A FPGA implementation method of SAR echo data pre-filtering technology

Abstract

The invention relates to an FPGA implementation method of the SAR echo data pre-filtering technology, which belongs to the technical field of radar imaging and the technical field of digital signal processing. The method includes the following steps: 1. Determine the order of the filter; 2. Store the echo data in the DDR in the form of a two-dimensional matrix, wherein the size of the two-dimensional matrix is ​​the filter order multiplied by the number of points in a distance direction. When the number of pulses is greater than the order of the filter, the previous echo data is overwritten from the starting position of the matrix; 3. When a pulse data is stored, use a fast algorithm to find the sum of the elements in the current matrix, which is the output of the first-order filter ; 4. Taking the output of the first-order filter as input, repeat steps 2 and 3 to form a second-stage filter; 5. Sampling the output of the second-stage filter in proportion to output and storing it in another block of DDR. The invention can realize high-speed processing of SAR echo data, realize the effect of pre-filtering, and lay a foundation for the real-time performance of SAR imaging processing.

Description

technical field [0001] The invention relates to an FPGA (Field Programmable Gate Array) implementation method of SAR echo data pre-filtering technology, which belongs to the technical field of radar imaging and the technical field of digital signal processing. Background technique [0002] The pulse repetition frequency (PRF) of synthetic aperture radar (SAR) is limited, and its lower limit is determined by the Doppler bandwidth of the echo signal. When the SAR works in the pulse state, the received Doppler echo signal is in the form of sampling. In order to ensure that the sampled signal does not lose the information carried, according to Shannon's sampling theorem, the sampling rate must be greater than the bandwidth B of the original signal d ,Right now [0003] PRF≥B d (1) [0004] This is the lower bound of the PRF. [0005] In order to image the entire target area, the SAR beam needs to irradiate the target area multiple times, which requires that the flight dist...

AI Technical Summary

Problems solved by technology

In order to detect short-distance targets, the pulse width needs to be reduced, and reducing the pulse width will inevitably lead to a reduction in the average power of the transmitted signal

In order to ensure sufficient average transmit power, PRF must be increased, but this means that the amount of echo data increases, and the subsequent processing and storage modules will not be able to bear it

Direct sampling operation will cause noise spectrum aliasing, resulting in a decrease in image signal-to-noise ratio, so a low-pass filter must be used for preprocessing before imaging processing

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