Research And Design Of Millimeter-wave Frequency Synthesizer

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 frequency synthesizer is the key module that have heavily influence on the quality of transmitting signal and 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 8mm frenquency synthesizer which have low-spurious and high resolution. 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 whole design includes DDS module,frequency multiplier module,PLL I&II module,mixer module,control circite module.The mm-wave signal is generated through three up-converters and the LFM signal is got byDDS. 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 500Mhz and minimum frequency step is 10MHz , the spur level of the transmitte signal is less than -60dBc respectively, the phase noise level is all less than -85dBc/Hz@1kHz.,the maximum frequency converting time is less than 10μs.At last, the frequency synthesizer meet the system's requirements.