| 摘要 |
An apparatus having a complex sine wave generating circuit (3) that generates a complex sine wave, a multiplying circuit (4) that multiplies an input signal by the complex sine wave, a first integrating circuit (5) that integrates the product obtained by the multiplying circuit (4) in the time direction, a first squaring circuit (6) that takes the square of the absolute value of a complex signal output by the first integrating circuit (5), a second squaring circuit (7) that takes the square of the absolute value of the instantaneous amplitude of the input signal, a second integrating circuit (8) that integrates the results obtained by the second squaring circuit (7) in the time direction, and a frequency difference calculating circuit (9) that finds the difference between the frequency of the input signal and the oscillation frequency of the complex sine wave on the basis of the ratio between the output signal level of the first squaring circuit (6) and the output signal level of the second integrating circuit (8). A frequency difference detection apparatus can be obtained that can detect the difference between the frequency of the input signal and a given reference frequency even when the input signal includes much noise.
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