A RCS measurement method based on amplitude smoothing and beam gain correction

Abstract

The present invention belongs to the general technical field of radar, and relates to an RCS measurement method based on amplitude smoothing and beam gain correction. Based on the radar equation, the present invention proposes an RCS measurement formula that is easy to implement in engineering, and the bandwidth, pulse width, pulse formation and working frequency parameters are involved in the calculation, and the beam factor is corrected according to the target elevation angle to remove the influence of antenna beam gain at different elevation angles. After screening out the track sequence that does not contain zero amplitude value, starting from the third circle, five amplitude values ​​of each track time and the two circles before and after it are taken out in sequence, and a five-point cubic smoothing filter is used to obtain a smoothed amplitude value. The corrected amplitude value is used to complete the signal-to-noise ratio estimation and RCS calculation. The present invention can effectively measure the RCS value of common targets on the basis of the existing hardware platform, solves the influence of antenna beam shape and track amplitude jump, and is easy to implement in engineering.

Description

Technical Field

[0001] The invention belongs to a target parameter measurement technology in the general technical field of radar. Background Art

[0002] In the current RCS measurement method, the impact of the target deviation from the beam center on the measurement result is not taken into account. For a one-dimensional phase-scanned three-coordinate radar, the pitch is divided into multiple beams. Different targets have a certain deviation from the beam center, so the echo energy is smaller than the received signal energy calculated according to the maximum gain equal-amplitude pulse string, which will affect the accuracy of the RCS measurement value.

[0003] Signal-to-noise ratio calculation is an important part of RCS measurement. The traditional method uses the amplitude value of the current track as the effective signal amplitude for signal-to-noise ratio estimation. Due to the inherent characteristics of target flicker, the amplitude generally fluctuates by about 6 to 10 dB, resulting in excessive changes in the signal-to-noise ratio estimate and excessive fluctuations in the RCS measurement value. Summary of the invention

[0004] In order to solve the problems that the traditional method does not consider the impact of the target deviation from the beam center on the measurement result, the RCS measurement value has a large systematic error, and directly using the amplitude value of the current track as the effective signal amplitude for signal-to-noise ratio estimation will cause the signal-to-noise ratio estimation value to change too drastically and the random fluctuation of the RCS measurement value is too large, the present invention proposes an RCS measurement method based on amplitude smoothing and beam gain correction.

[0005] The present invention proposes an RCS measurement method based on amplitude smoothing and beam gain correction, and the technical solution is as follows:

[0006] Step 1: Track typical targets and collect flight paths and noise in target-free airspace as data sources;

[0007] Step 2: Count the working parameters of the one-dimensional phase-scan three-coordinate radar, including instantaneous bandwidth, pulse width, number of coherent pulses, and working frequency;

[0008] Step 3: Calculate the RCS value according to the empirical formula. The measurement formula is:

[0009] RCS0 = SNR-P t -G t -G r -cos 2 (Ele)+103+R 4 +F 2 +2·Gkx+Gjs+10-(B·τ)-n+ModifyPara (1)

[0010] All parameters are calculated in dB, including the target observation signal-to-noise ratio SNR, the transmission power Pt , transmission gain G t , receiving gain G r , target elevation angle Ele, target distance R, radar operating frequency F, one-way feeder loss Gkx, receiving mismatch loss Gjs, radar instantaneous bandwidth B, instantaneous pulse width τ, coherent pulse number n;

[0011] ModifyPara in the measurement formula is a measurement correction item. In order to solve the influence of antenna beam shape loss, the beam gain needs to be corrected, including gain correction according to the beam where the elevation angle of the track is located in the measurement formula. Therefore, the correction factor L for antenna beam shape loss is introduced. W , the calculation formula is:

[0012]

[0013]

[0014] Where m is the number of accumulated pulses, c0 is a constant, and m B The pulse received by the half-power antenna azimuth beamwidth is given by the half-power antenna azimuth beamwidth θ 0.5 , pulse repetition period T r , antenna azimuth scanning speed w and target elevation angle Ele, the correction factor value is related to the elevation angle of each track point; after obtaining the correction factor of the beam shape of each track point, it is converted into a correction value for the beam amplitude. First, the correction factor L W db is converted into linear value L W Then multiply the amplitude sequence by the linear value L W Then, it is necessary to perform amplitude smoothing estimation on the target observation signal-to-noise ratio SNR according to the actual situation.

[0015] Furthermore, the amplitude smoothing estimation of the target observation signal-to-noise ratio includes: first deleting the zero amplitude value, and then starting from the third lap track information, taking out each track time and the amplitude values ​​of the two laps before and after in turn to obtain five track amplitude information, using a five-point cubic smoothing filter for amplitude smoothing, and taking the new target amplitude value as the maximum amplitude in the data acquisition gate at the current moment to obtain a new time-amplitude sequence, and then calculating the signal-to-noise ratio.

[0016] The RCS measurement method based on amplitude smoothing and beam gain correction proposed by the present invention has the following beneficial effects:

[0017] 1: All parameters of this measurement method are known parameters in the overall radar scheme and are easy to obtain. Only radar design parameters and track files are needed to complete the real-time measurement of RCS, which is operational in engineering, improves efficiency, and saves experimental costs: Considering that beam correction can make the measurement more in line with the characteristics of this system radar and make the RCS measurement more accurate, compared with the measurement method without beam correction, the correction method can reduce the average error between the measurement result and the theoretical value by about 1.3dB.

