Wideband Digital Array Of Digital Delay And Phase Shift,

Wideband Digital Array Radar (WDAR) is a fully digitized array antenna radar in which wideband signal waveform is transmitted and digital beamforming (DBF) technology is used in receiving and transmitting. Compared with conventional narrowband phased array radar, true time delay is used in wideband digital array to replace the phase shift. In order to compensate the channel dispersed delay accurately, fractional delay filter (FDF) is introduced. In this dissertation, the wideband digital beamforming is investigated in detail.First of all, A receiver structure based on wideband radar signal with carrier is proposed through analyzing a FDF design method and the principle of wideband digital beamforming.Then, three FDF design methos are described including windowing the ideal impulse response, maximally flat FD FIR filter and Farrow structure. Compares are drawn among the methods. Result shows that the sampling rate, number of taps and number of quantification digitals will affect the performance of FD filters. The results are presented in detail. Also, the impact of using FD filter to realize wideband digital beamforming is analyzed and simulation shows that when the linear time delay bandwidth is designed properly, the performance of wideband digital beamforming and pulse compress are similar as ideal time delay.Finally, The impact of number of sub arrays and finite word length effect is discussed when FD filter is used to realize wideband digital beamforming. Simulation result shows the radar system cost is reduced when the number of sub arrays is designed reasonably, In the mean time good systematic performance can obtained. Also, the impact of quantization error is omitted when the number of quantification digitals is designed properly. Moreover, Two implementation methods of FD filter are presented.