| 摘要 |
PROBLEM TO BE SOLVED: To reduce an IC manufacture cost in the case of constituting the reception part of AM/FM bands by one chip as an integrated circuit by rationalizing a noise detection circuit. SOLUTION: Upon receiving the broadcasting station signals of the AM band, first and second switches 31 and 32 are switched, an intermediate frequency amplifier / amplitude limiting circuit 27 is connected to a second band filter 16 and an FM detector 28 is connected to a gate signal generation circuit 33. The circuit of the reception part of the FM band detects pulse noise superimposed on AM modulation signals upon receiving the broadcasting station signals of the AM band. When the AM modulation signals converted to intermediate frequency signals in the reception part of the FM band are input to the intermediate frequency amplifier / amplitude limiting circuit 27, the signals of fixed frequency and amplitude are output, a frequency and a phase are shifted at the superimposed part of the pulse noise. The shift is detected in the FM detector having the same carrier frequency as the intermediate frequency signals of the reception part of the AM band. Noise is detected by using a part of the reception part of the FM band, and a noise component detection part is rationalized without newly adding a circuit. COPYRIGHT: (C)2006,JPO&NCIPI
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