Patent ID: 6014571
Filing Date: 2000-01-11
Classification: H04B

Abstract:
A multiband mobile unit communication apparatus comprising:antenna means for receiving a plurality of radio wave signals respectively transmitted from a plurality of mobile unit communication systems, said plurality of radio wave signals having different carrier frequencies respectively;a plurality of independent circuits (101a, 101b) for generating a plurality of intermediate frequency signals from said plurality of radio wave signals from said antenna means respectively; anda common circuit (102) including receiving means (32, 106) for receiving one of said plurality of intermediate frequency signals in accordance with a mode signal, a quadrature demodulation circuit (15) for directly converting one of said plurality of intermediate frequency signals into I and Q baseband signals, and a decoding circuit (19) for outputting a decoding result from said I and Q baseband signals,wherein each of said plurality of independent circuits comprises:a first bandpass filter (3, 4) for bandpass-filtering each of said plurality of radio wave signals from said antenna means;an amplifier (5, 6) for amplifying an output of said first bandpass filter;filtering means (7, 8) for filtering an output of said amplifier;a mixer (9, 10) for mixing an output of said filtering means with a first local oscillation signal to generate an intermediate frequency signal;a second bandpass filter (11, 12) for bandpass-filtering said intermediate frequency signal and said common circuit further comprises:variable gain amplifying means (14, 14') for amplifying said one of plurality of intermediate frequency signal with a gain thereof controlled in accordance with a gain control signal and supplying the amplified intermediate frequency signal to said quadrature demodulation circuit,a first a/d converter (17) for a/d converting said I baseband signal and supplying the converted I baseband signal to said decoding circuit;a second a/d converter (18) for a/d converting said Q baseband signal and supplying the converted Q baseband signal to said decoding circuit;level detection means (20) for detecting levels of the converted I and Q baseband signals;gain control signal generation means (21) for generating said gain control signal in accordance with said detected level;a mode signal generation means (35) for generating said mode signal;a first local oscillation signal generator (13) for generating said first local oscillation signal; anda second local oscillation signal generator (16) for generating said second local oscillation signal.