Radio receiver and intermediate frequency signal generation method

A radio receiver comprising:

• a first oscillator whose oscillation frequency is variable;
• a quadrature demodulator including a frequency mixer mixing a radio frequency signal and an oscillation signal outputted from the first oscillator and generating an intermediate frequency signal having an intermediate frequency lower than the frequency of the radio frequency signal;
• a band pass filter band-limiting the intermediate frequency signal by the passing characteristic selected from a plurality of passing characteristics;
• a filter control unit controlling the passing characteristic of the band pass filter;
• a filter information storage unit storing passing characteristic information including information representing the center frequency of the passband of each of the passing characteristics;
• a frequency control unit controlling the oscillation frequency so that the frequency of the intermediate frequency signal is a predetermined frequency;
• and
• a frequency correction unit referring to the passing characteristic information and correcting the oscillation frequency controlled by the frequency control unit,
• wherein in a state where the filter control unit controls the passing characteristic of the band pass filter to a first passing characteristic, the frequency control unit controls the oscillation frequency so that the frequency of the intermediate frequency signal is the predetermined frequency,
• wherein after the frequency control unit controls the oscillation frequency so that the frequency of the intermediate frequency signal is the predetermined frequency, the filter control unit controls the passing characteristic of the band pass filter from the first passing characteristic to a second passing characteristic having a passband width narrower than the passband width of the first passing characteristic, and
• wherein when the passing characteristic of the band pass filter is changed from the first passing characteristic to the second passing characteristic, the frequency correction unit refers to the filter information storage unit, and corrects the oscillation frequency controlled by the frequency control unit by the amount according to the difference between the center frequency of the first passing characteristic and the center frequency of the second passing characteristic.