PFDIR – A Wideband Photonic-Assisted SAR System
Ruoming Li, Wangzhe Li, Yongwei Dong, Zhilei Wen, Hanqing Zhang, Wei Sun, Jiyao Yang, Henan Zeng, Yuhui Deng, Yuchen Luan, Weidi Xu, Siwen Yang, Zhenwei Mo
Abstract
The next generation of synthetic aperture radar (SAR) systems will need transmit and receive analog signals over a wide frequency range with large bandwidth to fulfil the increasing demands. Since the performance of the digital microwave component is deteriorated at increasing frequency, radio frequency (RF) front-end with the capability of frequency conversion is needed for frequency beyond a few gigahertz. However, for the widely employed RF mixers, the inherent imperfect of I-V characteristics of nonlinear devices, generates many undesired mixing spurs, which restricts on the instantaneous bandwidth and the spurious-free dynamic range. At Aerospace Information Research Institute Chinese Academy of Sciences, a photonic-assisted front-end with functions of signal generation and deramp processing has been conceived and implemented in an experimental deramp-on-receive CW SAR system. The system is called Photonic-Assisted Front-End Deramp-on-Receive Imaging Radar and is envisaged to obtain SAR imaging at high resolution. In current stage, the Ku-band system with a bandwidth of 5.72 GHz, corresponding to a relative bandwidth of 37.8%, operates well with a fixed two-horn antenna. The configuration of the photonic front-end and the system design are described. Ground-based tests and airborne imaging results with geometrical resolution down to 5 cm are presented.