CN115542283B - Implementation method for BAQ compression of satellite-borne SAR sliding window - Google Patents
Implementation method for BAQ compression of satellite-borne SAR sliding window Download PDFInfo
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- CN115542283B CN115542283B CN202211513128.9A CN202211513128A CN115542283B CN 115542283 B CN115542283 B CN 115542283B CN 202211513128 A CN202211513128 A CN 202211513128A CN 115542283 B CN115542283 B CN 115542283B
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- 238000000638 solvent extraction Methods 0.000 claims abstract description 6
- 238000010606 normalization Methods 0.000 claims description 8
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
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Abstract
The invention provides a realization method of BAQ compression of a satellite-borne SAR sliding window, which comprises the following steps: step 1, inputting multiple paths of parallel data; step 2, partitioning the multipath parallel data in the azimuth direction in a sliding window mode; step 3, simultaneously accumulating and summing the multiple data modes in each block and dividing the sum by the number of points in the block to obtain the average value of the data modes in the block; step 4, looking up a table by using the average value of the kth-1 block to obtain the reciprocal of the standard deviation of the kth block; step 5, normalizing the data of the kth block by the inverse of the standard deviation of the kth block and carrying out quantization comparison on the normalized data; step 6, the sign bit of the multipath data and the corresponding obtained code value form a BAQ code compression result; and 7, selecting one of the compression mode results according to the control instruction and outputting the result.
Description
Technical Field
The invention belongs to the technical field of synthetic aperture radar data formers, and is mainly applied to a satellite-borne synthetic aperture radar system. The method is mainly used for calculating the amplitude mean value of radar echo data in real time in a sliding window mode, and obtaining the reciprocal of standard deviation by means of mean value table lookup to realize compression coding of the original echo data, so that SAR system performance is improved, and occupation of SAR system calculation resources is reduced.
Background
In the satellite-borne SAR system, data acquisition and processing are completed on a satellite, and then the data are transmitted to the ground for imaging. With the increase of the space-borne SAR resolution, the original echo data volume and the data rate are increased sharply, and the bandwidth of a data downloading channel is limited, so that the data volume must be reduced by adopting data compression, thereby achieving the purpose of reducing the data rate. Currently, on-board SAR achieves data compression by a block adaptive quantization algorithm (Block Adaptive Quantization, BAQ).
In the conventional spaceborne SAR system, echo data blocking in BAQ compression is realized by a recursive method. The method comprises the steps of carrying out blocking on sampled data of an original signal according to fixed sampling points and echo pulse numbers, solving an average value, then utilizing the slowly changing property of an SAR radar echo signal, determining the standard deviation of k-1 block data by using the average value of the k-1 block data, normalizing the k+1 block data by using the standard deviation of the k-1 block data, and finally quantifying and BAQ coding the normalized data of the k+1 block data.
When the amplitude mean value of the sampling signal is estimated by adopting a block-to-block recursive mode, a certain interval exists between the data adopted by calculating the mean value and the data of the standard deviation calculated by using the mean value actually, and when the statistical stability among the blocks is poor, the performance of the BAQ algorithm cannot be ensured.
Disclosure of Invention
To guarantee the performance of the BAQ compression algorithm, it is necessary to guarantee inter-block estimation performance. The embodiment of the invention provides a realization method of BAQ compression of a high-speed spaceborne SAR sliding window, which can calculate the mean value of azimuth radar echo data through a sliding window blocking method so as to ensure the performance of a BAQ algorithm.
The technical scheme of the invention is as follows: a realization method for BAQ compression of a satellite-borne SAR sliding window comprises the following steps:
step 1, inputting multiple paths of parallel data;
step 2, partitioning the multipath parallel data in a distance direction according to fixed point numbers, and partitioning the multipath parallel data in an azimuth direction in a sliding window mode;
step 3, synchronously accumulating and summing the multiple data modes in each block and dividing the sum by the number of points in the block to obtain the average value of the data modes in the block;
step 4, looking up a table by using the average value of the kth-1 block to obtain the reciprocal of the standard deviation of the kth block;
step 5, normalizing the data of the kth block by the inverse of the standard deviation of the kth block and carrying out quantization comparison on the normalized data;
step 6, the sign bit of the multipath data and the corresponding obtained code value form a BAQ code compression result;
and 7, selecting one of the compression mode results according to the control instruction and outputting the result.
