| 摘要 |
PROBLEM TO BE SOLVED: To provide a receiver IF circuit which reduces costs of a receiver and a receiver substrate area by low-cost and high-performance integration of an image rejection filter and a channel selection filter. SOLUTION: A receiver IF circuit includes: a variable gain amplifier 2 for amplifying an RF input signal; a frequency converter 3a, 3b for obtaining, from the RF signal amplified by the variable gain amplifier polyphase intermediate-frequency signals that are used for suppressing an image component; a polyphase filter 5 for receiving the polyphase intermediate-frequency signals and outputting an intermediate-frequency signal whose image component is suppressed; a frequency variable band-pass filter 6 for selecting a channel of the intermediate-frequency signal outputted from a polyphase filter while changing a frequency response in accordance with a supplied control signal; an IF detector 8 for detecting the intermediate-frequency signal; and an automatic gain controller 9 for detecting a level of an output signal of the IF detector and controlling a gain of the variable gain amplifier in accordance with the detected level. COPYRIGHT: (C)2006,JPO&NCIPI
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