.8 Mm Full Coherent Radar Transceiver Front-end Development

Due to the millimeter wave's characteristics of short wavelength,wideband and so on, it has been applied comprehensively in track and guidance radar,electronic countermeasure,millimeter wave communication. As is known to us, the mm-wave system's T/R front end is the key module that have heavily influence on the quality of transmitting signal and receiver's noise figure,sensitivity and output SNR. As for the automatic tracking radar, it uses LFM(Linear Frequency-Modulated) signal with adjustable pulse width as the transmitting signal to take account of radar range and range discrimination,reduce system power consumption and extract target information effectively. Now, the common technology of the LFM signal's generation is Direct Digital Frequency Synthesis(DDS),but it can only generate LFM signal in low frequency band, the mm-wave LFM signal's generation must depend on the very important module - frequency synthesizer which must have higher and higher performance on frequency band,frequency step,spectral purity and converting time in the modern electronic system.This dissertation presents the designing of T/R front end of coherent radar in 8mm band. By good frequency programming, circuits designing and the using of DDS, PLL, FPGA chips, the frequency synthesizer not just be implemented more easier but also has good performance of spectrum purity and converting time during the deigning of the T/R frond end. The mm-wave LFM signal is generated through three up-converters and the IF signal of receiver is got by two down-converters. The converters'local oscillators is implemented by the frequency multiplier and PLL. The testing displays that , in S/C band , the local oscillator's bandwidth is 480Mhz and minimum frequency step is 15MHz , the spur level of receiver's local oscillator and transmitter is less than -70dBc and -65dBc respectively, the phase noise level is all less than -94dBc/Hz@1KHz.,the maximum frequency converting time is less than 15us.At last, the frequency synthesizer meet the frond end's requirements.