Radar speed measurement method based on gain control

Abstract

The invention relates to the technical field of radar speed measurement, and discloses a radar speed measurement method based on gain control, comprising the following steps: S1, system initialization and gain calibration: pre-testing loop stability; s2, signal transmitting and echo receiving: transmitting and receiving a dynamic gain control echo signal; s3, high-speed signal acquisition and synchronization: acquiring I / Q channel data; s4, Doppler processing and dynamic gain compensation: Doppler frequency is extracted; s5, Doppler peak value detection and speed calculation: detecting a target peak value, and calculating a target speed; s6, dynamic performance verification: carrying out a multi-target scene test and an anti-interference test; s7, boundary condition robustness test: carrying out extreme environment test and overload recovery test; and S8, calibrating and outputting data. Through real-time gain compensation of digital automatic gain control and robust Doppler processing, high-precision speed measurement can still be realized under the conditions of strong clutter, interference and rapid gain change, the stability is good, and the influence of the environment is small.

Description

Technical Field

[0001] This invention relates to the field of radar speed measurement technology, specifically a radar speed measurement method based on gain control. Background Technology

[0002] Radar speed measurement primarily uses the Doppler effect to measure vehicle speed and is widely used in traffic management. For example, radar speed detectors, used by police, can accurately detect speeding and record license plate information, enabling 24 / 7 monitoring in conjunction with mobile enforcement or fixed monitoring systems. Gain control, on the other hand, is an important signal processing technique. Its main function is to control the gain of the transmitted signal in different scenarios to maintain a certain signal level. In radar systems, gain control determines the radar receiver's ability to detect weak signals; it can improve radar sensitivity, optimize performance, and avoid interference.

[0003] A Chinese patent discloses a radar speed measurement method based on gain control (authorization announcement number CN105911545B). This patented technology adds an automatic digital gain adjustment stage to the traditional radar speed measurement signal processing process and adjusts the amplitude of the amplified reflected wave signal to be located near the center line of the antenna pattern. This minimizes the measurement error caused by the beam angle of the radar microwave antenna and improves the accuracy of radar speed measurement. However, it does not verify the radar test under different conditions, which may lead to test distortion and cannot guarantee the stability of the test. Summary of the Invention

[0004] The purpose of this invention is to provide a radar velocity measurement method based on gain control to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A radar velocity measurement method based on gain control includes the following steps: S1. System initialization and gain calibration: Start the radar system, load the pre-calibrated parameters, and verify whether they meet the design requirements; then perform a pre-test on loop stability. S2. Signal Transmission and Echo Reception: First, the radar transmitter generates and transmits a highly stable radio frequency pulse signal according to the set parameters. Then, the radar receiving antenna captures the dynamic gain control echo signal reflected from the target. S3. High-speed signal acquisition and synchronization: High-speed analog-to-digital converter is used to synchronously acquire I / Q channel data and capture the transient response of the receiver chain at the moment of gain switching to analyze signal distortion. S4. Doppler Processing and Dynamic Gain Compensation: Perform Doppler-dimensional FFT on each range gate to extract the target's velocity information, i.e., the Doppler frequency; record the real-time gain value of each pulse; perform inverse gain correction on the signal amplitude before Doppler-dimensional FFT; and use interpolation to recover the spectrum for overloaded range gates. S5. Doppler peak detection and velocity calculation: First, the target peak is detected in the compensated Doppler spectrum, then the target velocity is calculated, and the phase difference method is used to improve the resolution of low-speed targets. S6. Dynamic Performance Verification: Multi-target scenario testing and anti-interference testing are conducted separately. The multi-target scenario testing is used to verify the radar's resolution capability and dynamic range management when strong and weak targets coexist. The anti-interference testing is used to verify the radar's survivability and signal fidelity under strong interference. S7. Boundary condition robustness test: Extreme environment test and overload recovery test are performed respectively. The extreme environment test is used to verify the functional integrity, performance stability and reliability of the receiver; the overload recovery test is used to verify the receiver's anti-saturation capability and fast recovery characteristics. S8. Calibration and Data Output: The automatic gain control curve is updated periodically using the built-in test signal, and the target speed value and confidence index are output periodically.

