Sar radar two-dimensional antenna pattern measurement method, system, medium, and device

Abstract

The present application belongs to the field of radar measurement, and particularly relates to a SAR radar two-dimensional antenna pattern measurement method, system, medium and equipment. The present application realizes the measurement of the radar two-dimensional antenna pattern based on the passive corner reflector mode, arranges a column of corner reflectors in the range width of the radar, acquires corresponding original echo data and internal calibration data, then performs pulse compression processing on the internal calibration data and the original echo data, performs amplitude correction on the amplitude maximum value after pulse compression, combines the geometric relationship to obtain the two-dimensional discrete antenna pattern of each corner reflector under different downward angles and different azimuth angles within a synthetic aperture time, then performs fitting and normalization processing on the two-dimensional discrete antenna pattern data of all corner reflectors to obtain the two-dimensional transmitting antenna pattern under the radar central downward angle and the zero azimuth angle. The processing method can realize accurate measurement of the radar two-dimensional antenna pattern by using the original echo data containing the passive corner reflector, and effectively reduce the measurement cost.

Description

Technical Field

[0001] This invention belongs to the field of radar measurement, and particularly relates to methods, systems, media and equipment for measuring the radiation pattern of two-dimensional antennas of SAR radar. Background Technology

[0002] Synthetic Aperture Radar (SAR) two-dimensional antenna Figure 1 Measurements are typically conducted in an anechoic chamber to obtain the theoretical two-dimensional antenna pattern of the radar. However, the actual two-dimensional antenna pattern of airborne / spaceborne SAR radar is affected by factors such as the operating environment and changes in antenna component performance, which can alter the radar beam pointing and consequently affect the overall performance of the radar system. Most current methods for measuring the two-dimensional antenna pattern of synthetic aperture radar (SAR) are based on SAR image data containing passive corner reflectors (obtained by processing raw radar echo data using high-precision imaging algorithms). This method (referred to as the first type of method) obtains the two-dimensional antenna pattern by comprehensively processing the characteristics of the corner reflector in the SAR image and the positional relationship between the corner reflector and the radar. However, this method requires first processing the raw echo data to obtain the SAR image, resulting in relatively low time efficiency. In addition, there is also a method based on active corner reflectors (referred to as the second type of method) to obtain the two-dimensional transmission antenna pattern of the radar. This method uses active corner reflectors to receive the original radar echo data, and then processes it to obtain the two-dimensional transmission antenna pattern. However, active corner reflectors are expensive, and it is difficult to deploy multiple active corner reflectors (more than 5) in a single calibration test to accurately measure the two-dimensional transmission antenna pattern of the radar. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method, system, medium and equipment for measuring the radiation pattern of a two-dimensional antenna of a SAR radar.

[0004] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for measuring the radiation pattern of a two-dimensional antenna for SAR radar, comprising:

[0005] Step 1: Acquire data from each corner reflector placed according to preset conditions in real time, and process the internal calibration data in each data to obtain the internal calibration time delay corresponding to each corner reflector.

[0006] Step 2: Using the first GPS time as a reference, read the first raw echo data from each data point within a time period that differs from the first GPS time by a preset time. The first GPS time is the time when the distance between each corner reflector and the radar GPS position is the minimum.

[0007] Step 3: Perform range pulse compression processing on each pulse moment based on the first raw echo data, and calculate the range range of the raw echo data pulse compressed for each corner reflector based on the minimum distance between each corner reflector and the radar within the time period and the internal calibration time delay corresponding to each corner reflector.

[0008] Step 4: Obtain the maximum amplitude value of each corner reflector at each pulse moment after range pulse compression processing within each distance range, and perform slant range correction on each maximum amplitude value to obtain the correction data corresponding to each corner reflector. Based on the viewing angle, azimuth angle and correction data of each pulse of the corner reflector in the antenna coordinate system, determine the discrete antenna pattern of any corner reflector within the synthetic aperture time, until the discrete antenna pattern of all corner reflectors within the synthetic aperture time is determined. Fit all discrete antenna patterns to obtain a two-dimensional antenna pattern, and complete the measurement based on the two-dimensional antenna pattern.

[0009] The beneficial effects of this invention are as follows: This invention achieves the measurement of radar two-dimensional antenna radiation patterns based on passive corner reflectors. By deploying a row of corner reflectors along the radar range width, corresponding raw echo data and internal calibration data are acquired. Then, pulse compression processing is performed on the internal calibration data and raw echo data, and amplitude correction is performed on the maximum amplitude value after pulse compression. Combining geometric relationships, the two-dimensional discrete antenna radiation patterns of each corner reflector under different downward viewing angles and different azimuth angles within a synthetic aperture time are obtained. Then, the two-dimensional discrete antenna radiation pattern data of all corner reflectors are fitted and normalized to obtain the two-dimensional transmitting antenna radiation pattern under the radar center downward viewing angle and zero azimuth angle. This processing method can achieve accurate measurement of radar two-dimensional antenna radiation patterns using raw echo data containing passive corner reflectors while effectively reducing measurement costs.

