Patent ID: 7936162

Claim:
A measured-signal repetition frequency detection method comprising: a first stage for detecting a frequency Fh of a specified signal appearing in a band not more than one half of a provisional sampling frequency Fs among signals obtained by sampling a measured signal with the provisional sampling frequency Fs; a second stage for calculating a frequency change amount ΔFh of the specified signal obtained with a sampling frequency changed from the provisional sampling frequency Fs by a minuscule frequency ΔFs not generating a frequency fold at a time of sampling; a third stage for calculating a sample number n from Equation (1): n=ΔFh/ΔFs (1) where a denominator is the minuscule frequency ΔFs in the second stage and a numerator is the frequency change amount ΔFh of the specified signal in the second stage; a fourth stage for calculating a provisional repetition frequency Fx′ of the measured signal based on the provisional sampling frequency Fs, the frequency Fh of the specified signal for the provisional sampling frequency Fs, the minuscule frequency ΔFs as a change amount of the sampling frequency and the frequency change amount ΔFh of the specified signal; a fifth stage for detecting a frequency change amount dFh_meas of the specified signal obtained in the case where the measured signal is sampled with a sampling frequency changed greatly from the provisional sampling frequency Fs so as to generate the frequency fold at a time of sampling and calculating an error en contained in the sample number n calculated in the third stage with a frequency fluctuation contained in the measured signal, based on a detected frequency change amount dFh_meas of the specified signal and a change amount dn of the sample number n calculated in the third stage indicating how many times the frequency fold has occurred in this process; and a sixth stage for calculating a regular repetition frequency Fx of the measured signal by correcting the provisional repetition frequency Fx′ of the measured signal calculated in the fourth stage based on the error en contained in the sample number n calculated in the fifth stage.