| 摘要 |
The frequency measurement method and associated apparatus accurately determines the frequency of a periodic signal even if the frequency exceeds the nyquist frequency, typically established by the analog to digital ("A/D") converter used to sample the signal. The frequency measurement method and apparatus obtains samples of a periodic signal at a number of sample rates, converts the samples to the frequency domain, analyzes the first order alias frequencies produced due to undersampling of the signal, and determines the frequency of the periodic signal based upon the alias frequencies. In selecting the sampling rate and the first order alias frequencies, the frequency measurement method and apparatus accounts for sampling errors, frequency calculation errors, desired frequency ranges, and measurement precision. Through error compensation and minimization techniques, the frequency measurement method and apparatus reduces the number of electrical components required (e.g. A/D converters). Further, the error compensation and minimization techniques utilized by the frequency measurement method and apparatus allows the use of shorter transforms for converting the time-domain data to the frequency domain, which thereby increases calculation speed while estimating the frequency of the periodic signals with greater accuracy.
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