Patent ID: 7260373

Claim:
A direct conversion receiver, comprising: a pair of mixers which convert a receive signal frequency to a baseband frequency; a baseband frequency signal processing block including a pair of first gain control amplifiers and a pair of first filters, following said mixers; and a pair of DC offset cancellation circuits, each comprising: an analog to digital converter which is connected to an output of one of said pair of first gain control amplifiers to convert analog signals to digital signals; a digital processing circuit which detects a DC offset voltage out of output signals from said analog to digital converter and calculates a voltage to cancel the DC offset voltage; and a digital to analog converter which converts a digital signal of the voltage calculated by the digital processing circuit into an analog signal of the voltage and supplies the analog signal of the voltage to said one of said pair of first gain control amplifiers, wherein said baseband frequency signal processing block further includes a pair of negative feedback circuits with an adjustable feedback factor, each negative feedback circuit including a second filter of low-pass type, wherein said direct conversion receiver performs DC offset cancellation by means of said pair of DC offset cancellation circuits when being powered on and, subsequently, performs DC offset cancellation by means of said pair of negative feedback circuits.