[0018] 2: This paper solves the problem of poor estimation accuracy caused by using only the current track information for signal-to-noise ratio estimation in the traditional method. After amplitude smoothing, the comparison between the RCS value data calculated without amplitude smoothing and the original amplitude value sequence characteristics is shown. This method reduces the random fluctuations of the estimate, can effectively improve the estimation accuracy, and is simple and easy to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure is a flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further explained below in conjunction with the accompanying drawings and embodiments.

[0021] The present invention proposes an RCS measurement method based on amplitude smoothing and beam gain correction. The preferred embodiment implementation process is as follows: Figure 1 As shown, the technical solution includes:

[0022] 1: Collect the track data of different models and the noise amplitude in multiple periods of target-free airspace, and obtain the real-time target azimuth Azi, heading Course, elevation angle Ele, target distance r and track amplitude A T , Noise Amplitude A Ni .

[0023] 2: Calculate the target viewing angle based on the target's current position Azi and heading Course.

[0024] 3: Calculate the correction factor L for antenna beam shape loss using the parameters measured in steps 1 and 2 and the radar related parameters read using formulas (5) and (6): W db.

[0025] 4: For the case where the track quality is unstable and the amplitude jump is large, the amplitude zero value point is first deleted, and then the remaining amplitude sequence is smoothed by using formula (4-1) to formula (4-5) to obtain the time-amplitude sequence. It is known that the observation data at five track time points (the current time and two time points before and after) is Y -2 <Y -1<Y0 < Y1 < Y2, the five calculated results are the smoothed amplitude values at five time points obtained after five-point cubic smoothing.

[0026]

[0027]

[0028]

[0029]

[0030]

[0031] 5: Convert the correction factor L W in dB value to a linear value L W , and then multiply the amplitude sequence after amplitude smoothing obtained in step 4 by this linear value L W to obtain the corrected amplitude value.

[0032] 6: Calculate the mean value of the noise amplitude from the noise amplitudes A Ni collected in the multi-period of the target-free airspace in step 1 Then divide the time-amplitude sequence obtained after processing in step 5 by this mean value to obtain the time-signal-to-noise ratio sequence, that is, the SNR value.

[0033] 7: Calculate the real-time target scattering cross-section value after adding beam gain correction according to formula (1).

Claims

1. An RCS measurement method based on amplitude smoothing and beam gain correction, characterized in that: Step 1: Track typical targets and collect flight paths and noise in target-free airspace as data sources; Step 2: Count the operating parameters of the one-dimensional phase-scan three-coordinate radar, including instantaneous bandwidth, pulse width, number of coherent pulses, and operating frequency; Step 3: Calculate the RCS value according to the empirical formula. The measurement formula is: RCS0=SNR-P t -G t -G r -what 2 (She)+103+R 4 +F 2 +2·Gkx+Gjs+10-(B·τ)-n+ModifyPara (1) All parameters are calculated in dB, including the target observation signal-to-noise ratio SNR, the transmission power P t , transmission gain G t , receiving gain G r , target elevation angle Ele, target distance R, radar operating frequency F, one-way feeder loss Gkx, receiving mismatch loss Gjs, radar instantaneous bandwidth B, instantaneous pulse width τ, number of coherent pulses n, measurement correction term ModifyPara; perform amplitude smoothing estimation on the target observation signal-to-noise ratio SNR; The measurement correction term ModifyPara is a correction of the beam gain. The correction process includes: introducing a correction factor L for the antenna beam shape loss into the measurement formula. W , the calculation formula is: Where m is the number of accumulated pulses, c0 is a constant, and m B The pulse received by the half-power antenna azimuth beamwidth is given by the half-power antenna azimuth beamwidth θ 0.5 , pulse repetition period T r , antenna azimuth scanning speed w and target elevation angle Ele, the correction factor value is related to the elevation angle of each track point; the correction factor of the beam shape of each track point is converted into a correction value for the beam amplitude, that is, the correction factor L W db is converted into linear value L W Then multiply the linear value L by the amplitude sequence W , and obtain the corrected amplitude value; wherein the amplitude smoothing estimation process of the target observation signal-to-noise ratio SNR is as follows: For the case where the track quality is unstable and the amplitude jumps greatly, first delete the amplitude zero-value points, and then smooth the remaining amplitude sequence with formulas (4-1) to (4-5) to obtain the time-amplitude sequence. The observed data at five track time points are known as Y -2 <Y -1 <Y0 < Y1 < Y2, and the five calculated results are the smoothed amplitude values at the five time points obtained after five-point cubic smoothing. The five track time points include the current time and two time points before and after it: The correction factor L expressed in dB W db is converted into linear value L W Then multiply the smoothed amplitude sequence obtained in step 4 by the linear value L W , get the corrected amplitude value; the noise amplitude A in the target-free airspace multi-cycle collected in step 1 Ni Statistical noise amplitude mean Then, the time-amplitude sequence obtained after processing in step 5 is divided by the mean value to obtain a time-signal-to-noise ratio sequence, that is, an SNR value.

Images