters (0.54 and 0.46), for optimization, more parameters can be considered, such as the sidelobe decay rate or the shape of the window function; (2) in, , , There are three optimization parameters.

[0044] First, determine the interval of the number: , , .

[0045] Then, initialize the population, each individual , , Specifically, a certain number of individuals are randomly generated as the initial population, and each individual , , The parameters are within the appropriate range; Iterate the optimization until the optimal Hamming window parameters are found.

[0046] Finally, the optimal parameters are output, such as , , .

[0047] In the above-mentioned radar waveform design method based on multi-carrier phase coding to suppress autocorrelation sidelobes, the method includes: obtaining a chaotic sequence with pseudo-randomness; processing the chaotic sequence using OFDM method and phase coding method to obtain MCPC radar signal; processing the MCPC radar signal using the maximization of the power difference between the target and the sidelobe peak, the minimum peak sidelobe level, and the minimum integrated sidelobe level to obtain the pulse compression sidelobe of the radar signal; processing the pulse compression sidelobe of the radar signal using the subcarrier amplitude windowing method to obtain a radar signal with multi-carrier phase coding to suppress autocorrelation and cross-correlation sidelobes; taking the autocorrelation sidelobes as the optimization target, a genetic algorithm is used to optimize the carrier weighted window function to reduce the autocorrelation sidelobes. The radar signal designed using this method has good anti-interference performance and sidelobe reduction performance.

[0048] In one embodiment, step 100 includes: using the iterative formula of Logistic mapping to generate a sequence, and then quantizing and encoding the sequence to obtain a chaotic sequence with pseudo-randomness, and the quantization rule is: (3) in, is the chaotic phase coding value of the nth subcarrier, is the quantization order, which determines the resolution of the chaotic sequence. Here, it is 2, which is a chaotic two-phase code. The first in the chaotic sequence values, is a ceiling function, for example, ceil(2.3) = 3.

[0049] Specifically, in multi-carrier phase coding, chaotic sequences are widely used to generate chaotic two-phase codes. The iterative expression of the Logistic map is shown in Table 1.

[0050] Table 1 Logistic mapping chaotic sequence iteration expression

[0051] Using the iterative formula of Logistic mapping, a unique chaotic sequence can be generated. By quantizing and encoding the sequence, it can be used to encode the phase of the signal. The specific quantization rule is shown in formula (3).

[0052] The autocorrelation function of the Logistic map has the lowest peak-to-sidelobe ratio, and its main peak is most prominent relative to the height of the sidelobe, showing the best autocorrelation properties. This characteristic makes the sequence generated by the Logistic map perform best in signal recognition and interference suppression, so the Logistic map is used in this application to phase encode the signal.

[0053] In one embodiment, the ACC-MCPC signal has good low interception and anti-interference performance, and the complex envelope of the radar signal with multi-carrier phase coding suppressing autocorrelation and cross-correlation side lobes after windowing is: (4) (5) in, The complex envelope of the radar signal after windowing for multi-carrier phase coding to suppress autocorrelation and cross-correlation sidelobes. , It is The frequency weighted amplitude on the subcarriers, is the weighted phase, is the complex envelope of the subcarrier signal, For the psubcarrier frequencies, is the duration of a single chip, For the p Subcarrier m Phase coding on symbols, P is the number of carriers, M is the number of code elements, is the time variable, j Is an imaginary unit.

[0054] Specifically, located at a distance The echo signal at the scattering point target is: (6) in is the echo amplitude, For delay, The speed of light.

[0055] In one embodiment, the window function used in the subcarrier amplitude windowing method in step 106 is a Hamming window optimized by genetic algorithm in the frequency domain.

[0056] In one embodiment, the window function used in the subcarrier amplitude windowing method in step 106 is a Hening window optimized by genetic algorithm in the frequency domain.

[0057] In one embodiment, the window function used in the subcarrier amplitude windowing method in step 106 is a Blackman window optimized by genetic algorithm in the frequency domain.

[0058] In one embodiment, the window function used in the subcarrier amplitude windowing method in step 106 is a Caesar window optimized by genetic algorithm in the frequency domain.

