| 摘要 |
An automatic frequency control apparatus for an FM receiver. The apparatus includes a local oscillator for generating a local oscillation signal which frequency is controlled in response to a received input FM signal, a frequency converter for convertig the input FM signal into an IF signal having a center frequency in response to the local oscillation signal from the local oscillator, an FM demodulater for demodulating the IF signal into a demodulated output having AC and DC components, a low pass filter for removing the AC component from the demodulated output, a first A/D converter for converting the remaining DC component of the demodulated output to a digital tuning signal, a reference voltage source for supplying a reference voltage corresponding to the center frequency of the IF signal, a second A/D converter for converting the reference voltage from the referrence voltage source to a digital reference voltage signal, and a microcomputer for calculating the demodulation sensibility of the digital tuning signal from the digital tuning signal and the digital reference voltage signal and for generating an AFT data signal in response to the demodulation sensibility of the digital tuning signal for controlling the frequency of the local oscillation signal.
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