Patent ID: 8494069

Claim:
A phase correcting apparatus for a radio transmitter, the phase correcting apparatus comprising: a demodulator which extracts a feedback signal from a part of a first baseband signal, and extracts a second baseband signal from the feedback signal by a first carrier wave signal; a modulator which modulates a difference signal between the first baseband signal and the second baseband signal by a second carrier wave signal and which outputs a second radio signal; a power amplifier which amplifies the second radio signal to obtain the first radio signal; a phase difference detector which detects a phase difference between the first baseband signal and the second baseband signal; and a phase rotator which rotates, by using the phase difference as a target phase correction amount, any phase of the first baseband signal, the second baseband signal, the first carrier wave signal, or the second carrier wave signal as a target phase correction amount, wherein the phase difference detector comprises a first analog processing circuit which obtains a first analog signal by multiplying an I component of the first baseband signal and a Q component of the second baseband signal, a second analog processing circuit which obtains a second analog signal by multiplying a Q component of the first baseband signal and an I component of the second baseband signal, and a digital processing circuit which converts a difference between the first analog signal and the second analog signal into digital data, and which detects the phase difference based on the converted digital data.