[0059] In one embodiment, step 104 includes: after transmitting the MCPC radar signal, receiving the echo signal, calculating the envelope peak-to-average power ratio, the peak sidelobe ratio and the integrated sidelobe level ratio of the echo signal; adjusting the parameters of the MCPC radar signal with the goal of maximizing the envelope peak-to-average power ratio, minimizing the peak sidelobe ratio and minimizing the integrated sidelobe level ratio of the echo signal to obtain the pulse compression sidelobe of the radar signal.

[0060] Specifically, if the cross-correlation peak or autocorrelation sidelobe is too high, a false target will be generated or the real weak target nearby will be covered. Therefore, the purpose of introducing OFDM orthogonal signal design is to make the cross-correlation as small as possible and the autocorrelation sidelobe as low as possible. In this paper, a waveform optimization design method for minimizing the sidelobe of autocorrelation and cross-correlation is designed.

[0061] In order to analyze the matched filtering results of the ACC-MCPC signal, the fuzzy function is calculated as follows: The ambiguity function of the MCPC radar signal is: (7) It is expressed as: (8) in, is the impulse response coefficient of the matched filter, for The fuzzy function.

[0062] In the research field of MCPC systems, the peak-to-average power ratio (PAPR) of MCPC radar signals has always been an important research hotspot. It will affect the power and ranging range of the transmitter, making the radar system unable to achieve high operating efficiency. PAPR is the ratio of the peak value to the average value of the synthesized transmitted signal. When transmitting information, the amplitude and phase of each subcarrier can be assumed to be independent random events. When the amplitude and phase of all subcarriers are consistent (the symbols of all subcarriers are the same), the superimposed synthetic wave will have a very large peak value, which can exceed the average value by many dB. In general, the more subcarriers there are, the greater the PAPR.

[0063] High peak-to-average power ratio is the main problem of using MCPC radar signals, which is the main reason for bit error rate reduction and spectrum expansion in nonlinear channels. Therefore, the peak-to-average power ratio problem of MCPC radar signals needs to be improved, and how to obtain a low peak-to-average power ratio is still a problem in the current radar field.

[0064] The peak-to-average ratio, as the name implies, is the ratio of the peak power of the signal envelope to the average power: (9) In the above formula, is the echo signal, is the total time of linear amplification of the signal in the transmitter. PAPR is a parameter that measures the fluctuation characteristics of the signal envelope and is one of the important indicators for evaluating signal performance.

[0065] is the complex envelope of the signal. The amplitude of the complex envelope of the MCPC pulse of a symbol can be expressed as follows: (10) It is a value that measures the envelope fluctuation of the air interface signal and is one of the important indicators for measuring the performance of MCPC radar signals.

[0066] Peak sidelobe level and integrated sidelobe level are important indicators for measuring sidelobe. In order to ensure that the synthesized beam pattern has the desired main lobe shape and low sidelobe characteristics, this paper proposes a low sidelobe transmission beam pattern optimization design method by maximizing the power difference between the target and the sidelobe peak, the minimum peak sidelobe level, the minimum integrated sidelobe level and other criteria, so that the energy radiated in the sidelobe is as small as possible, thereby improving the radar's anti-interception performance. The peak sidelobe level (PSL) calculation can realize the calculation of the peak sidelobe level of the radar signal and further analyze the sidelobe characteristics of the signal.

[0067] To measure the autocorrelation characteristics of chaotic sequences, the paper uses the Peak-to-Side Lobe Ratio (PSLR) as an indicator, which is the ratio of the peak power of the autocorrelation function to the maximum power of the sidelobe. The lower the PSLR value, the better the autocorrelation performance.

[0068] Peak-to-side lobe ratio (PSLR): The ratio of the maximum side lobe to the main lobe height, expressed in decibels (dB). The PSLR expression is: (11) Another metric used to evaluate autocorrelation performance is the Integrated Sidelobe Level Ratio (ISLR). The ratio of the sidelobe energy to the mainlobe energy. It is defined as the ratio of the total power in the compressed sidelobes of the autocorrelation pulse to the peak power.

[0069] Integrated sidelobe level ratio: (12) in, is the total power, is the main lobe power.