[0010] Based on the above technical solution, the present invention can be further improved as follows.

[0011] Furthermore, the corner reflectors placed according to preset conditions specifically refer to:

[0012] A row of corner reflectors is deployed on the ground along the radar's range.

[0013] Furthermore, the specific steps for processing the internal calibration data in each data set to obtain the internal calibration time delay corresponding to each corner reflector are as follows:

[0014] Range pulse compression processing is performed on each internal calibration data and the reference internal calibration signal to obtain the pulse compression signal corresponding to each internal calibration data. The internal calibration time delay corresponding to each internal calibration data is calculated based on the time corresponding to the maximum value of the pulse compression signal, the signal pulse width of the internal calibration data, and the signal minimum delay of the internal calibration data. The internal calibration time delay corresponding to each internal calibration data is determined as the internal calibration time delay corresponding to each corner reflector.

[0015] Furthermore, the specific steps of fitting all discrete antenna patterns to obtain a two-dimensional antenna pattern are as follows:

[0016] By fitting and normalizing all discrete antenna patterns, two-dimensional antenna patterns at the center down-view angle and at zero azimuth angle are obtained.

[0017] Another technical solution of the present invention to solve the above-mentioned technical problems is as follows: A SAR radar two-dimensional antenna pattern measurement system, comprising:

[0018] The acquisition module is used to: acquire data collected by each corner reflector placed according to preset conditions in real time, and process the internal calibration data in each data to obtain the internal calibration time delay corresponding to each corner reflector;

[0019] The first calculation module is used to: read the first raw echo data in each data within a time period that differs from the first GPS time by a preset time, with the first GPS time as a reference, where the first GPS time is the time when the distance between each corner reflector and the radar GPS position is the minimum.

[0020] The second calculation module is used to: perform range pulse compression processing on each pulse moment based on the first raw echo data, and calculate the range range of the raw echo data pulse compressed for each corner reflector based on the minimum distance between each corner reflector and the radar within the time period and the internal calibration time delay corresponding to each corner reflector.

[0021] The measurement module is used to: acquire the maximum amplitude value of each corner reflector at each pulse moment after range pulse compression processing within each distance range, and perform slant range correction on each maximum amplitude value to obtain the correction data corresponding to each corner reflector; determine the discrete antenna pattern of any corner reflector within the synthetic aperture time based on the viewing angle, azimuth angle and correction data of each pulse of the corner reflector in the antenna coordinate system, until the discrete antenna pattern of all corner reflectors within the synthetic aperture time is determined; fit all discrete antenna patterns to obtain a two-dimensional antenna pattern; and complete the measurement based on the two-dimensional antenna pattern.

[0022] The beneficial effects of this invention are as follows: This invention achieves the measurement of radar two-dimensional antenna radiation patterns based on passive corner reflectors. By deploying a row of corner reflectors along the radar range width, corresponding raw echo data and internal calibration data are acquired. Then, pulse compression processing is performed on the internal calibration data and raw echo data, and amplitude correction is performed on the maximum amplitude value after pulse compression. Combining geometric relationships, the two-dimensional discrete antenna radiation patterns of each corner reflector under different downward viewing angles and different azimuth angles within a synthetic aperture time are obtained. Then, the two-dimensional discrete antenna radiation pattern data of all corner reflectors are fitted and normalized to obtain the two-dimensional transmitting antenna radiation pattern under the radar center downward viewing angle and zero azimuth angle. This processing method can achieve accurate measurement of radar two-dimensional antenna radiation patterns using raw echo data containing passive corner reflectors while effectively reducing measurement costs.

[0023] Furthermore, the corner reflectors placed according to preset conditions specifically refer to:

[0024] A row of corner reflectors is deployed on the ground along the radar's range.

[0025] Furthermore, the specific steps for processing the internal calibration data in each data set to obtain the internal calibration time delay corresponding to each corner reflector are as follows:

[0026] Range pulse compression processing is performed on each internal calibration data and the reference internal calibration signal to obtain the pulse compression signal corresponding to each internal calibration data. The internal calibration time delay corresponding to each internal calibration data is calculated based on the time corresponding to the maximum value of the pulse compression signal, the signal pulse width of the internal calibration data, and the signal minimum delay of the internal calibration data. The internal calibration time delay corresponding to each internal calibration data is determined as the internal calibration time delay corresponding to each corner reflector.

[0027] Furthermore, the specific steps of fitting all discrete antenna patterns to obtain a two-dimensional antenna pattern are as follows:

[0028] By fitting and normalizing all discrete antenna patterns, two-dimensional antenna patterns at the center down-view angle and at zero azimuth angle are obtained.

