A target detection method of a linear frequency modulation pulse radar
By performing a Fourier transform after mixing in a linear frequency modulated radar, the signal processing flow is simplified, the high complexity of traditional methods is solved, and the target speed and distance are measured quickly and efficiently.
Patent Information
- Application Number
- CN202211136573.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-09-19
- Publication Date
- 2026-01-27
- Estimated Expiration
- 2042-09-19
AI Technical Summary
Traditional linear frequency modulated radars have complex signal processing algorithms when measuring target velocity and distance, making it difficult to measure target information quickly and efficiently.
The system employs a multi-cycle method to mix the received signal with the transmitted waveform and then performs a fast Fourier transform. The Doppler frequency is obtained by analyzing the peak and harmonic frequencies in the signal spectrum, and the target velocity and distance information are calculated by combining the difference frequency estimation.
The signal processing is simplified, the real-time performance and accuracy of the algorithm are improved, the algorithm complexity is reduced, and the target speed and distance are measured quickly and efficiently.
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Figure CN115508820B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of radar, and more particularly to a target detection method for linear frequency modulated (LFM) pulse radar. Background Technology
[0002] Linear frequency modulated radar can use the difference frequency between the echo signal and the transmitted signal to measure the target range, but the difference frequency is also affected by the speed of the moving target, so range-Doppler coupling phenomenon will occur.
[0003] Traditional methods require two-dimensional Fourier transform processing of the echo signal, which involves complex signal processing algorithms with high computational complexity.
[0004] How to measure the speed and distance information of a target more quickly and efficiently is a topic worthy of study. Summary of the Invention
[0005] The purpose of this application is to provide a target detection method for linear frequency modulated pulse radar.
[0006] This application addresses the problem of complex signal processing algorithms and high algorithm complexity in traditional methods by simplifying the algorithm process. This application mixes the received signals and transmitted waveforms of multiple cycles of LFM radar, and then samples and performs Fourier transform on all the mixed signals.
[0007] In the radar system of this application, after the target echo is mixed with the original linear frequency modulated continuous wave, only one one-dimensional fast Fourier transform (FFT) is needed to measure the target's speed and range information.
[0008] This application is achieved through the following technical solution:
[0009] In a first aspect, this application provides a target detection method for a linear frequency modulated pulse radar, comprising:
[0010] Acquire radar transmitted signals and target echo signals;
[0011] The radar transmitted signal and the target echo signal are mixed, filtered, and sampled, and then a fast Fourier transform is performed to obtain the signal spectrum.
[0012] The Doppler frequency caused by the target motion is obtained by taking the frequency corresponding to the peak value in the signal spectrum and the harmonic frequency of the nearest transmitted signal pulse repetition frequency (hereinafter referred to as the repetition frequency), and the target velocity is calculated.
[0013] The target range information is obtained by estimating the difference frequency between the radar transmitted signal and the target echo signal. This difference frequency is then compared with the Doppler frequency to determine the difference frequency caused by the target echo range delay.
[0014] Preferably, the transmitted signal is a linear frequency modulated pulse signal generated by a signal generator, which serves as the radar transmitted signal.
[0015] Preferably, obtaining the target speed through the signal spectrum includes:
[0016] The Doppler frequency caused by the target motion is obtained based on the frequency corresponding to the peak value in the signal spectrum and the harmonic frequency of the nearest transmitted signal pulse repetition frequency. The Doppler frequency is the difference between the frequency corresponding to the peak value in the spectrum and the nearest harmonic frequency. The target velocity is then calculated based on the Doppler frequency.
[0017] Preferably, the difference frequency is estimated by analyzing the radar transmitted signal and the target echo signal. The estimated difference frequency is then used in conjunction with the Doppler frequency to obtain the difference frequency caused by the target echo range delay, and the target range information is calculated, including:
[0018] The difference frequency between the echo signal and the transmitted signal is obtained by spectrum correction, and the difference frequency caused by the echo distance delay is obtained by the Doppler frequency. The difference frequency caused by the echo distance delay is the difference between the estimated difference frequency between the echo signal and the transmitted signal and the Doppler frequency.
