Patent ID: 8040158

Claim:
A frequency difference detection apparatus for detecting a difference between a frequency of an input signal and a predetermined reference frequency, the frequency difference detection apparatus comprising: a complex sine wave generating means for generating a complex sine wave having an oscillation frequency equal to the reference frequency; a multiplication means for multiplying the complex sine wave generated by the complex sine wave generating means by said input signal; a first integrating means for integrating a result of multiplication by the multiplication means in the time direction; a first absolute value calculating means for finding a value proportional to an absolute value, or a square of the absolute value, of a result of integration by the first integrating means; a second absolute value calculating means for finding a value proportional to an absolute value, or a square of the absolute value, of an instantaneous amplitude of said input signal; a second integrating means for integrating a result obtained by the second absolute value calculating means in the time direction; and a frequency difference calculating means for finding the difference between the frequency of said input signal and the reference frequency, based on a ratio between a result obtained by the first absolute value calculating means and the result obtained by the second integrating means.