[0029] Another technical solution of the present invention to solve the above-mentioned technical problems is as follows: a storage medium storing instructions, wherein when a computer reads the instructions, the computer executes the method described in any of the above-mentioned methods.

[0030] The beneficial effects of this invention are as follows: This invention achieves the measurement of radar two-dimensional antenna radiation patterns based on passive corner reflectors. By deploying a row of corner reflectors along the radar range width, corresponding raw echo data and internal calibration data are acquired. Then, pulse compression processing is performed on the internal calibration data and raw echo data, and amplitude correction is performed on the maximum amplitude value after pulse compression. Combining geometric relationships, the two-dimensional discrete antenna radiation patterns of each corner reflector under different downward viewing angles and different azimuth angles within a synthetic aperture time are obtained. Then, the two-dimensional discrete antenna radiation pattern data of all corner reflectors are fitted and normalized to obtain the two-dimensional transmitting antenna radiation pattern under the radar center downward viewing angle and zero azimuth angle. This processing method can achieve accurate measurement of radar two-dimensional antenna radiation patterns using raw echo data containing passive corner reflectors while effectively reducing measurement costs.

[0031] Another technical solution of the present invention to solve the above-mentioned technical problems is as follows: an electronic device, including the above-mentioned storage medium and a processor that executes the instructions in the above-mentioned storage medium.

[0032] The beneficial effects of this invention are as follows: This invention achieves the measurement of radar two-dimensional antenna radiation patterns based on passive corner reflectors. By deploying a row of corner reflectors along the radar range width, corresponding raw echo data and internal calibration data are acquired. Then, pulse compression processing is performed on the internal calibration data and raw echo data, and amplitude correction is performed on the maximum amplitude value after pulse compression. Combining geometric relationships, the two-dimensional discrete antenna radiation patterns of each corner reflector under different downward viewing angles and different azimuth angles within a synthetic aperture time are obtained. Then, the two-dimensional discrete antenna radiation pattern data of all corner reflectors are fitted and normalized to obtain the two-dimensional transmitting antenna radiation pattern under the radar center downward viewing angle and zero azimuth angle. This processing method can achieve accurate measurement of radar two-dimensional antenna radiation patterns using raw echo data containing passive corner reflectors while effectively reducing measurement costs. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating an embodiment of a SAR radar two-dimensional antenna pattern measurement method according to the present invention.

[0034] Figure 2 This is a structural framework diagram provided for an embodiment of a SAR radar two-dimensional antenna pattern measurement system of the present invention;

[0035] Figure 3 This is a complete flowchart illustrating an embodiment of a SAR radar two-dimensional antenna pattern measurement method according to the present invention.

[0036] Figure 4 This is a schematic diagram of the corner reflector layout provided in an embodiment of the SAR radar two-dimensional antenna pattern measurement method of the present invention;

[0037] Figure 5 This is a schematic diagram of the "minimum" distance position provided in an embodiment of a SAR radar two-dimensional antenna pattern measurement method of the present invention;

[0038] Figure 6 This is a schematic diagram of the discrete antenna pattern of the i-th corner reflector provided in an embodiment of the SAR radar two-dimensional antenna pattern measurement method of the present invention;

[0039] Figure 7 This is a schematic diagram of the SAR two-dimensional transmitting antenna pattern measurement results provided in an embodiment of the SAR radar two-dimensional antenna pattern measurement method of the present invention. Detailed Implementation

[0040] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0041] like Figure 1 As shown, a method for measuring the radiation pattern of a two-dimensional antenna in a SAR radar includes:

[0042] Step 1: Acquire data from each corner reflector placed according to preset conditions in real time, and process the internal calibration data in each data to obtain the internal calibration time delay corresponding to each corner reflector.

[0043] Step 2: Using the first GPS time as a reference, read the first raw echo data from each data point within a time period that differs from the first GPS time by a preset time. The first GPS time is the time when the distance between each corner reflector and the radar GPS position is the minimum.

[0044] Step 3: Perform range pulse compression processing on each pulse moment based on the first raw echo data, and calculate the range range of the raw echo data pulse compressed for each corner reflector based on the minimum distance between each corner reflector and the radar within the time period and the internal calibration time delay corresponding to each corner reflector.

[0045] Step 4: Obtain the maximum amplitude value of each corner reflector at each pulse moment after range pulse compression processing within each distance range, and perform slant range correction on each maximum amplitude value to obtain the correction data corresponding to each corner reflector. Based on the viewing angle, azimuth angle and correction data of each pulse of the corner reflector in the antenna coordinate system, determine the discrete antenna pattern of any corner reflector within the synthetic aperture time, until the discrete antenna pattern of all corner reflectors within the synthetic aperture time is determined. Fit all discrete antenna patterns to obtain a two-dimensional antenna pattern, and complete the measurement based on the two-dimensional antenna pattern.