The beneficial effects are that:
the method of the invention keeps partial original data to participate in mean value estimation, only partial data is updated each time, even if the statistical stability of azimuth sub-block data is poor, the sliding window processing still can obtain better algorithm performance than fixed block.
Drawings
FIG. 1 is a schematic diagram of the principle of block division of a sliding window in azimuth;
figure 2 is a flow chart of the method of the present invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and all other embodiments obtained by those skilled in the art without the inventive effort based on the embodiments of the present invention are within the scope of protection of the present invention.
In order to achieve the above object, the technical solution of the embodiment of the present invention is implemented as follows: a realization method for BAQ compression of a satellite-borne SAR sliding window comprises the following steps:
step 1, inputting multiple paths of parallel data;
step 2, partitioning the multipath parallel data in a sliding window mode according to the azimuth direction;
step 3, synchronously accumulating and summing the multiple data modes in each block and dividing the sum by the number of points in the block to obtain the average value of the data modes in the block;
step 4, looking up a table by using the average value of the kth-1 block to obtain the reciprocal of the standard deviation of the kth block;
step 5, normalizing the data of the kth block by the inverse of the standard deviation of the kth block and carrying out quantization comparison on the normalized data;
step 6, the sign bit of the multipath data and the corresponding obtained code value form a BAQ code compression result;
and 7, selecting one of the compression mode results according to the control instruction and outputting the result.
According to the embodiment of the present invention, in the step 1, for example, 16 paths of parallel data may be input to input multiple paths of parallel data;
step 2, the multipath parallel data is processed in a sliding window mode in azimuth directionProceeding withThe method comprises the following steps of:
the 16 paths of parallel data are partitioned in the azimuth direction in a sliding window mode; the size of each block is Kr multiplied by Ka, kr corresponds to the number of Kr sampling points in the distance direction, and Ka corresponds to the number of Ka echo pulses in the azimuth direction.
The sliding window block method is a method in which data between adjacent blocks in the azimuth direction has overlapping portions. Assuming that the kth-1 partition contains data from all directions from the (a-1) th direction to the (a-1) +ka) th direction, then the kth partition contains data from all directions from the (a) th direction to the (a+ka) th direction, which is the data partitioning manner of the sliding window, as shown in fig. 1.
And 3, simultaneously accumulating and summing the multiple data modes in each block and dividing the sum by the number of points in the block to obtain a data mode average value in the block, wherein the data mode average value in the block is specifically as follows:
and taking the modulus of the 16-path parallel data to obtain the modulus of the 16-path parallel data. Then, the 16 parallel data in each block are accumulated and summed simultaneously to obtain ΣA, and the sum is divided by the sampling point number of each block to obtain the average value mu=ΣA/per block data module (Kr×Ka).
Step 4, the inverse of the standard deviation of the kth block is obtained by looking up a table by using the average value of the kth-1 block;
step 5, normalizing the data of the kth block by the inverse of the standard deviation of the kth block and carrying out quantization comparison on the normalized data;
step 6, the sign bit of the multipath data and the corresponding obtained code value form a BAQ code compression result; specifically, the quantized result is subjected to BAQ coding. And selecting one of the compression mode results according to the control instruction and outputting the result.
The above-mentioned 16 paths of parallel data in each block need to open up two RAM spaces for simultaneous accumulation and summation, and respectively store the result of summing each block data in a single azimuth among Ka azimuth and the average value of Ka azimuth block data: one address space in the RAM1 correspondingly stores the accumulation result of each block of data in a single azimuth direction, each pulse echo signal updates all blocks corresponding to the oldest azimuth direction, and each Ka echo signals completely updates the RAM1 once; each address space of the RAM2 correspondingly stores the average value of the accumulated result of all the same distance-wise data in Ka azimuth echo pulses, and each azimuth is updated once.
