一种基于改进平方环的MSK解调方法的FPGA实现

摘要

The design of MSK demodulation system is an important part of automatic data link test technology and the carrier synchronization plays a major role in it.The MSK characteristics are analysed and a carrier synchronization method using modified squaring loop is studied.It uses modified CORDIC algorithm in NCO to reduce occupation of hardware resources.Based on the orthogonal property of NCO output sine and cosine waves,a method of direct coherent carrier extraction without frequency-halving circuit is proposed.This modified squaring loop is more simple for hardware implementation and the feasibility is proved by ModelSim simulation.%二进制最小频移键控(MSK)解调系统的设计是数据链自动测试技术中的重要部分,而载波同步在MSK解调中起到了关键性作用.从分析MSK信号特性出发,研究了一种采用改进平方环的载波同步方法,在传统平方环的基础上,将改进坐标旋转数字(CORDIC)算法应用到数控振荡器(NCO)中,极大减少了对硬件资源的占用,利用NCO产生两路完全正交的正、余弦信号的特点,提出一种直接提取相干载波的方法,免除了复杂的二分频电路.这种改进平方环在硬件实现上更为简单,通过Modelsim软件进行仿真,验证了这种改进平方环的可行性.