[0019] Preferably, the target detection method of linear frequency modulated pulse radar provided in this application has the following specific steps:
[0020] Step 1: Use a linear frequency modulated pulse signal generator to generate a radio frequency f with bandwidth B. G The frequency modulation slope is μ, and the pulse repetition frequency is f. PRF A linear frequency modulated pulse signal with a duty cycle of 50%;
[0021] Step 2: Receive multi-cycle target echo signals through the receiving antenna, and mix the echo signals with the linear frequency modulated pulse signal generated in Step 1;
[0022] Step 3: After mixing, the signal passes through a low-pass filter to obtain the difference frequency signal. The difference frequency signal is then sampled by an ADC at a sampling frequency of f. s ;
[0023] Step 4: The above sampled signal is used as input to the subsequent digital signal processor to perform FFT processing on the digital signal to obtain the spectrum;
[0024] Step 5: Extract the Doppler frequency and the difference frequency between the echo signal and the transmitted signal from the spectrum obtained in Step 4. The difference between the maximum value of the target echo signal after processing and the harmonic of its nearest pulse repetition frequency is determined as the Doppler frequency f caused by the target's velocity. d By analyzing the maximum spectral value and its location, the locations and amplitudes of the two peaks to the left and right of the maximum value, and using a spectral correction algorithm, the difference frequency signal f after processing by a frequency-mixing linear frequency modulated pulse radar is obtained.diff In linear frequency modulated pulse radar, the difference frequency f caused by the target echo range delay τ =f diff -f d ;
[0025] Step 6: Using f from step 5 τ and f d Obtain the target's velocity v and distance R.
[0026] Secondly, this application provides a target detection device for a linear frequency modulated pulse radar, comprising:
[0027] A linear frequency modulated pulse signal generator is used to transmit radar signals to targets;
[0028] A mixer is used to mix the target's transmitted signal and the echo signal;
[0029] A filter is used to filter the signal after the target's transmitted signal and the echo signal have been mixed.
[0030] ADC is used to sample mixed and filtered signals;
[0031] The Fast Fourier Transform (FFT) module is used to perform a Fast Fourier Transform on the filtered signal to obtain the signal spectrum.
[0032] The calculation module is used to obtain the target distance and velocity from the spectrum, specifically including: obtaining the Doppler frequency caused by the target motion through the frequency corresponding to the peak in the signal spectrum and the harmonic frequency of the nearest transmitted signal pulse repetition frequency, and calculating the target velocity; estimating the difference frequency between the radar transmitted signal and the target echo signal; obtaining the difference frequency caused by the target echo distance delay through the difference frequency and the Doppler frequency, and calculating the target distance information.
[0033] Thirdly, an electronic device includes: a processor and a memory communicatively connected to the processor;
[0034] The memory stores computer-executed instructions;
[0035] The processor executes computer execution instructions stored in the memory to implement the method as described in any one of the first aspects.
[0036] Fourthly, a computer program product includes a computer program that, when executed by a processor or chip, implements the method as described in any one of the first aspects.
[0037] Fifthly, this application provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the method as described in any of the first aspects.
[0038] This application has the following advantages and beneficial effects:
[0039] This application completes the target velocity and distance measurement by performing a Fourier transform on the echo, which improves the real-time performance of the algorithm while making the algorithm structure easy to implement. Attached Figure Description
[0040] The accompanying drawings, which are included to provide a further understanding of the embodiments of this application and form part of this application, do not constitute a limitation on the embodiments of this application. In the drawings:
[0041] Figure 1 This is a schematic diagram of the system principle of a linear frequency modulated pulse radar provided in an embodiment of this application.
[0042] Figure 2 This is a schematic diagram of a method for obtaining the Doppler frequency and target echo distance delay from the spectrum in an embodiment of this application.
[0043] Figure 3 This is a spectrum diagram of the positive frequency portion of the echo signal after processing in the embodiments of this application. Detailed Implementation
[0044] Before providing a detailed description of any embodiment of this application, it should be understood that the application of this application is not limited to the details of the structures shown in the following description or accompanying drawings. This application may employ other embodiments and may be implemented or performed in various ways. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive improvement are within the scope of protection of this application.
[0045] First, the multi-cycle echo signal from a linear frequency modulated radar is mixed with the transmitted signal. After a Fast Fourier Transform (FFT), peaks are formed at the pulse repetition frequency and the pulse repetition frequency harmonic position. The Doppler effect caused by a moving target shifts the peak position; this shift is the Doppler frequency. When using this spectrum to calculate the difference frequency between the received and transmitted signals, the resolution is the pulse repetition frequency, resulting in low accuracy of the difference frequency. To improve accuracy, algorithms such as spectrum correction are needed to further estimate the difference frequency.
[0046] Therefore, based on the above signal characteristics, this application proposes an efficient LFM radar target detection method, namely a target detection method for linear frequency modulated pulse radar.
[0047] The schematic diagram of a linear frequency modulated pulse radar target detection system provided in this application is as follows: Figure 1 As shown.