[0006] As a further aspect of the present invention: in step S1, the specific steps for system initialization and gain calibration are as follows: S11. Load pre-calibration parameters: Start the radar system, load the calibration parameters of digital automatic gain control, and verify whether the gain range and step accuracy meet the design requirements. S12. Loop stability pre-test: Inject a step signal, measure the settling time and overshoot of the gain loop, and sweep the frequency to test the loop phase margin.

[0007] As a further aspect of the present invention: in step S2, the dynamic gain control echo reception stage is divided into a sensitivity time control stage and an automatic gain control stage, wherein, The sensitivity time control stage is used to handle large-scale range attenuation; the specific processing method is as follows: the detection range is divided into N range gates; then, the gain value of each gate is independently configured to suppress short-range clutter saturation and amplify the echo of long-range targets; The automatic gain control stage is used to handle inter-pulse fluctuations. The specific processing method is as follows: First, the received signal strength indication voltage is output through the logarithmic amplifier. Then, the sampling root mean square of the analog signal within the pulse is calculated to realize dynamic updating of the gain according to the target signal strength, so that the signal is stabilized in the optimal quantization range of automatic gain control and the target echo strength is avoided from changing with the environment.

[0008] As a further aspect of the present invention: in step S4, the method for extracting the target velocity information is as follows: S41. Assume that the radar transmits N pulses, and each pulse collects M range gates to form an M×N matrix; S42. For each range gate, input the complex signal of the corresponding N pulses and perform an N-point Doppler FFT along the slow time dimension; this generates N Doppler frequency units for each range gate, forming an M×N range-Doppler matrix, thus extracting the target's velocity information.

[0009] As a further aspect of the present invention: in step S5, the specific method for target peak detection is as follows: S51, Zero-frequency clutter suppression: Identify the zero-frequency region in the Doppler spectrum, set a symmetrical notch filter band centered on the zero frequency; then force the spectral amplitude within the notch band to zero, and retain the effective Doppler spectrum on both sides outside the notch band; S52. Doppler spectrum normalization processing: Perform logarithmic transformation on the spectrum after notch filtering, perform background average power estimation, and then subtract the background average value from the entire spectrum. S53. Two-dimensional constant false alarm rate target detection: The detection window slides in the range-Doppler plane; the detection threshold is calculated using an ordered statistical method. When the power of the window to be tested is greater than the detection threshold, it is determined to be the target peak value.

[0010] As a further aspect of the present invention: in step S6, the multi-target scene testing is implemented as follows: S61. Synchronized strong and weak target echo signals are generated at a fixed distance using a radar simulator; S62. Receive and record the raw echo data of multiple cycles, turn off automatic gain control, and repeat the test as a control group; S63. Perform constant false alarm rate (CFAR) detection on each frame of data and record whether weak targets are detected.

[0011] As a further aspect of the present invention: in step S7, during extreme environment testing, steps S2 to S6 are repeated under a set temperature cycle to check whether the temperature drift is less than the set value. In the overload recovery test, an overload pulse is injected to check whether the receiver recovery time and speed measurement accuracy loss are less than the set value.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves radar speed measurement by sequentially performing system initialization and gain calibration, signal transmission and echo reception, high-speed signal acquisition and synchronization, Doppler processing and dynamic gain compensation, Doppler peak detection and velocity calculation, dynamic performance verification, and boundary condition robustness testing. Through real-time gain compensation with digital automatic gain control and robust Doppler processing, it ensures high-precision speed measurement under conditions of strong clutter, interference, and rapid gain changes, exhibiting good stability and minimal susceptibility to environmental influences. Detailed Implementation

