| 摘要 |
A phase reversal detector converts an input tone from time domain into frequency domain, determines a phase difference over a time interval, and detects a phase reversal, based on the phase difference. The converter derives a Fourier transform coefficient having a centre frequency corresponding approximately to a principal frequency being sought in the incoming signal. It uses a very short window of samples, the window length being selected to be shorter than that required for an exact correspondence. By using an approximate correspondence a much shorter window can be used, which enables a significant reduction in computational load and a shorter detection time. The converter output is a complex number. The phase difference is obtained using a dot product of the outputs of the converter obtained at different times. An average of consecutive phase differences can be used to reduce the effect of noise. |
