Sharp Kabushiki Kaisha Corporation

Haruo Koizumi

Syuuji Matsuura

Mitsuhiro Noboru

Miyoshi Yamauchi

Toshifumi Akiyama

A demodulator controls gains of an RF-AGC amplifier and an IF-AGC amplifier so as to maintain an input level to the demodulator constant. In this case, the demodulator estimates a signal level of an RF input based on the sum of the gains directed to the both AGC amplifiers, and changes methods for distributing a gain to the AGC amplifiers, according to whether or not the signal level exceeds a predetermined Take Over Point. Further, a first detection and smoothing circuit detects an output level of the RF-AGC amplifier, and a second detection and smoothing circuit detects an output of a mixer. Besides, a comparison circuit controls the gain of the RF-AGC amplifier so that a difference between the output levels comes to be a predetermined value. With this structure, an automatic gain control circuit which can achieve high receiving sensitivity and low waveform distortion simultaneously can be realized even when manufacturing dispersion is caused.

Automatic gain control method and automatic gain control circuit

The tuner structure of the present invention includes: a circuit board on which electronic circuit components such as transistors and resistors have been mounted; a chassis angle; and a shield cover. In the tuner structure, a feedthrough capacitor for inputting/outputting a power, a control signal and the like is mounted to a metal plate disposed in parallel to the circuit board.

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Sennan, Japan

Haruo Koizumi