[0046] In some possible implementations, this invention uses passive corner reflectors to measure the radar's two-dimensional antenna pattern. A row of corner reflectors is deployed across the radar's range swath to acquire corresponding raw echo data and internal calibration data. The internal calibration data and raw echo data are then pulse-compressed, and the maximum amplitude value after pulse compression is corrected. Combined with geometric relationships, the two-dimensional discrete antenna pattern for each corner reflector at different downward viewing angles and azimuth angles within a synthetic aperture time is obtained. Finally, the two-dimensional discrete antenna pattern data from all corner reflectors are fitted and normalized to obtain the two-dimensional transmitting antenna pattern at the radar's center downward viewing angle and zero azimuth angle. This processing method can achieve accurate measurement of the radar's two-dimensional antenna pattern using raw echo data containing passive corner reflectors while effectively reducing measurement costs.

[0047] It should be noted that, as Figure 3 As shown, the method includes:

[0048] S1, a row of corner reflectors is deployed on the ground along the radar range width. Airborne / spaceborne SAR acquires raw echo data, internal calibration data, and time and location information of the radar GPS, including the ground corner reflectors, and at the same time measures the accurate position of each ground corner reflector.

[0049] First, a row of corner reflectors is deployed on the ground along the radar swath width (see schematic diagram). Figure 4 (As shown), and measure the accurate position of each ground corner reflector; secondly, the airborne / spaceborne SAR radar acquires raw echo data, internal calibration data, and radar GPS time and location information containing ground corner reflectors, providing data support for subsequent processing.

[0050] It should be noted that the internal calibration data is the internal calibration signal obtained by the radar through the radar's internal calibration network after the reference internal calibration signal is processed. It is used to monitor the performance of the radar system and obtain the time delay of the signal passing through the radar's internal system.

[0051] It should be noted that the time and location information of the radar GPS are as follows: the time range is the time range of the airborne radar illumination including the flight path of the ground corner reflector, or the time range of the power on and off before and after the satellite radar illumination including the ground corner reflector; the radar GPS location information is the three-dimensional coordinate information of the radar.

[0052] S2 processes internal calibration data and obtains the internal calibration time delay.

[0053] Range pulse compression is performed using the radar-acquired internal calibration signal and a reference internal calibration signal. The time t0 corresponding to the maximum value of the pulse compression result is obtained. Then, the pulse width T of the internal calibration signal is used as the basis for the calculation. s_inner Minimum delay T of internal calibration signal d_inner The internal calibration time delay t1 is obtained from parameters such as time.

[0054] It should be noted that this step is to determine the signal transmission delay within the radar equipment, and to compensate for this delay when subsequently determining the range of the corner reflector.

[0055] Meanwhile, assuming that the pulse compression occurs at the midpoint of the internal calibration signal pulse width, the internal calibration time delay t1 is...

[0056] t1 = t0 + T d_inner -T s_inner / twenty one)

[0057] If the pulse compression is performed at the initial position of the internal calibration signal pulse width, and the internal calibration time delay t1 is...

[0058] t1 = t0 + T d_inner (2)

[0059] S3, each corner reflector is rotated to the same coordinate system as the radar GPS position, the distance between the current corner reflector and the GPS position at different times is calculated, and the GPS time corresponding to the "minimum" distance is determined.

[0060] First, using the radar position as a reference, the position information of each corner reflector is transformed to ensure that the coordinate systems of the two are consistent. Second, the distance between the radar position and the current corner reflector at each pulse moment is calculated, and the GPS time t corresponding to the "minimum" distance is obtained. med .

[0061] It should be noted that converting the corner reflector's position information to the radar's position coordinate system unifies the coordinates of the two systems, making it easier to calculate the distance between them. Generally, the radar's position coordinate system can be considered as a geocentric coordinate system (referred to as a local coordinate system), while the position information measured by the corner reflector is in a geographic coordinate system (longitude-latitude-altitude format). Therefore, latitude and longitude can be directly converted to the geocentric coordinate system.

[0062] In addition, the "minimum" distance R dop This refers to the radar's range at zero Doppler, as illustrated in the diagram. Figure 5 As shown, when the radar slant angle is When the formula is as follows:

[0063]

[0064] S4. Using the GPS time as the midpoint, expand outwards by one synthetic aperture time interval to read the raw echo data within that time interval.

[0065] At this GPS time t med Using the central time point as the reference, and extending outwards by one synthetic aperture time before and after it, the time range for determining the two-dimensional antenna pattern measurement of the current corner reflector is [t]. min ,tmax ].

[0066] It should be noted that extending the synthetic aperture time by one unit before and after is to obtain a complete synthetic aperture time for the radar illuminating the current corner reflector. The synthetic aperture time can be determined based on the radar wavelength λ and the radar velocity V. r Radar antenna length D, shortest distance R between radar and angular reflection min The time to synthesize the aperture is estimated and calculated using the following formula:

[0067]

[0068] S5 calculates the distance between the radar and the current corner reflector at each pulse moment within this time period.

