一种高精度直接数字频率合成方法

摘要

利用卫星导航（Global Navigation Satellite System,GNSS）模块输出的秒脉冲信号,快速修正现场可编程逻辑阵列（Field Programable Gate Array,FPGA）芯片内部实现的直接数字频率合成（Direct Digital System,DDS）逻辑模块的频率控制字,并采用倒π型电阻网络对DDS模块输出的数字频率进行数模转换（Digital/anolog,D/A）转换,产生最终的高精度模拟频率。实测数据表明这种方法产生的频率不受晶振漂移的影响,能够达到较高的频率准确度,并且利用FPGA的灵活性,可以同时产生多路频率信号,应用方便、成本低廉。%This paper describes a high precision digital frequency synthesis manner,using the 1PPS signal of GNSS module to quickly amend the control word of DDS logic module which realized in FPGA chips,then transferring digital signal to analog signal by reverse π type resistor network.The experiment data shows that this method can generate a high precision frequency regardless of the excursion of crystal oscillator,furthermore using FPGA can generate multiplex frequency flexibly and cheaply.