Patent ID: 8155235

Claim:
A modulation apparatus that modulates a radio frequency signal subjected to on-off-keying modulation or quadrature phase shift keying modulation, the modulation apparatus comprising: a signal generating section that generates an I signal and a Q signal according to a modulation scheme; a first baseband processing section that performs baseband processing of the I signal, and generates a first baseband signal; a second baseband processing section that performs baseband processing of the Q signal, and generates a second baseband signal; a local oscillator that generates a carrier wave; a phase shifter that shifts a phase of the carrier wave; a first mixer that generates a first mixed signal by multiplying the carrier wave generated in the local oscillator and the first baseband signal; a second mixer that generates a second mixed signal by multiplying the carrier wave having the phase shifted in the phase shifter and the second baseband signal; a combining section that generates a radio frequency signal by adding the first mixed signal and the second mixed signal; and a phase control section that estimates a phase offset between an actual phase difference of carrier waves of the first and second mixed signals and a target phase difference of the carrier waves of the first and second mixed signals, and controls an amount of shift in the phase shifter to eliminate the phase offset, wherein the modulation apparatus further comprises a variable delay section that delays the first baseband signal or the second baseband signal, wherein the phase control section further estimates a transmission path difference between a transmission path of the first baseband signal and a transmission path of the second baseband signal based on the radio frequency signal, and controls an amount of delay in the variable delay section to eliminate the transmission path difference.