| Synthetic aperture radar (SAR), which is mounted on a moving platform such as unmanned aerial vehicle (UAV), aircraft and satellite, is an active high spatial resolution microwave imaging system that can operate all weather, day and night. It utilizes the relative motion between the antenna and the target area to synthesize a large ’virtual’ aperture which can generate finer along-track resolution than conventional radar. SAR has been proven to be a valuable tool in topographic mapping, marine application, military reconnaissance, water resources utilization, agriculture and forestry monitoring and geological exploration. Along with the demanding requirement of higher resolution, multiple polarization and multiple frequency band, the echo data rate soars greatly and exceeds the transfer bandwidth of the data link and the storage capacity.A data preprocessing and compression system is designed to reduce the data rate of SAR. The main achievements are as follows:(1) the state-of-arts of airborne micro-miniature radars and relevant techniques are reviewed, such as digital quadrature demodulation, digital low-pass filter, azimuth pre-filter, and BAQ compression;(2) the functional and performance requirements of micro-miniature radars are analyzed, then the structure of digital system is designed, and the functional modules are discussed, such as quadrature demodulation, azimuth pre-filter, and BAQ compression;(3) main functional modules, such as quadrature demodulation, extraction, azimuth pre-filter, and BAQ compression are designed and implemented in detail;(4) the functional modules from the working waveform and timing sequence are tested and validated, and the final imaging results are also demonstrated.The project implements raw data collection, digital quadrature demodulation, digital filtering extracting, azimuth pre-filter and BAQ compression on FPGA. It constructs a data pre-processing and data compression system, which can offer a solution for further experiments. |
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