[0013] In this embodiment of the invention, a radar velocity measurement method based on gain control includes the following steps: S1. System Initialization and Gain Calibration: Start the radar system, load the pre-calibrated parameters, and verify whether they meet the design requirements, providing a stable, controllable, and predictable starting point for subsequent adaptive gain control and speed measurement algorithms; then conduct a loop stability pre-test to ensure that the system will not go out of control when facing extreme scenarios, such as sudden strong targets or vehicles approaching rapidly without oscillation, saturation, or response lag. S2. Signal Transmission and Echo Reception: First, the radar transmitter generates and transmits a highly stable radio frequency pulse signal according to set parameters, such as phase noise < -100dBc / Hz @1kHz; then, the radar receiving antenna captures the dynamic gain control echo signal reflected from the target; the dynamic gain control echo reception stage is divided into sensitivity time control (STC stage) and automatic gain control (AGC stage), wherein... The sensitivity time control stage is used to handle large-scale distance attenuation, such as millisecond-level updates. The specific processing method is as follows: the detection range is divided into N range gates, such as 1024 gates; then, the gain value of each gate is configured independently, such as by loading a preset curve through a DAC to suppress short-range clutter saturation. Short-range clutter, such as ground clutter, sea clutter, and interference waves, reduces the short-range gain by 20-40dB, which can effectively prevent strong clutter from blocking the link and amplify the echo of the long-range target. Since the propagation loss of the long-range target echo is inversely proportional to the fourth power of the distance, the long-range gain is increased by 30dB to avoid the long-range target echo being extremely weak due to propagation loss, which can effectively amplify the weak target signal. The automatic gain control (AGC) stage is used to handle inter-pulse fluctuations, such as microsecond-level responses. The specific processing method is as follows: First, the received signal strength indicator voltage (RSSI voltage) is output through a logarithmic amplifier. Then, the root mean square (RMS) of the analog signal within the pulse is calculated. This allows for dynamic gain updates based on the target signal strength, stabilizing the signal within the optimal quantization range of AGC, such as -1 dBFS. This prevents the target echo strength from changing with environmental factors such as target fluctuations, interference, and atmospheric attenuation. S3. High-speed signal acquisition and synchronization: High-speed analog-to-digital converters are used to synchronously acquire I / Q channel data. The I / Q channel data is a complex form that efficiently represents the complete information of the bandpass signal in the baseband. It consists of in-phase components (I) and quadrature components (Q), which are generated by quadrature downconversion. The transient response of the receiver chain at the moment of gain switching is captured. If a strong target appears at the moment of gain switching, the signal distortion is analyzed. S4. Doppler Processing and Dynamic Gain Compensation: Perform a Doppler-dimensional FFT (Fast Fourier Transform) on each range gate to extract the target's velocity information, i.e., the Doppler frequency; record the real-time gain value of each pulse; perform inverse gain correction on the signal amplitude before the Doppler-dimensional FFT; and use interpolation to recover the spectrum for overloaded range gates, such as matrix completion based on SVD. S5. Doppler peak detection and velocity calculation: First, the target peak is detected in the compensated Doppler spectrum, then the target velocity is calculated, and the phase difference method is used to improve the resolution of low-speed targets. S6. Dynamic Performance Verification: Multi-target scenario testing and anti-interference testing are conducted separately. The multi-target scenario testing is used to verify the radar's resolution capability and dynamic range management when strong and weak targets coexist. The anti-interference testing is used to verify the radar's survivability and signal fidelity under strong interference. S7. Boundary condition robustness test: Extreme environment test and overload recovery test are performed respectively. The extreme environment test is used to verify the functional integrity, performance stability and reliability of the receiver; the overload recovery test is used to verify the receiver's anti-saturation capability and fast recovery characteristics. In extreme environment testing, steps S2 to S6 are repeated under a set temperature cycle to check whether the temperature drift is less than the set value; for example, in extreme environment testing at -35℃ to +85℃, the temperature drift is checked to be less than ±0.5dB. In the overload recovery test, an overload pulse is injected to check whether the receiver recovery time and speed measurement accuracy loss are less than the set values; for example, injecting a +20dB overload pulse checks whether the receiver recovery time is less than 5μs and the speed measurement accuracy loss is less than 5%. S8. Calibration and Data Output: The built-in test signal is used to periodically update the automatic gain control curve to counteract environmental time-varying factors and maintain the long-term accuracy of the receiver link; and the target velocity value and confidence index, such as spectral signal-to-noise ratio and gain fluctuation variance, are output periodically to maintain the accuracy of the test.