[0070] In one of the embodiments, the method further includes: evaluating the anti-interference performance of radar signals with multi-carrier phase coding suppressing autocorrelation and cross-correlation side lobes.

[0071] In one embodiment, the anti-interference performance of the radar signal with multi-carrier phase coding suppressing autocorrelation and cross-correlation side lobes is evaluated, including: obtaining the radar signal with multi-carrier phase coding suppressing autocorrelation and cross-correlation side lobes, and performing STFT transformation on the obtained radar signal to obtain a total echo signal as follows: (13) in, is the total echo signal, The radar receiving signal is a radar signal with multi-carrier phase coding that suppresses the autocorrelation and cross-correlation side lobes. is the frequency sliding window function, is the frequency variable, is the integral variable, used to represent the signal in the integral operation The values ​​at different time points, is a time variable, representing the position of the window function on the time axis.

[0072] A matched filter function is constructed based on the total echo signal; the matched filter function is: (14) in, is the matched filter function.

[0073] Based on the total echo signal and the matched filter function, the pulse pressure output after intermittent sampling and forwarding interference suppression is obtained; based on the total echo signal and the pulse pressure output after intermittent sampling and forwarding interference suppression, the signal-to-interference ratio improvement factor is obtained as follows: (15) in, is the signal-to-interference ratio improvement factor, is the ratio of signal to interference capability, is the ratio of the peak value of the signal after matched filtering to the interference peak value.

[0074] Specifically, the signal-to-interference ratio improvement factor is a comprehensive measure of the performance of the intermittent sampling forwarding interference suppression method proposed in the present application.

[0075] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0076] In a verification example, simulation parameters of the simulation experiment are shown in Table 2.

[0077] Table 2 Simulation parameters of simulation experiment

[0078] The time domain and frequency domain diagrams of the pulse are as follows Figure 3 As shown, Figure 3 (a) is the time domain diagram of the pulse. Figure 3(b) is the frequency domain diagram of the pulse. The simplest way to suppress the autocorrelation sidelobe level of the radar waveform is to solve it by adding a window. In order to reduce the autocorrelation sidelobe, a windowing process can be performed. Different windows have different effects. This embodiment uses the Hamming window, Hanning window, Blackman window and Kaiser window. The schematic diagram of the autocorrelation main-sidelobe ratio is shown in Figure 4 As shown, Figure 4 (a) is a schematic diagram of the main-sidelobe ratio of autocorrelation without windowing. Figure 4 (b) is a schematic diagram of the cross-correlation main-sidelobe ratio. Figure 4 (c) is a schematic diagram of adding a Hamming window. Figure 4 (d) is a schematic diagram of adding a Hanning window. Figure 4 The middle (e) is a schematic diagram of adding a Blackman window. Figure 4 (f) in the middle is a schematic diagram of adding a Kaiser (Nn, 10) window. By changing the length n and Parameters affect the value of the side lobe of the window function. The parameters of the window function are changed and the mathematical formula is improved to obtain a lower peak side lobe level. The effectiveness of this method is proved by comparing with the existing technology.

[0079] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A radar waveform design method based on multi-carrier phase coding to suppress autocorrelation sidelobes, characterized in that: The method comprises: Obtain a chaotic sequence with pseudo-randomness; According to the chaotic sequence, an OFDM method and a phase coding method are used to process to obtain an MCPC radar signal; According to the MCPC radar signal, the pulse compression sidelobe of the radar signal is obtained by processing the radar signal using the criteria of maximizing the power difference between the target and the sidelobe peak, minimizing the peak sidelobe level, and minimizing the integrated sidelobe level; The pulse compression side lobes of the radar signal are processed by using a subcarrier amplitude windowing method to obtain a radar signal with multi-carrier phase coding to suppress autocorrelation and cross-correlation side lobes; the window function used in the subcarrier amplitude windowing method is a carrier weighted window function optimized by a genetic algorithm in the frequency domain.

2. The radar waveform design method based on multi-carrier phase coding to suppress autocorrelation side lobes according to claim 1 is characterized in that: Obtain chaotic sequences with pseudo-randomness, including: The iterative formula of Logistic mapping is used to generate a sequence, and then the sequence is quantized and encoded to obtain a chaotic sequence with pseudo-randomness. The quantization rule is: in, For the n The chaotic phase coding value of the subcarrier, is the quantization order, The first values, is the ceiling function.

