Coherent spectrum synthesis of frequency-stepped chirp signal

Stepped frequency radar signal has been widely used for its high range resolution and low instantaneous bandwidth. Frequency-stepped chirp signal is a useful waveform which can decrease the frequency step number while the synthesized bandwidth remains unchanged. The spectrum synthesis method based on coherent addition is introduced to avoid the range ambiguity or "ghost" images caused by the conventional IFFT processing. In order to avoid the amplitude ripples caused by the superposition of the sub-spectrum boundaries, a spectrum synthesis method based on stitching without superposition is introduced and analyzed in detail. Besides, this method is more computational effective compared with the coherent addition method. Analysis and simulation results show that the stitching without superposition method can get a more desirable high resolution range profile than the coherent addition method and can be easily applied for its computational efficiency.