[0069] For the current corner reflector, determine the time range [t]. min ,t max The distance between the radar position and the corner reflector at each pulse moment of the internal radar.

[0070] It should be noted that the time update rate of each pulse of the original radar echo is higher than the update frequency of the radar position obtained by post-differential analysis. Therefore, in this step, the radar position needs to be interpolated by time so that it corresponds to the time of each pulse of the original radar echo.

[0071] S6, range pulse compression is performed on each pulse moment of the original echo during this time period. Based on the current "minimum" distance between the corner reflector and the radar and the internal calibration time delay, the approximate range of the original echo data pulse compression corresponding to the current corner reflector is obtained.

[0072] For the current corner reflector, within this time range, range pulse compression is performed on the original echo signal and the radar reference signal at each radar pulse moment to obtain the pulse compression signal of each pulse in all range directions within this time range. This is then combined with the "minimum" distance R between the current corner reflector and the radar. dop Internal calibration time delay t1, radar raw echo data sampling start time t s Find the range of distances corresponding to the pulse compression of the current corner reflector within this time range.

[0073] It should be noted that, firstly, based on the minimum distance R... dop Determine the corresponding distance pixel Nr dop Then according to Nr dop By taking a certain range up and down, we obtain the corresponding range in the distance direction. Assume the speed of light is C, and the radar modulation frequency is F. s At this time, we have:

[0074] Nr dop =(R dop -t1·C / 2-ts ·C / 2) / F s (5)

[0075] The range can be in Nr dop Based on the radar SAR resolution and other parameters, combined with empirical values, a certain number of pixels are taken before and after the range range [Nr] is obtained. dop -ΔNr,Nr dop +ΔNr] ensures that the peak pulse compression of the corner reflector within the range direction during the synthetic aperture time. For airborne radar, ΔNr is taken as an empirical value between 60 and 100; for spaceborne radar, ΔNr is taken as an empirical value between 120 and 200.

[0076] Similarly, assuming the reference signal for each radar pulse is s(t), the time delay between the radar and the corner reflector is T, and the amplitude modulation signal is s′(*), then the signal obtained after the radar illuminates the corner reflector is s′(tT). FFT represents a fast Fourier transform operation on the signal, and IFFT represents a fast inverse Fourier transform operation. Therefore, the signal after range pulse compression of the original radar echo signal is:

[0077] F(t)=IFFT(FFT(s(t))·FFT(s′(tT))) (6)

[0078] S7, within this distance range, calculate the maximum amplitude of each pulse after pulse compression at the current corner reflector point;

[0079] Within the time and distance range of the current corner reflector, determine the maximum amplitude of the signal after each pulse distance pulse compression.

[0080] It should be noted that the signal F(t) after pulse compression for each pulse is a function of the slant distance. To obtain the maximum amplitude value, F(t) can be interpolated to find the maximum amplitude value Amax. ij and the corresponding slope distance R ij (i represents the i-th corner reflector, and j represents the j-th pulse moment).

[0081] S8, perform slant range correction on the maximum amplitude after pulse compression at each moment of the current corner reflector point;

[0082] Within the time and range range of the current corner reflector, the maximum value of the signal amplitude after each pulse compression is slant range corrected to obtain the sampled value of the discrete antenna pattern of the current corner reflector.

[0083] It should be noted that, according to the radar equations, the relationship between the antenna pattern and the pulse compression amplitude and slant range is as follows:

[0084]

[0085] Among them, G 2 (θ i ) represents the antenna pattern function of the i-th corner reflector and the j-th pulse; θ ij Let α be the incident angle in the radar antenna coordinate system corresponding to the j-th pulse moment of the i-th corner reflector; ij R is the azimuth angle in the radar antenna coordinate system corresponding to the j-th pulse time of the i-th corner reflector; Amax is the maximum amplitude value of the i-th corner reflector at the j-th pulse time; R ij σ represents the distance between the i-th corner reflector and the radar at the j-th pulse moment; i Let be the RCS value of the i-th corner reflector.

[0086] Similarly, the slant distance correction step corrects the above formula to obtain the correction value.

[0087] S9. Based on the geometric relationship, the downward angle and azimuth of each pulse of the corner reflector in the antenna coordinate system are obtained. Combined with the data after the maximum amplitude slant range correction after pulse compression of each pulse of the corner reflector, the discrete antenna pattern of the current corner reflector synthetic aperture time is obtained.

[0088] First, the downward viewing angle and azimuth angle of the current corner reflector at each pulse moment in the radar antenna coordinate system are obtained based on geometric relationships. Second, combined with the data of the current corner reflector after slant range correction, the discrete antenna pattern of the corner reflector within one synthetic aperture time is obtained.