3. The radar waveform design method based on multi-carrier phase coding to suppress autocorrelation side lobes according to claim 1 is characterized in that: The complex envelope of the radar signal after windowing with multi-carrier phase coding to suppress autocorrelation and cross-correlation side lobes is: in, The complex envelope of the radar signal after windowing for multi-carrier phase coding to suppress autocorrelation and cross-correlation sidelobes. , It is The frequency weighted amplitude on the subcarriers, is the weighted phase, is the complex envelope of the subcarrier signal, For the p subcarrier frequencies, is the duration of a single chip, For the p Subcarrier m Phase coding on symbols, P is the number of carriers, M is the number of code elements, is the time variable, j Is an imaginary unit.

4. The radar waveform design method based on multi-carrier phase coding to suppress autocorrelation side lobes according to claim 1 is characterized in that: The window function used in the subcarrier amplitude windowing method is a Hamming window optimized by a genetic algorithm in the frequency domain.

5. The radar waveform design method based on multi-carrier phase coding to suppress autocorrelation side lobes according to claim 1 is characterized in that: The window function used in the subcarrier amplitude windowing method is a Hening window optimized by a genetic algorithm in the frequency domain.

6. The radar waveform design method based on multi-carrier phase coding to suppress autocorrelation side lobes according to claim 1 is characterized in that: The window function used in the subcarrier amplitude windowing method is a Blackman window optimized by genetic algorithm in the frequency domain.

7. The radar waveform design method based on multi-carrier phase coding to suppress autocorrelation side lobes according to claim 1 is characterized in that: The window function used in the subcarrier amplitude windowing method is a Caesar window optimized by a genetic algorithm in the frequency domain.

8. The radar waveform design method based on multi-carrier phase coding to suppress autocorrelation side lobes according to claim 1 is characterized in that: According to the MCPC radar signal, the pulse compression sidelobe of the radar signal is obtained by processing the radar signal according to the criteria of maximizing the power difference between the target and the sidelobe peak, the minimum peak sidelobe level, and the minimum integrated sidelobe level, including: After transmitting the MCPC radar signal, receiving the echo signal, and calculating the envelope peak-to-average power ratio, peak sidelobe ratio and integrated sidelobe level ratio of the echo signal; With the goal of maximizing the envelope peak-to-average power ratio of the echo signal, minimizing the peak sidelobe ratio and minimizing the integrated sidelobe level ratio, the parameters of the MCPC radar signal are adjusted to obtain the pulse compression sidelobe of the radar signal.

9. The radar waveform design method based on multi-carrier phase coding to suppress autocorrelation side lobes according to claim 1 is characterized in that: The method further comprises: The anti-interference performance of radar signals with multi-carrier phase coding suppressing autocorrelation and cross-correlation sidelobes is evaluated.

10. The radar waveform design method based on multi-carrier phase coding to suppress autocorrelation side lobes according to claim 9 is characterized in that: The anti-interference performance of radar signals with multi-carrier phase coding to suppress autocorrelation and cross-correlation sidelobes is evaluated, including: Acquire the radar signal with multi-carrier phase coding to suppress the autocorrelation and cross-correlation side lobes, and perform STFT transformation on the acquired radar signal to obtain: in, is the total echo signal, The radar receiving signal is a radar signal with multi-carrier phase coding that suppresses the autocorrelation and cross-correlation side lobes. is the frequency sliding window function, f is the frequency variable, is the integration variable, t is the time variable; A matched filter function is constructed based on the total echo signal; wherein the matched filter function is: in, is the matched filter function; Based on the total echo signal and the matched filter function, a pulse pressure output after intermittent sampling and forwarding interference suppression is obtained; Based on the total echo signal and the pulse pressure output after intermittent sampling and forwarding interference suppression, the signal-to-interference ratio improvement factor is obtained as follows: in, is the signal-to-interference ratio improvement factor, is the ratio of signal to interference capability, is the ratio of the peak value of the signal after matched filtering to the interference peak value.

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