Stepped-frequency coherent imaging of space target

Stepped-frequency pulses achieved large bandwidth using a group of pulses, thus avoiding overlarge instantaneous bandwidth of traditional radar with high resolution. It played an important part in decreasing instantaneous bandwidth and requirement to the receiver. This study aimed at analyzing all steps of stepped-frequency pulse processing and non-coherent factors for compensation. Meanwhile, it solved initial phase problem caused by special factors such as clock asynchrony in practical engineering. In stepped-frequency ISAR imaging system, non-coherent factors included phase difference between channel filters, initial phase difference between emission and receiving LO signals as well as synchronization error between initial wave gate and sampling time.