基于CORDIC算法的正交信号源实现

Implementation of quadrature signal source based on CORDIC algorithm

正交型数字锁相放大器中正交信号参考源对于数字锁相放大器的性能有着重要的影响,根据CORDIC算法在FPGA上设计数字正交信号源,实现了直接数字频率合成(DDS)技术中的相位/幅度转换模块,可输出高精度的正交参考信号,避免了用ROM实现相幅转换时硬件开销过大及处理速度受限制的问题。首先介绍了DDS的工作原理,同时对基于CORDIC算法的相幅变换方法进行了详细叙述,利用CORDIC算法计算正余弦值,最后对整体模块进行了仿真和实验测试,输出中心频率可调的正交信号,实现了高精度的正交信号源。

The quadrature signal reference source has the significant impact on the performance of the quadrature digital lock-in amplifier. According to CORDIC algorithm,the digital quadrature signal source was designed on FPGA. The phase/amplitude transformation module in DDS technology was realized,which can output the high precision quadrature reference signal,and solve the problems of large hardware cost and limited processing speed when ROM is used to realize phase/amplitude transformation. The DSS working principle is introduced. The phase/amplitude transformation method based on CORDIC algorithm is described in detail,in which the CORDIC algorithm is used to calculate the sine and cosine values. The simulation and experimental test for the entire module are conducted,it can output the quadrature signal with adjustable center frequency. The high precision quadrature signal source is realized.