Patent ID: 8045650

Claim:
A radio receiving apparatus for frequency-converting a radio frequency signal into an intermediate frequency signal and demodulating the radio frequency signal, the radio receiving apparatus comprising: a frequency conversion section for converting the radio frequency signal into first and second intermediate frequency signals, based on two local oscillation signals in phases 90 degrees different from each other; a first analog-to-digital conversion section for converting the first intermediate frequency signal into a first digital signal; a second analog-to-digital conversion section for converting the second intermediate frequency signal into a second digital signal; a demodulation section for making corrections to amplitudes and phases of the first and second digital signals and for rejecting image frequency signals from the first and second digital signals, so as to convert the obtained signals into signals of a baseband bandwidth; and a correction value calculation section for obtaining, by calculations, an amplitude correction value and a phase correction value which are used for making corrections to the amplitudes and the phases of the first and second digital signals in the demodulation section, wherein the correction value calculation section combines a first signal, which is obtained by multiplying the first digital signal by an amplitude correction candidate value and rotating the phase of the first digital signal, with a second signal, which is obtained by multiplying the second digital signal by a multiplicative inverse of the amplitude correction candidate value and performing, for the second digital signal, phase rotation which is in a quadrature relationship to phase rotation performed for the first digital signal, so as to obtain a first combined signal, and wherein the correction value calculation section includes a determination section that (i) obtains an inflection point of the first combined signal, and (ii) inputs, to the demodulation section, the amplitude correction candidate value and the phase correction candidate value, which correspond to the inflection point, as the amplitude correction value and the phase correction value, respectively.