| 摘要 |
PROBLEM TO BE SOLVED: To prevent distortion of an RF signal and deterioration of receiving performance when receiving a CATV broadcasting signal or a terrestrial wave TV broadcasting signal. SOLUTION: A tuner unit 1 includes: an RF signal input terminal 2 which inputs the RF signal of multiple channels; an AGC circuit 4 which is arranged in a succeeding stage of the RF signal input terminal 2, and fixes or controls the gain by a first gain control signal; a wide band amplification circuit 5 arranged in a succeeding stage of the AGC circuit 4; an AGC circuit 6 which is arranged in a succeeding stage of the wide band amplification circuit 5, and fixes or controls the gain by a second gain control signal; a mixer circuit 7 which selects and takes out a signal of a desired channel from an output signal of the AGC circuit 6; an AGC switching circuit 15 which controls the AGC circuit 4 and the AGC circuit 6 by selecting whether the gain of the AGC circuit 4 is fixed or controlled, and at the same time, selecting whether the gain of the AGC circuit 6 is fixed or controlled. COPYRIGHT: (C)2009,JPO&INPIT
|
