Reaearch On Adaptive Alternating Bandwidth Chirp Signals

Chirp signal is a kind of pulse-compressed signal with large time-bandwidth products achieved through linear frequency modulation. It has high resolution in range because of its great bandwidth. The radar available basically adopts the analog system to produce chirp signal. Considering the fact that the analog system is not so good as the digital system on the respect of variation of bandwidths and on the respect of switch between different bandwidths. This paper proposes to adopt the DDS(Direct Digital Synthesis) technique that produces chirp signals of different bandwidths to improve the situation of losing tracks for the ocean satellite altitude indicator in measuring coarse surfaces.This paper gives a detailed account of the waveform, matched-filter, fuzzy function, resolution in speed, resolution in range and the capacity of anti-interference of the Chirp signal. It deals with several methods to produce chirp signal and the advantages and disadvantages of these methods. It describes the working principle and performance of DDS, analyses the phase errors initiated by the phase truncation and proposes a new scheme to solve the error. Finally, a specific circuit to produce chirp signal is designed in the paper.