短波段频率合成器的设计与调试

Design and Debugging of Short Wave Frequency Synthesizer

设计了基于锁相环的短波段正弦信号合成器,其工作原理为原始的正弦波输出信号由压控振荡器产生,经芯片分频输出一个低频方波信号,参考信号采用Q值较高的晶体产生,然后输出到芯片的分频,在芯片内部输出一个低频方波信号,两路低频方波信号同时由芯片内部的数字鉴相器进行比相,输出一个反映相位误差值的双路差分电压信号到有源环路低通滤波器,经它滤波形成近似直流的信号,控制压控振荡器的变容管反相偏置电压来调整振荡频率。仿真结果达到预期要求。

A short wave sine signal synthesizer based on PLL was designed,in which the sine wave output signal was generated by voltage-controlled oscillator,the frequency of which was divided by a prescalar,and further divided by in-chip counter,resulting in a square-wave signal with low frequency inside the chip;the reference signal was generated by a high Q crystal oscillator,the frequency of which was divided by a counter inside the chip;the 2 channels of low frequency square-wave signal were applied into the digital phase detector,a dual-way differential signal reflecting phase error was output to an active low-pass active filter,an approximate DC signal was generated to control the inversely-biased voltage on the varactor to control the VCO frequency.The simulation results show that the design can meet the requirement of actual project.