| 摘要 |
PROBLEM TO BE SOLVED: To improve reception performance even when the flatness of a frequency characteristic in an IF band is spoiled owing to variance among tuner components. SOLUTION: The IF signal from a tuner 51 is divided into three frequency bands by SAW filters 1 to 3 having mutually different center frequencies. The output level of an IF AGC amplifier 4 is determined by making gain adjustment according to the signal level of a lower frequency band from the SAQ filter 1, a comparator 10 compares the DC voltage generated by detecting and smoothing its output by a smoothing and detecting circuit 7 with the DC voltage generated by detecting and smoothing the output from the AGC amplifier 5 by a smoothing circuit 8, and the gain of the IF AGC amplifier 5 is so adjusted that the difference between the both is eliminated. Further, a comparator 11 compares the DC voltages generated by the smoothing and detecting circuits 7 and 9 and the gain of an IF AGC amplifier 6 is adjusted. Consequently, the flatness of the frequency characteristic is improved to decrease the disorder and gradient of the frequency characteristic within the correctable range of an equalizer of a demodulator 14. COPYRIGHT: (C)2003,JPO
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