一种新型无人机高分SAR 信号非均匀混合采样技术

无人机高分辨合成孔径雷达(SAR)系统具有较大的信号频率带宽,根据奈奎斯特采样定律,雷达接收机需要超高速采样的ADC芯片。由于超高速采样率的ADC芯片的采样量化位数较低、功耗较高、成本昂贵,直接采用超高速采样ADC芯片对无人机高分辨率SAR回波信号进行采样接收不是最优方法。文中提出一种新型的非均匀混合采样技术用于对无人机高分辨率SAR回波信号进行采样接收,通过优化无人机SAR系统的信号收发时序,利用325 Msps采样率的ADC芯片即可对频率带宽为2 GHz的雷达回波信号进行采样接收,保证雷达回波的相位扰动与旁瓣电平满足应用需求。仿真实验表明:2 GHz带宽的Ku-SAR系统的回波信号能被采样率为325 Msps的ADC芯片完好采样接收,成像分辨率优于0. 2 m,旁瓣电平控制在-13 dB以下。

A Novel Non-uniform Hybrid Sampling Technology for UAV-borne High-resolution SAR Echoes

Large frequency bandwidth is the important feature of the UAV-borne high-resolution miniature synthetic aperture radar, ADC with a super high sampling rate is required for receiving the wideband echoes according to Nyquist''s sampling theorem. The real-time Nyquist sampling for wideband echoes with the super high-speed ADC is not most suitable because of the low quantization resolution, high cost and large power consumption. In this paper, a novel non-uniform hybrid sampling technology is proposed for sampling and receiving the wideband SAR echoes to reduce the requirement for the sampling rate. By optimizing the timing of the transmission and reception of SAR signals with the proposed non-uniform hybrid sampling technology, the ADCs with a sampling rate of 325 million samples per second (Msps) can meet the sampling requirement of the SAR echoes with a wideband of 2 GHz, where both the phase disturbance and side-lobes of the SAR echoes can be reduced greatly to satisfy the requirement of SAR imaging. The simulation experiment of the Ku-band SAR with a wideband of 2 GHz show that the level of the side-lobes of the SAR echoes can be reduced to below -13 dB and the imaging resolution is better than 0. 2 m.