[0048] The specific implementation steps of this application are as follows:
[0049] Step 1: Use a linear frequency modulated pulse signal generator to generate a frequency with bandwidth B and radio frequency f. G The frequency modulation slope is μ, and the pulse repetition frequency is f. PRF A linear frequency modulated pulse signal with a duty cycle of 50%.
[0050] Step 2: Receive multi-cycle target echo signals through the receiving antenna, and mix the echo signals with the linear frequency modulated pulse signal from Step 1.
[0051] Step 3: After mixing, the signal passes through a low-pass filter to obtain the difference frequency signal. The difference frequency signal is then sampled by an ADC at a sampling frequency of f. s .
[0052] Step 4: The sampled signal is used as input to the subsequent digital signal processor. The digital signal is then processed using FFT to obtain its spectrum.
[0053] Step 5: A schematic diagram illustrating the method for extracting the Doppler frequency and the difference frequency caused by the echo distance delay from the spectrum obtained in Step 4 is shown below. Figure 2 As shown. Figure 2 In the diagram, the solid line represents the processed spectrum of a stationary target echo, and the dashed line represents the processed spectrum of a moving target echo at the same location. It can be seen that the processed echo from a stationary target forms a peak at the harmonic position of the pulse repetition frequency, with the peak value increasing closer to the true difference frequency. However, the peak position of the processed echo from a moving target shifts due to the Doppler effect. Specifically, the peak position of the echo from a target closer to the radar shifts to the right of the harmonic position, while the peak position of the echo from a target farther from the radar shifts to the left of the harmonic position. Therefore, the difference between the frequency corresponding to the maximum value of the processed target echo signal and the harmonic frequency of its nearest pulse repetition frequency is the Doppler frequency caused by the target's velocity, represented as f in the diagram. d Then, by using the maximum spectral value and its location, the locations and amplitudes of the two peaks to the left and right of the maximum value, and a spectral correction algorithm, the difference frequency signal f after processing by the mixing-based linear frequency modulated pulse radar is obtained. diff .
[0054] In this embodiment, the provided linear frequency modulated pulse signal is a linear frequency modulated pulse radar with a duty cycle of 50%. The spectrum correction method used for the linear frequency modulated pulse signal with a duty cycle of 50% is as follows: If the peak amplitude to the right of the frequency corresponding to the maximum value is greater than that to the left, the formula is:
[0055]
[0056] Conversely, the formula is:
[0057]
[0058] Among them, f max f is the frequency corresponding to the maximum value. PRF X is the pulse repetition frequency. max X represents the maximum amplitude of the spectrum. left X right These represent the spectral amplitudes at the positions corresponding to the two harmonic offsets to the left and right of the maximum value. When the duty cycle of the linear frequency modulated pulse radar is not 50%, other spectrum correction algorithms are needed to calculate f. diff The calculation logic is similar to that in this application, and will not be described again here. In linear frequency modulated pulse radar, f... diff =f τ +f d Therefore, the difference frequency f caused by the target echo range delay τ =f diff -f d .
[0059] Step 6: Using f from step 5 τ and f d The formula for obtaining the target velocity v and distance R is as follows:
[0060]
[0061]
[0062] Where c is the speed of light, μ is the frequency modulation slope, and f G This refers to the radio frequency carrier frequency.
[0063] Example:
[0064] Given a target with a distance R = 1 km, a velocity v = 50 m / s, and a signal-to-noise ratio (SNR) SNR = -10 dB, traditional linear frequency modulated (LFM) radar cannot obtain accurate velocity and distance information in a single FFT. However, the detection method proposed in this application reduces algorithm complexity and simplifies hardware structure.
[0065] Set the pulse signal repetition frequency f PRF =50kHz, the bandwidth B for generating a linear frequency modulated signal is 20MHz, and the radio frequency f G =10GHz, duty cycle 50%, pulse width 10μs. Frequency modulation slope μ = 2Bf PRF =2×10 12 echo signal sampling frequency f s=40MHz, 30 cycles of echo data are acquired in a single processing cycle. In the radar with the above parameter settings, the echo signal, after being processed by the signal processing steps of this application, obtains the spectrum as shown below. Figure 3 As shown, the frequency corresponding to the maximum spectral value is 13353.3kHz, and the offset from the nearest harmonic is 3.3kHz, which is the Doppler frequency f. d =3.3kHz, the target velocity is obtained based on the Doppler frequency. By using spectral correction and the maximum spectral value, along with the positions and amplitudes of the two peaks to the left and right of the maximum value, the frequency f of the difference frequency signal is obtained. diff =13.3333MHz. According to f diff and f d Obtain echo distance delay difference frequency f τ =f diff -f d =13.33MHz, further calculate the target distance
[0066] The results above demonstrate that the method described in this application can measure the target's velocity and distance in a single Fourier transform with minimal error, successfully reducing the complexity of the original algorithm. Furthermore, the method presented in this application has a simple structure and is easy to implement. The above example pertains to the velocity and distance detection of a single target; similar processing can be applied to the velocity and distance detection of multiple targets.