The above-mentioned method for solving the reciprocal of standard deviation of 16 paths of parallel data in each block needs to open up a RAM space for storing the reciprocal of standard deviation corresponding to the data mean.
The above normalization of the block data is to normalize the standard deviation of the module of the block data, that is, multiply the module of the block data by the reciprocal of the standard deviation to obtain the normalization result.
The normalization result is encoded, namely, the result of the block data after standard deviation normalization is compared with a threshold level to obtain a non-uniform scalar quantization code with a contracted number of bits, and the encoding result is combined with the sign bits of the original data to form a final encoding value.
The method improves the imaging precision of the high-speed multichannel SAR system and simultaneously effectively reduces the occupation of the computing resources of the high-speed multichannel SAR system.
While the foregoing has been described in relation to illustrative embodiments thereof, so as to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, but is to be construed as limited to the spirit and scope of the invention as defined and defined by the appended claims, as long as various changes are apparent to those skilled in the art, all within the scope of which the invention is defined by the appended claims.
Claims (1)
1. The implementation method of BAQ compression of the satellite-borne SAR sliding window is characterized by comprising the following steps:
step 1, inputting multiple paths of parallel data;
step 2, partitioning the multipath parallel data in a sliding window mode according to the azimuth direction; the multi-path parallel data are 16 paths of data, the 16 paths of parallel data are partitioned in the azimuth direction in a sliding window mode, and the distance direction is partitioned in a fixed mode; the size of each block is Kr multiplied by Ka, kr corresponds to the number of Kr sampling points in the distance direction, and Ka corresponds to the number of Ka echo pulses in the azimuth direction;
the sliding window is partitioned in a way that data between adjacent partitioned blocks in the azimuth direction have overlapped parts; assuming that the kth chunk contains data from all directions from the (a-1) th direction to the (a-1) +ka) th direction, then the kth chunk contains data from all directions from the (a) th direction to the (a+ka) th direction;
step 3, synchronously accumulating and summing the multiple data modes in each block and dividing the sum by the number of points in the block to obtain the average value of the data modes in the block;
step 4, looking up a table by using the average value of the kth-1 block to obtain the reciprocal of the standard deviation of the kth block;
step 5, normalizing the data of the kth block by the inverse of the standard deviation of the kth block and carrying out quantization comparison on the normalized data;
step 6, the sign bit of the multipath data and the corresponding obtained code value form a BAQ code compression result;
step 7, selecting one of compression mode results according to the control instruction and outputting the result;
the step 3 comprises the following steps:
taking the 16 parallel data to obtain 16 parallel data modules, then accumulating and summing the 16 parallel data in each block simultaneously to obtain sigma A, dividing the sum by the sampling point number of each block to obtain the average value mu=sigma A/K of each block data module;
the step 7 comprises the following steps:
performing multi-mode BAQ coding on the quantized result to obtain coding values of various BAQ modes; selecting one of the compression mode results according to the control instruction and outputting the result;
two RAM spaces are opened up for simultaneously accumulating and summing 16 paths of parallel data in each block, and the result of summing each block data in a single azimuth direction in Ka azimuth directions and the average value of each block data in the Ka azimuth directions are respectively stored: one address space in the RAM1 correspondingly stores the accumulation result of each block of data in a single azimuth direction, each pulse echo signal updates all blocks corresponding to the oldest azimuth direction, and each Ka echo signals completely updates the RAM1 once; each address space of the RAM2 correspondingly stores the average value of the accumulation results of all the same distance data in Ka echo pulses, and the data is updated once every Ka echo pulses;
solving standard deviation of multipath parallel data in each block, opening up a RAM space for storing reciprocal of standard deviation corresponding to data mean;
the block data normalization is to normalize standard deviation of a module of the block data, namely dividing the module of the block data by the standard deviation to obtain a normalization result;
and (3) coding the normalization result, namely comparing the result of the block data subjected to standard deviation normalization with a threshold level to obtain a non-uniform scalar quantization code with a contracted number of bits, wherein the coding result is combined with the sign bits of the original data to form a final coding value.
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