Patent ID: 7555281

Claim:
A RF receiving apparatus comprising an input terminal; a direct conversion system mixing circuit supplied at one input with RF signal inputted to the input terminal while at another input with an oscillation signal of local oscillator, for outputting a plurality of output signals whose phases are different to each other; a suppression part supplied with the output of the mixing circuit; an output terminal supplied with the output of suppression part; a detector for detecting DC offset voltage contained in the output signals of the mixing circuit; a control section interposed between the output of the detector and the input of the suppression part, wherein the control section outputting a signal to the suppression part for suppressing the DC offset voltage when the detector detected the DC offset voltage; a level comparator supplied with the oscillation signal for comparing an oscillation signal level with a certain predetermined threshold value; and a driving section interposed between the output of level comparator and the control section, when the level comparator detects that the signal level exceeded the threshold value, the level comparator signals the driving section to trigger the control section to control the suppression part to suppress the DC offset voltage.