| 摘要 |
A first band-pass filter extracts, from a first sound intermediate frequency signal, a signal having a frequency in the vicinity of a center frequency of the first sound intermediate frequency signal. Then, a mixer down converts a signal extracted by the first band-pass filter to a second sound intermediate frequency signal. A low-pass filter extracts, from the second sound intermediate frequency signal, a signal having a frequency in the vicinity of a center frequency of the second sound intermediate frequency signal or a lower frequency. With such an arrangement, FM detection can be performed preferably even if the frequency of the first sound intermediate frequency signal is deviated. |