[0067] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.
Claims
1. A target detection method for linear frequency modulated pulse radar, characterized in that, include: Acquire radar transmitted signals and target echo signals; The radar transmitted signal and the target echo signal are mixed, filtered, and sampled, and then a fast Fourier transform is performed to obtain the signal spectrum. The Doppler frequency is obtained from the signal spectrum, and the target velocity is calculated. By estimating the difference frequency between the radar transmitted signal and the target echo signal, and obtaining the difference frequency caused by the target echo range delay through the difference frequency and the Doppler frequency, the target range information is calculated. The specific steps are as follows: Step 1: Use a linear frequency modulated pulse signal generator to generate a frequency with a bandwidth of B and a radio frequency. The frequency modulation slope is μ, and the pulse repetition frequency is A linear frequency modulated pulse signal with a duty cycle of 50%; Step 2: Receive multi-cycle target echo signals through the receiving antenna, and mix the echo signals with the linear frequency modulated pulse signal from Step 1; Step 3: After mixing, the signal passes through a low-pass filter to obtain the difference frequency signal. The difference frequency signal is then sampled by an ADC at a sampling frequency of [frequency value missing]. ; Step 4: The above sampled signal is used as input to the subsequent digital signal processor to perform FFT processing on the digital signal to obtain the spectrum; Step 5: Extract the Doppler frequency and the difference frequency between the echo signal and the transmitted signal from the spectrum obtained in Step 4. The difference between the frequency corresponding to the maximum value of the target echo signal after processing and the harmonic frequency of its nearest pulse repetition frequency is the Doppler frequency caused by the target's motion velocity. By analyzing the maximum spectral value and its location, the locations and amplitudes of the two peaks to the left and right of the maximum value, and using a spectral correction algorithm, the difference frequency signal value after processing by a frequency-mixing linear frequency modulated pulse radar is obtained. In linear frequency modulated pulse radar, the difference frequency caused by the target echo range delay ; Step 6: Through step 5 and Obtain the target's velocity v and distance R.
2. The method according to claim 1, characterized in that, in, The transmitted signal is a linear frequency modulated pulse signal generated by a signal generator, which is used as the radar transmission signal.
3. The method according to claim 1, characterized in that, The process of obtaining the Doppler frequency through the signal spectrum and calculating the target velocity includes: The Doppler frequency caused by the target motion is obtained based on the frequency corresponding to the peak value in the signal spectrum and the harmonic frequency of the repetition frequency of the nearest transmitted signal pulse. The Doppler frequency is the difference between the frequency corresponding to the peak value in the spectrum and the nearest harmonic frequency. The target velocity is calculated based on the Doppler frequency.
4. The method according to claim 1, characterized in that, The step of estimating the difference frequency between the radar transmitted signal and the target echo signal, obtaining the difference frequency caused by the target echo range delay through the difference frequency and the Doppler frequency, and calculating the target range information includes: The difference frequency between the echo signal and the transmitted signal is obtained by spectrum correction, and the difference frequency caused by the echo distance delay is obtained by the Doppler frequency. The difference frequency caused by the echo distance delay is the difference between the estimated difference frequency between the echo signal and the transmitted signal and the Doppler frequency.
5. A target detection device for a linear frequency modulated pulse radar, characterized in that, For implementing the method as described in any one of claims 1-4, comprising: A linear frequency modulated pulse signal generator is used to transmit radar signals to targets; A mixer is used to mix radar transmitted signals and target echo signals. A filter is used to filter the signal after the radar transmitted signal and the target echo signal are mixed. ADC samples the mixed and filtered signal; The Fast Fourier Transform (FFT) module is used to perform a Fast Fourier Transform on the filtered signal to obtain the signal spectrum. The calculation module is used to obtain the target distance and velocity from the spectrum, specifically including: obtaining the Doppler frequency caused by the target motion through the frequency corresponding to the peak in the signal spectrum and the harmonic frequency of the nearest transmitted signal pulse repetition frequency, and calculating the target velocity; estimating the difference frequency between the radar transmitted signal and the target echo signal; obtaining the difference frequency caused by the target echo distance delay through the difference frequency and the Doppler frequency, and calculating the target distance information.
6. The apparatus according to claim 5, characterized in that, It also includes an analog-to-digital converter for sampling the filtered signal and inputting it into the Fast Fourier Transform module.