[0089] It should be noted that the distance from the radar to the corner reflector calculated at each pulse moment is based on the local coordinate system. At this time, it is necessary to transform the distance vector from the radar to the corner reflector at each pulse moment to the radar antenna coordinate system through coordinate transformation to obtain the three-dimensional coordinates in the radar antenna coordinate system. Then, the downward viewing angle and azimuth angle in the radar antenna coordinate system are obtained based on the three-dimensional coordinates. At this point, the angle information in formula (7) has been completely established. Combined with the current corner reflector data after slant range correction, the discrete antenna pattern data of the corner reflector in one synthetic aperture time is obtained.

[0090] Similarly, for a corner reflector, θ in its discrete antenna pattern data over a synthetic aperture time interval ij The change is relatively small, α ij The variation is relatively large (because it covers a full synthetic aperture time).

[0091] Figure 6 The diagram shows a discrete antenna pattern obtained by the i-th corner reflector, with the black dashed lines representing discrete sampling points.

[0092] S10. Based on this method, the discrete antenna patterns of all corner reflectors are obtained. The two-dimensional discrete antenna patterns of all corner reflectors are fitted to obtain the two-dimensional antenna pattern at the center downward viewing angle, thereby realizing the measurement of the two-dimensional antenna pattern of SAR radar.

[0093] First, perform operations S3 to S9 as described in the manual for each corner reflector to obtain antenna pattern data of all corner reflectors in the radar antenna coordinate system. Second, perform fitting (three-dimensional surface fitting) and normalization processing on the two-dimensional discrete antenna pattern data of all corner reflectors to obtain two-dimensional antenna patterns at the center downward viewing angle and zero azimuth angle, thereby realizing the measurement of the two-dimensional antenna pattern of SAR radar.

[0094] Figure 7 The diagram shows a discrete antenna pattern obtained by the i-th corner reflector. The thick black solid line represents the measurement results of the two-dimensional (range and azimuth) antenna pattern of the SAR radar.

[0095] It should be noted that since the corner reflectors are initially deployed in columns, most of the corner reflectors will obtain the "minimum" distance at the same orientation. Therefore, step S4 is omitted when processing the remaining corner reflectors.

[0096] Preferably, in any of the above embodiments, the corner reflector placed according to preset conditions specifically refers to:

[0097] A row of corner reflectors is deployed on the ground along the radar's range.

[0098] Preferably, in any of the above embodiments, the process of processing the internal calibration data in each data set to obtain the internal calibration time delay corresponding to each corner reflector specifically involves:

[0099] Range pulse compression processing is performed on each internal calibration data and the reference internal calibration signal to obtain the pulse compression signal corresponding to each internal calibration data. The internal calibration time delay corresponding to each internal calibration data is calculated based on the time corresponding to the maximum value of the pulse compression signal, the signal pulse width of the internal calibration data, and the signal minimum delay of the internal calibration data. The internal calibration time delay corresponding to each internal calibration data is determined as the internal calibration time delay corresponding to each corner reflector.

[0100] Preferably, in any of the above embodiments, the step of fitting all discrete antenna patterns to obtain a two-dimensional antenna pattern specifically involves:

[0101] By fitting and normalizing all discrete antenna patterns, two-dimensional antenna patterns at the center down-view angle and at zero azimuth angle are obtained.

[0102] like Figure 2 As shown, a SAR radar two-dimensional antenna pattern measurement system includes:

[0103] The acquisition module 100 is used to: acquire data collected by each corner reflector placed according to preset conditions in real time, and process the internal calibration data in each data to obtain the internal calibration time delay corresponding to each corner reflector;

[0104] The first calculation module 200 is used to: read the first raw echo data in each data within a time period that differs from the first GPS time by a preset time, with the first GPS time as a reference, wherein the first GPS time is the time when the distance between each corner reflector and the radar GPS position is the minimum.

[0105] The second calculation module 300 is used to: perform range pulse compression processing on each pulse moment based on the first original echo data, and calculate the range range of the original echo data pulse compressed for each corner reflector based on the minimum distance between each corner reflector and the radar within the time period and the internal calibration time delay corresponding to each corner reflector.

[0106] The measurement module 400 is used to: acquire the maximum amplitude value of each corner reflector at each pulse moment after range pulse compression processing within each distance range, and perform slant range correction on each maximum amplitude value to obtain the correction data corresponding to each corner reflector; determine the discrete antenna pattern of any corner reflector within the synthetic aperture time based on the viewing angle, azimuth angle and correction data of each pulse of the corner reflector in the antenna coordinate system, until the discrete antenna pattern of all corner reflectors within the synthetic aperture time is determined; fit all discrete antenna patterns to obtain a two-dimensional antenna pattern; and complete the measurement based on the two-dimensional antenna pattern.