[0014] Preferably, in step S1, the specific steps for system initialization and gain calibration are as follows: S11. Loading Pre-calibration Parameters: Start the radar system and load the calibration parameters for the digital automatic gain control (AGC). These parameters include the sensitivity-time control curve, the automatic gain control law, and the gain-voltage mapping table. During the loading of the sensitivity-time control curve, read the range-gain mapping table (e.g., R=0km: 30dB; R=10km: 60dB) and print the first 10 range gate gain values. During the loading of the automatic gain control law, import the input power-gain relationship (e.g., the design value K=90dB) and plot the P_in vs Gain curve (i.e., the characteristic of the amplifier's gain as a function of input power). During the loading of the gain-voltage mapping table, load the DAC code-amplifier gain correspondence table (e.g., the 12-bit DAC code, i.e., the digital input value to the digital-to-analog converter (DAC)) and check if the DAC code is continuous without jumps. Verify that the gain range and step accuracy meet the design requirements. The gain range includes the minimum gain and the maximum gain (e.g., -20dB~). +10dB; step accuracy such as 0.1dB; S12. Loop stability pre-test: Inject a step signal and measure the settling time and overshoot of the gain loop. If the settling time is <1μs and the overshoot is <5%, then sweep the frequency to test the loop phase margin. If the loop phase margin is >45°, then the loop phase margin is >45°.

[0015] Preferably, in step S4, the method for extracting target velocity information is as follows: S41. Assume that the radar transmits N pulses, and each pulse collects M range gates to form an M×N matrix; S42. Input the complex signal of N pulses corresponding to each range gate, i.e., the I / Q data sequence; perform N-point Doppler FFT along the slow time dimension; so that each range gate generates N Doppler frequency units, forming an M×N range-Doppler matrix, i.e., extract the target's velocity information.

[0016] Preferably, in step S5, the specific method for target peak detection is as follows: S51. Zero-frequency clutter suppression: Identify the zero-frequency region in the Doppler spectrum, set a symmetrical notch filter band with the zero frequency as the center; then force the spectral amplitude within the notch band to zero, retain the effective Doppler spectrum on both sides outside the notch band, so as to eliminate the floor rise caused by ground clutter and expose the masked slow targets. S52. Doppler spectrum normalization processing: Perform logarithmic transformation on the spectrum after notch filtering, perform background average power estimation, and then subtract the background average value from the entire spectrum to standardize the spectrum baseline and eliminate the remaining clutter gradient. S53. Two-dimensional constant false alarm rate target detection: The detection window slides in the range-Doppler plane; the detection threshold is calculated using an ordered statistical method, and when the power of the window to be tested is greater than the detection threshold, it is determined to be the target peak value; In step S5, the formula for calculating the target velocity is... ,in, For Doppler frequency shift; The wavelength of the emitted wave.

[0017] Preferably, in step S6, the multi-target scenario testing is implemented as follows: S61. Synchronize strong and weak target echo signals at a fixed distance using a radar simulator; for example, set the strong target at 10km with a signal-to-clutter ratio (SCR) of 60dB, and the weak target at 10km+10m. S62. Receive and record raw echo data for multiple cycles, such as ≥200 frames of raw echo data; turn off automatic gain control and repeat the test as a control group; S63. Perform constant false alarm rate (CFAR) detection on each frame of data and record whether weak targets are detected.

[0018] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A radar velocity measurement method based on gain control, characterized in that, Includes the following steps: S1. System initialization and gain calibration: Start the radar system, load the pre-calibrated parameters, and verify whether they meet the design requirements; then perform a pre-test on loop stability. S2. Signal Transmission and Echo Reception: First, the radar transmitter generates and transmits a highly stable radio frequency pulse signal according to the set parameters. Then, the radar receiving antenna captures the dynamic gain control echo signal reflected from the target. S3. High-speed signal acquisition and synchronization: High-speed analog-to-digital converter is used to synchronously acquire I / Q channel data and capture the transient response of the receiver chain at the moment of gain switching to analyze signal distortion. S4. Doppler Processing and Dynamic Gain Compensation: Perform Doppler-dimensional FFT on each range gate to extract the target's velocity information, i.e., the Doppler frequency; record the real-time gain value of each pulse; perform inverse gain correction on the signal amplitude before Doppler-dimensional FFT; and use interpolation to recover the spectrum for overloaded range gates. S5. Doppler peak detection and velocity calculation: First, the target peak is detected in the compensated Doppler spectrum, then the target velocity is calculated, and the phase difference method is used to improve the resolution of low-speed targets. S6. Dynamic Performance Verification: Multi-target scenario testing and anti-interference testing are conducted separately. The multi-target scenario testing is used to verify the radar's resolution capability and dynamic range management when strong and weak targets coexist. The anti-interference testing is used to verify the radar's survivability and signal fidelity under strong interference. S7. Boundary condition robustness test: Extreme environment test and overload recovery test are performed respectively. The extreme environment test is used to verify the functional integrity, performance stability and reliability of the receiver; the overload recovery test is used to verify the receiver's anti-saturation capability and fast recovery characteristics. S8. Calibration and Data Output: The automatic gain control curve is updated periodically using the built-in test signal, and the target speed value and confidence index are output periodically.

