Patent ID: 6208875
Filing Date: 2001-03-27
Classification: H03L,H04B

Abstract:
An RF dual band phone circuit operating in the DCS 1800 and GSM frequency bands, comprising:a modulator for producing an output comprising a pair of baseband signals (I and Q) modulating a first intermediate frequency (IF) signal for the GSM band or a second intermediate frequency (IF) signal for the DCS 1800 band;a receive phase lock loop for generating a high side injection local oscillator signal for the GSM band and a low side injection local oscillator signal for the DCS 1800 band;a transmit phase lock loop for translating the first IF signal to a GSM band radio frequency signal or the second IF signal to a DCS 1800 band radio frequency signal, depending on which one of the two local oscillator signals is supplied to it, the GSM band signal or the DCS 1800 band signal being down converted and fed back to the IF input of the transmit phase lock loop; andan amplifier for amplifying the output of the transmit phase lock loop and for supplying the amplified signal to an antenna.