| Pulse compression of nonlinear frequency modulation (NLFM) signal is a widely used technique in weather radar applications. It can improve the range resolution.Based on the primary parameters of linear frequency modulation, this paper analyzes the effects between these parameters and pulse compression, including side-lobe suppression,the effects of Doppler frequency and signal-to-noise radio(SNR) loss. Meanwhile, it studies two theories and methods of using windows function based on phase stationary theory and S-type frequency curves to design nonlinear frequency modulation signal waveform. Respectively using combination windows method and S-type frequency curves approach method; two nonlinear frequency modulation signal waveforms are designed and their properties are analyzed. One of them has been used in a weather radar application.The main content contains three parts:Firstly, to be familiar with the fundamental theories of radar signals, the characters of linear frequency modulation signal and nonlinear frequency modulation signal is described. The characteristics of linear frequency modulation are analyzed.In the second section, it studies the theories of using combination windows method and S-type frequency modulation curves approach method to design nonlinear frequency modulation signal waveform. This paper proposed a model function to approach S-type frequency curves.Finally, a simulation experiment platform is designed and built. According to the requirements of the application, two signals are designed. Simultaneously their properties are analyzed.Besides the main work described above, the solutions of some practical issues are proposed. These analysis and computation results have direct reference value for signal waveform design. |
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