Design And Implementation Of FMCW Ground-based SAR Real-time Signal Processing System Based On FPGA

In recent years,taking Field Programmable Gate Array(FPGA)as the core of radar digital processing technology has become the development trend of modern radar technology.its easy reconfiguration characteristics and abundant Intellectual Property(IP)core resources,plus excellent clock management module,high-speed parallel pipeline structure and flexible place & route capacity exactly meets the requirements of high-precision,high-quality and high-real-time performance of modern radar technology.Among the many kinds of radars,Frequency Modulated Continuous Wave(FMCW)-based ground-based Synthetic Aperture Radar(SAR)or slope monitoring radar is the main research subject of this paper.It is a two-dimensional SAR image that uses a ground-based antenna to move uniformly on a horizontal track to form an azimuth synthetic aperture to acquire the target area.And then through the antenna multiple reciprocating heavy rail motion obtain the continuous 2D SAR data of the target area,so that the geology of the target area can be continuously monitored to achieve real-time early warning of the landslide disaster.The digital processing part of the slope monitoring radar relies on the FPGA + Digital Signal Processor(DSP)heterogeneous platform to realize the ground-based SAR two-dimensional data processing.The FPGA plays an important role in data acquisition and transmission and data preprocessing.But the Derchiping technique for FMCW and the Back Project(BP)algorithm for omnidirectional time-domain focusing imaging are used in the range and azimuth directions respectively.Although the final two-dimensional information processing results of the radar have high signal-to-noise ratio and imaging quality,However,there is a problem that the overall system data transmission volume and calculation amount are huge,and the algorithm runs for a long time and the efficiency is low.In order to solve these problem,this article specifically designed "FPGA-based FMCW radar real-time signal processing system",which is the use of FPGA composed of digital hardware to achieve real-time processing of echo signals.In the early stage,the theoretical verification and imaging processing of Dechirping technology and BP algorithm are done through MATLAB;In the mid-term,the real-time processing software system is designed and implemented through RAM/ROM,Divider,FFT IP core in Xilinx ISE 14.7 development platform,and is co-simulated with Modelsim 10.0 to verify the completeness and correctness of the real-time processing module function after the test algorithm transplanted;Later,through the joint debugging of the radar digital system development board and the Chipscope software,the real-time processing capability is verified in practical applications.Through the above research methods,real-time digital signal processing operations based on FMCW generation,AD dynamic phase modulation acquisition and control,echo multiple coherent accumulation,Hanning window filtering,and distance compression are successfully implemented.It has been proved by several experiments that DA can generate 1.6GHz FM continuous wave through Direct Digital Write Frequency Synthesizers(DDWS),and AD can acquire completely coherent echo waveform after dynamic phase modulation,and it also realizes fast processing of 128 frames 16×2 bit 48000 point real-time echo data of any multiple of coherent accumulation in 37.25 ms,Hanning window filtering and distance compression calculation,at the same time the data compression rate of up to 99.2%.After Hanning window filtering,can reduce the side spot To-31.54 dB.So far,the FPGA-based FMCW radar real-time signal processing system designed in this paper has successfully reduced the data operation pressure and transmission pressure of the lower-level computer in the ground-based SAR system,and completed the radar echo signal Real-time pre-processing work before the radar echo data reaches the DSP.