Research On Velocity Measurement And Performance Of Synthetic Wideband Radar

Velocity measurement is one of the important aspects in wideband radar signal processing. Synthetic wideband radar employing coherent train of jumped-frequency pulses is widely used for its high Doppler resolution. The inherent delay-Doppler coupling of stepped-frequency signal is the key problem in velocity measurement with wideband radar. In this paper the principles of velocity measurement through parameter design and waveform design with the wideband signal are analyzed respectively. Then the processing measures and their performances are validated and compared by simulating with MATLAB.Firstly, the uniform ambiguity function of the coherent train of jumped-frequency pulses is deduced, which is used to analyze the impact of the signal parameters on the ambiguity and resolution characteristics. The ambiguity functions of stepped-frequency signal,Costas-coded jumped-frequency signal and random jumped-frequency signal are discussed to analyze the ambiguity and resolution characteristics of them.Secondly, the Doppler performance of HPRF stepped-frequency radar signal is analyzed and its parameter design principle is given. By calculating the phasic difference and analyzing the waveform of frequency domain, the range ambiguity is resolved to get the range of each scatter center, from which we can obtain the precise velocity by resolving the range-velocity coupling. Simulation results prove that this radar scheme can simultaneously achieve unambiguous velocity and high range resolution, and analyzing the waveform of frequency domain based on matched-filter which is brought forward in this paper can improve the precision of the range measurement as well as the velocity measurement.Thirdly, based on waveform design, two kinds of jumped-frequency radar signals which have thumbtack-shaped ambiguity function - Costas-coded and random jumped-frequency signals are analyzed respectively. Then the STRETCH processing method is improved for high velocity targets on the occasion of wideband Costas-coded jumped-frequency signal, which can resolve high-sidelobe problem effectively. What's more, the sidelobes of the two signals are analyzed and the reduction methods are given correspondingly. By simulating with MATLAB we compare the velocity measurement and high range resolution profile of the two signals, which indicates that the Costas-Ordered stepped-frequency signal has better performance.Finally, the coherent train of jumped-frequency pulses is combined with linear frequency modulated pulses to form the coherent train of jumped-frequency LFM pulses, whose processing measures are modified and extended. The waveform and parameter selecting principle of the coherent train of jumped-frequency LFM pulses is summed up, and simulations are performed with respect to the project requirement.