Direct conversion receiving apparatus and celluar phone

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
• the first circuit includes a first capacitor connecting the input terminal to the output terminal, and a serial circuit connected to the first capacitor in parallel and made of a second capacitor and a first time constant switching circuit connected to the second capacitor in series, said first time constant switching circuit being turned on/off on the basis of the first time constant switching control signal and connecting the second capacitor to the first capacitor in parallel when turned on;
• and
• the second circuit includes a first resistor providing a predetermined direct current voltage to the output terminal, and a second time constant switching circuit connected to the first resistor in parallel, said second time constant switching circuit being turned on/off on the basis of the second time constant switching control signal and causing a short-circuit in the first resistor when turned on.

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
• the first circuit includes a first capacitor connecting the input terminal to the output terminal, a serial circuit connected to the first capacitor in parallel and made of a second capacitor and a second resistance, and a first time constant switching circuit connected to the second resistor in parallel, said first time constant switching circuit being turned on/off on the basis of the first time constant switching control signal and causing a short circuit in the second resistor when turned on;
• and
• the second circuit includes a first resistor providing a predetermined direct current voltage to the output terminal and a second time constant switching circuit connected to the first resistor in parallel, said second time constant switching circuit being turned on/off on the basis of the second time constant switching control signal and causing a short circuit in the first resistor when turned on.