Patent ID: 7454186

Claim:
A direct conversion receiving apparatus, comprising: a gain control amplifier for input a base band signal and a gain switching control signal to control a gain, and variably amplify the base band signal based on the gain switching control signal; a high pass filter having an input terminal for input the output signal of said gain control amplifier, an output terminal, a first circuit including plural capacitors connected in parallel that are inserted in a path connecting the input terminal to the output terminal and switching effective total capacitance of the plural capacitors based on a first time constant switching control signal, and a second circuit including a resistor for providing a predetermined direct current voltage to the output terminal and switching the effective resistance value of the resistor based on a second time constant switching control signal; and a control circuit for output the gain switching control signal, and the first and second time constant switching control signals to control the cutoff frequency of said high pass filter according to the change of the gain control of said gain control amplifier, wherein, during the normal operation, said control circuit sets the capacitance values of the first circuit at a first capacitance value based on the first time constant switching control signal, and sets a resistance value of the second circuit at a first resistance value based on the second time constant switching control signal; and on switching the gain of said gain control amplifier, said control circuit switches the capacitance values of the first circuit to a second capacitance value that is smaller than the first capacitance value at a third timing after a second timing at which the gain of said gain control amplifier is switched, and returns the resistance value of the second circuit to the first resistance value at a fourth timing after the third timing.