FPGA Based Implementation of All-phase FFT Phase Difference Frequency Measurement

The principle of the phase difference spectrum corrector is to extract spectrum information from the phase difference of two subsequences before and after delay. This study aims to achieve real-time and high-precision frequency measurement of discrete sinusoidal signals. This article proposes a frequency measurement algorithm based on all-phase FFT and frequency shift. And this new algorithm is easy to implement on FPGA. In addition to extracting the phase difference information of the original sequence, the new algorithm also extracts the phase difference information of the frequency shift sequence. When calculating the frequency, only the phase difference information of the branch with a minor frequency offset from the discrete spectral line is selected. Benefit from the smaller frequency offset, the new algorithm has better anti-noise ability. An experiment on the Altera DE2-115 FPGA board shows that when the input signal is the sinusoidal signal with a 10-bit width and a sampling rate of 100MSPS, the frequency measurement result is output in double-precision floating-point within 10 microseconds, and the frequency measurement error is within 1Hz.