The Pulse Compression And Sidelobe Suppression For High Frequency Wave Radar

Due to electromagnetic waves in the high frequency band (between 2MHZ to 30 MHZ) in the sea surface has a characteristics of strong diffraction for the curvature of the earth, it can detect more target goals which are far away from the Earth's surface or in low altitude.This function has promoted the high-frequency research and the development of ground wave radar. In addition to the ability to detect long-range target, the radar's frequency band has made the high frequency ground wave radar also has anti-stealth capability, so it has been widely used in detecting aircraft, missiles and ships.High-frequency radar pulse compression signal processing is one of the most important signal processing means. It is defined as: the launch of the coded pulse to increase detection range and the echo signals are processed to obtain narrow pulses in order to improve the power of range resolving. Pulse compression radar system has three types of pulse signals commonly: chirp signal, nonlinear frequent modulation signals and phase modulation signals.The first chapter introduces the background of the high frequency ground wave radar,the development process of pulse compression technology and the technical achievements in sidelobe suppression of foreign scholars and so on.The second chapter describes the radar signal theory, the definition of the radar ambiguity function and the principle of pulse compression .we study Barker code, Frank code and P4 code by the definition of the radar ambiguity function, such as the autocorrelation function of the phase-coded signal and the performance of Doppler Frequency sensitivity. We also have a brief introduction of the linear frequency modulation - phase coded signals.The third chapter discusses the nature of the linear FM signal and give a brief introduction to achieve its frequency domain. Then the principle of pulse compression radar signals are simulated by matlab, including amplitude and frequency characteristics before the matched filter ,the plural envelope after the matched filter and the resolution simulation for the actual pulse compression radar systems. Then describes the issue of linear FM signal sidelobe suppression and the methods used to suppress sidelobe by windowing function. At last we discuss the impact of different sizes of Doppler frenquent shift to linear frequency modulation pulse compression signals.The fourth chapter discusses the Doppler compensation algorithm and sidelobe suppression for phase coded signal. First of all, an overview of the sidelobe signal suppression algorithm is given. And then, the minimum mean-square inverse filtering algorithm is used to suppress the sidelobe of 13, 11,and 7 Barker code. Further more , the iterative least square method is used to suppress the sidelobe of 13-bit Barker code, 16-bit Frank code and 16-bit P4 code .Both methods have achieved good results. Then the two-phase coded signal Doppler compensation method is introduced. Besides,we use interpolated Doppler compensation algorithm to compensate the Doppler frequency sidelobe for Barker code and M sequence with different signal to noise ratio. Then we calculate the peak sidelobe level and sidelobe level points. At last , the Doppler compensation is simulated for the target with several scattering center.