Frequency Step Of Wideband Signals In The Altimeter Radar Applications

In air defense operation, target height information provided by altimeter radar is fundamental for threat evaluation, command decision and weapon guidance. As a kind of radar signal, which has the merit of high range resolution, the stepped-frequency signal is adopted to enhance high range measuring accuracy, and reduce the demand of digital signal processing hardware by pulse synthesis. Thus , it has great potential applications. The method of applying high range resolution to height finding, not only get the target height, but also received one dimensional range profile to complete the target identification.The definition of the stepped frequency signal is summarized firstly, and according to the radar waveform's ambiguity function, the characteristics of stepped frequency radar waveform are analyzed in detail. Then introduce the basic theory of the stepped frequency altimeter radar. Secondly, the signal processing techniques of stepped-frequency altimeter radar are discussed in detail in the paper. The signal processing methods of high range resolution based on Inverse Discrete Fourier Transform is adopted to acquire the high range resolution of the echoes. The effect on the high resolution range profile caused by the radial motion between the target and the radar is discussed. Several different velocity compensation methods based on motion parameter estimation are introduced and proved by MATLAB simulation. As the altimeter radar has a grand detection range, it can produce ambiguous range in the measurement by the PRT cycle and the redundancy of target's one dimensional range profile. After the analysis of the reason why it comes, the paper gives the resolution. Finally, the paper introduce effective angle information processing methods including monopulse angle measuring and a angular algorithm based on high resolution range profile. The performance of the latter is better than the former.