[0107] In some possible implementations, this invention uses passive corner reflectors to measure the radar's two-dimensional antenna pattern. A row of corner reflectors is deployed across the radar's range swath to acquire corresponding raw echo data and internal calibration data. The internal calibration data and raw echo data are then pulse-compressed, and the maximum amplitude value after pulse compression is corrected. Combined with geometric relationships, the two-dimensional discrete antenna pattern for each corner reflector at different downward viewing angles and azimuth angles within a synthetic aperture time is obtained. Finally, the two-dimensional discrete antenna pattern data from all corner reflectors are fitted and normalized to obtain the two-dimensional transmitting antenna pattern at the radar's center downward viewing angle and zero azimuth angle. This processing method can achieve accurate measurement of the radar's two-dimensional antenna pattern using raw echo data containing passive corner reflectors while effectively reducing measurement costs.

[0108] Preferably, in any of the above embodiments, the corner reflector placed according to preset conditions specifically refers to:

[0109] A row of corner reflectors is deployed on the ground along the radar's range.

[0110] Preferably, in any of the above embodiments, the process of processing the internal calibration data in each data set to obtain the internal calibration time delay corresponding to each corner reflector specifically involves:

[0111] Range pulse compression processing is performed on each internal calibration data and the reference internal calibration signal to obtain the pulse compression signal corresponding to each internal calibration data. The internal calibration time delay corresponding to each internal calibration data is calculated based on the time corresponding to the maximum value of the pulse compression signal, the signal pulse width of the internal calibration data, and the signal minimum delay of the internal calibration data. The internal calibration time delay corresponding to each internal calibration data is determined as the internal calibration time delay corresponding to each corner reflector.

[0112] Preferably, in any of the above embodiments, the step of fitting all discrete antenna patterns to obtain a two-dimensional antenna pattern specifically involves:

[0113] By fitting and normalizing all discrete antenna patterns, two-dimensional antenna patterns at the center down-view angle and at zero azimuth angle are obtained.

[0114] Another technical solution of the present invention to solve the above-mentioned technical problems is as follows: a storage medium storing instructions, wherein when a computer reads the instructions, the computer executes the method described in any of the above-mentioned methods.

[0115] In some possible implementations, this invention uses passive corner reflectors to measure the radar's two-dimensional antenna pattern. A row of corner reflectors is deployed across the radar's range swath to acquire corresponding raw echo data and internal calibration data. The internal calibration data and raw echo data are then pulse-compressed, and the maximum amplitude value after pulse compression is corrected. Combined with geometric relationships, the two-dimensional discrete antenna pattern for each corner reflector at different downward viewing angles and azimuth angles within a synthetic aperture time is obtained. Finally, the two-dimensional discrete antenna pattern data from all corner reflectors are fitted and normalized to obtain the two-dimensional transmitting antenna pattern at the radar's center downward viewing angle and zero azimuth angle. This processing method can achieve accurate measurement of the radar's two-dimensional antenna pattern using raw echo data containing passive corner reflectors while effectively reducing measurement costs.

[0116] Another technical solution of the present invention to solve the above-mentioned technical problems is as follows: an electronic device, including the above-mentioned storage medium and a processor that executes the instructions in the above-mentioned storage medium.

[0117] In some possible implementations, this invention uses passive corner reflectors to measure the radar's two-dimensional antenna pattern. A row of corner reflectors is deployed across the radar's range swath to acquire corresponding raw echo data and internal calibration data. The internal calibration data and raw echo data are then pulse-compressed, and the maximum amplitude value after pulse compression is corrected. Combined with geometric relationships, the two-dimensional discrete antenna pattern for each corner reflector at different downward viewing angles and azimuth angles within a synthetic aperture time is obtained. Finally, the two-dimensional discrete antenna pattern data from all corner reflectors are fitted and normalized to obtain the two-dimensional transmitting antenna pattern at the radar's center downward viewing angle and zero azimuth angle. This processing method can achieve accurate measurement of the radar's two-dimensional antenna pattern using raw echo data containing passive corner reflectors while effectively reducing measurement costs.

[0118] Readers should understand that in the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0119] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the method embodiments described above are merely illustrative. For instance, the division of steps is only a logical functional division, and there may be other division methods in actual implementation. For example, multiple steps may be combined or integrated into another step, or some features may be ignored or not executed.