2. The radar velocity measurement method based on gain control according to claim 1, characterized in that, In step S1, the specific steps for system initialization and gain calibration are as follows: S11. Load pre-calibration parameters: Start the radar system, load the calibration parameters of digital automatic gain control, and verify whether the gain range and step accuracy meet the design requirements. S12. Loop stability pre-test: Inject a step signal, measure the settling time and overshoot of the gain loop, and sweep the frequency to test the loop phase margin.

3. The radar velocity measurement method based on gain control according to claim 1, characterized in that, In step S2, the dynamic gain control echo reception stage is divided into sensitivity time control and automatic gain control stages, wherein... The sensitivity time control stage is used to handle large-scale range attenuation; the specific processing method is as follows: the detection range is divided into N range gates; then, the gain value of each gate is independently configured to suppress short-range clutter saturation and amplify the echo of long-range targets; The automatic gain control stage is used to handle inter-pulse fluctuations. The specific processing method is as follows: First, the received signal strength indication voltage is output through the logarithmic amplifier. Then, the sampling root mean square of the analog signal within the pulse is calculated to realize dynamic updating of the gain according to the target signal strength, so that the signal is stabilized in the optimal quantization range of automatic gain control and the target echo strength is avoided from changing with the environment.

4. The radar velocity measurement method based on gain control according to claim 1, characterized in that, In step S4, the method for extracting target velocity information is as follows: S41. Assume that the radar transmits N pulses, and each pulse collects M range gates to form an M×N matrix; S42. For each range gate, input the complex signal of the corresponding N pulses and perform an N-point Doppler FFT along the slow time dimension; this generates N Doppler frequency units for each range gate, forming an M×N range-Doppler matrix, thus extracting the target's velocity information.

5. The radar velocity measurement method based on gain control according to claim 1, characterized in that, In step S5, the specific method for target peak detection is as follows: S51, Zero-frequency clutter suppression: Identify the zero-frequency region in the Doppler spectrum, set a symmetrical notch filter band centered on the zero frequency; then force the spectral amplitude within the notch band to zero, and retain the effective Doppler spectrum on both sides outside the notch band; S52. Doppler spectrum normalization processing: Perform logarithmic transformation on the spectrum after notch filtering, perform background average power estimation, and then subtract the background average value from the entire spectrum. S53. Two-dimensional constant false alarm rate target detection: The detection window slides in the range-Doppler plane; the detection threshold is calculated using an ordered statistical method. When the power of the window to be tested is greater than the detection threshold, it is determined to be the target peak value.

6. The radar velocity measurement method based on gain control according to claim 1, characterized in that, In step S6, the multi-target scenario testing is implemented as follows: S61. Synchronized strong and weak target echo signals are generated at a fixed distance using a radar simulator; S62. Receive and record the raw echo data of multiple cycles, turn off automatic gain control, and repeat the test as a control group; S63. Perform constant false alarm rate (CFAR) detection on each frame of data and record whether weak targets are detected.

7. The radar velocity measurement method based on gain control according to claim 1, characterized in that, In step S7, during the extreme environment test, steps S2 to S6 are repeated under a set temperature cycle to check whether the temperature drift is less than the set value. In the overload recovery test, an overload pulse is injected to check whether the receiver recovery time and speed measurement accuracy loss are less than the set value.