Research On FMCW GB SAR System Design And Coupling Suppression Technology

Frequency modulation continuous wave(FMCW) radar system is suitable for the ground-based SAR system for slope monitoring, with the advantages of simple structure, low peak power, no blind area and high resolution. Methods of FMCW system design and methods of coupling signal analysis and canceling have been researched in this thesis. The summarizations of the work are as 1. The methodology of ground-based SAR system design under the limits of volume, weight, and power consumption is proposed for high resolution ground-based SAR. Radar system, carry frequency and waveform are chosen based on the radar performance requirements and implementation complexity. The transmit power is designed under the radiation scene. And the coherence constraints of FMCW radar including microwave oscillator, digital frequency and trig signals are proposed. The proper system isolation indicator of continuous system is specially designed for FMCW ground-based SAR imaging system. 2. The sources, transmission paths and characters of coupling signal are analyzed based on the characteristics of FMCW SAR, and the coupling signal model is established. The effect on ground-based SAR imaging by coupling signal is analyzed. The composition of phase distortion is analyzed based on radar radio frequency data acquisition by high speed oscilloscope. The influence of coupling signal is analyzed and verified through 1-d range profile and 2-d SAR image. 3. The digital coupling cancellation compression technology is studied, because of the effect for SAR image. First, the traditional digital canceling method is used to process the echo signal. Then, a new method based on singular value decomposition(SVD) to estimate cancellation reference signal in digital cancellation method is presented, for the shortcoming that reference signal can’t be updated in traditional method. Sub-arrays divided from echo matrix are used to do SVD processing to reduce the algorithm cost of time and space. The method is verified by field radar experiments.