[0120] If the above methods are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0121] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for measuring the radiation pattern of a two-dimensional antenna in a SAR radar, characterized in that, include: Step 1: Acquire data from each corner reflector placed according to preset conditions in real time, and process the internal calibration data in each data to obtain the internal calibration time delay corresponding to each corner reflector. Step 2: Using the first GPS time as a reference, read the first raw echo data from each data point within a time period that differs from the first GPS time by a preset time. The first GPS time is the time when the distance between each corner reflector and the radar GPS position is the minimum. Step 3: Perform range pulse compression processing on each pulse moment based on the first raw echo data, and calculate the range range of the raw echo data pulse compressed for each corner reflector based on the minimum distance between each corner reflector and the radar within the time period and the internal calibration time delay corresponding to each corner reflector. Step 4: Obtain the maximum amplitude value of each corner reflector at each pulse moment after range pulse compression processing within each distance range, and perform slant range correction on each maximum amplitude value to obtain the correction data corresponding to each corner reflector. Based on the viewing angle, azimuth angle and correction data of each pulse of the corner reflector in the antenna coordinate system, determine the discrete antenna pattern of any corner reflector within the synthetic aperture time, until the discrete antenna pattern of all corner reflectors within the synthetic aperture time is determined. Fit all discrete antenna patterns to obtain a two-dimensional antenna pattern, and complete the measurement based on the two-dimensional antenna pattern.

2. The SAR radar two-dimensional antenna pattern measurement method according to claim 1, characterized in that, The corner reflectors placed according to preset conditions are specifically: A row of corner reflectors is deployed on the ground along the radar's range.

3. The SAR radar two-dimensional antenna pattern measurement method according to claim 1, characterized in that, The specific steps for processing the internal calibration data in each data set to obtain the internal calibration time delay for each corner reflector are as follows: Range pulse compression processing is performed on each internal calibration data and the reference internal calibration signal to obtain the pulse compression signal corresponding to each internal calibration data. The internal calibration time delay corresponding to each internal calibration data is calculated based on the time corresponding to the maximum value of the pulse compression signal, the signal pulse width of the internal calibration data, and the signal minimum delay of the internal calibration data. The internal calibration time delay corresponding to each internal calibration data is determined as the internal calibration time delay corresponding to each corner reflector.

4. The SAR radar two-dimensional antenna pattern measurement method according to claim 1, characterized in that, The specific steps for fitting all discrete antenna patterns to obtain a two-dimensional antenna pattern are as follows: By fitting and normalizing all discrete antenna patterns, two-dimensional antenna patterns at the center down-view angle and at zero azimuth angle are obtained.

5. A SAR radar two-dimensional antenna pattern measurement system, characterized in that, include: The acquisition module is used to: acquire data collected by each corner reflector placed according to preset conditions in real time, and process the internal calibration data in each data to obtain the internal calibration time delay corresponding to each corner reflector; The first calculation module is used to: read the first raw echo data in each data within a time period that differs from the first GPS time by a preset time, with the first GPS time as a reference, where the first GPS time is the time when the distance between each corner reflector and the radar GPS position is the minimum. The second calculation module is used to: perform range pulse compression processing on each pulse moment based on the first raw echo data, and calculate the range range of the raw echo data pulse compressed for each corner reflector based on the minimum distance between each corner reflector and the radar within the time period and the internal calibration time delay corresponding to each corner reflector. The measurement module is used to: acquire the maximum amplitude value of each corner reflector at each pulse moment after range pulse compression processing within each distance range, and perform slant range correction on each maximum amplitude value to obtain the correction data corresponding to each corner reflector; determine the discrete antenna pattern of any corner reflector within the synthetic aperture time based on the viewing angle, azimuth angle and correction data of each pulse of the corner reflector in the antenna coordinate system, until the discrete antenna pattern of all corner reflectors within the synthetic aperture time is determined; fit all discrete antenna patterns to obtain a two-dimensional antenna pattern; and complete the measurement based on the two-dimensional antenna pattern.

6. The SAR radar two-dimensional antenna pattern measurement system according to claim 5, characterized in that, The corner reflectors placed according to preset conditions are specifically: A row of corner reflectors is deployed on the ground along the radar's range.

7. A SAR radar two-dimensional antenna pattern measurement system according to claim 5, characterized in that, The specific steps for processing the internal calibration data in each data set to obtain the internal calibration time delay for each corner reflector are as follows: Range pulse compression processing is performed on each internal calibration data and the reference internal calibration signal to obtain the pulse compression signal corresponding to each internal calibration data. The internal calibration time delay corresponding to each internal calibration data is calculated based on the time corresponding to the maximum value of the pulse compression signal, the signal pulse width of the internal calibration data, and the signal minimum delay of the internal calibration data. The internal calibration time delay corresponding to each internal calibration data is determined as the internal calibration time delay corresponding to each corner reflector.

8. A SAR radar two-dimensional antenna pattern measurement system according to claim 5, characterized in that, The specific steps for fitting all discrete antenna patterns to obtain a two-dimensional antenna pattern are as follows: By fitting and normalizing all discrete antenna patterns, two-dimensional antenna patterns at the center down-view angle and at zero azimuth angle are obtained.

9. A storage medium, characterized in that, The medium stores instructions that, when read by a computer, cause the computer to execute the method as described in any one of claims 1 to 4.

10. An electronic device, characterized in that, Includes the storage medium of claim 9 and a processor that executes instructions within the storage medium.

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