Patent ID: 7340232
Filing Date: 2008-03-04
Classification: H04B

Abstract:
1. A semiconductor integrated circuit device for processing a wireless communication signal having therein a receiving circuit, comprising: a local oscillator for generating an oscillation signal of a desired frequency; a 90-degree phase-shifting circuit for generating a signal obtained by shifting a phase of the oscillation signal output from the local oscillator by 90 degrees; a first mixer for mixing one of differential reception signals with an output signal of said 90-degree phase-shifting circuit and outputting frequency-converted differential signals; a second mixer for mixing another one of said differential reception signals with an output of said local oscillator and outputting frequency-converted differential signals; an in-phase signal component averaging circuit having passive elements connected between the differential outputs of said first mixer, between differential outputs of said second mixer, and between an output of said first mixer and an output of said second mixer, and for reducing a DC offset created due to a difference between in-phase signal components included in output signals of said first and second mixers; a first differential amplifier for amplifying the output signal of said local oscillator; a second differential amplifier for amplifying the output signal of said 90-degree phase-shifting circuit; and a second in-phase signal component averaging circuit having passive elements connected between differential outputs of said first differential amplifier, between differential outputs of said second differential amplifier, and between an output of said first differential amplifier and an output of said second differential amplifier, and for reducing a DC offset created due to the difference between in-phase signal components included in output signals of said first and second mixers.