基于FPGA的全相位FFT高精度频率测量

High-precision frequency detection with APFFT based on FPGA

基于常规FFT时移相位差测频方法由于频谱泄漏的影响使得测频精度不高,且抗噪性能不好。采用具有初相不变特性的APFFT(全相位快速傅里叶变换)算法,结合实际工程应用要求,设计、仿真并在FPGA平台上实现了一种高精度的时移相位差频率测量方案。在MATLAB环境下的功能模拟和性能仿真,以及最终在FPGA平台实际检测的结果表明,该方案能有效克服频率泄漏对相位差测量的影响,测频精度高,抗噪性能强,并且具有测频绝对精度在大倍频程的测量频段内基本保持不变的优点(实例,绝对精度优于1Hz@1kHz～3600kHz),具有很高的工程应用价值。

The accuracy and the noise resistance of phase error method of frequency measurement based on conventional FFT is not ideal due to the leakage of frequency spectrum.This paper utilizes the phase invariant characteristics of all- phase FFT algorithm and under the engineering requirements realizes a high precision frequency measurement method on the FPGA platform.Simulation on MATLAB environment and FPGA platform both confirm that this method can effectively overcome the impact of frequency leakage and achieve high precision as well as good noise resistance. Especially,the absolute accuracy in large measure octave band remain unchanged（for example,absolute accuracy better than 1Hz@1kHz～3 600kHz）,which proves that this method has high value in engineering.