| 摘要 |
A quadrature modulator multiplies two carriers which are 90.degree. out of phase with each other by a sine component and a cosine component of a baseband signal, respectively, adds the product signals to each other, and amplifies the sum signal to produce a quadrature-modulated output signal. The quadrature modulator includes a phase comparator for detecting a phase distortion suffered when the sum signal is amplified, a first phase controller for correcting the phase of a single carrier generated by a carrier oscillator based on a compared phase output signal from the phase comparator, a phase difference detector for detecting the difference between 90.degree. and the phase difference between the two carriers, and a second phase controller for outputting the two carriers to be multiplied by the sine and cosine components of the baseband signal and controlling the phase difference between the two carriers generated from the single carrier whose phase distortion has been corrected by the first phase controller, into 90.degree. based on a detected output signal from the phase difference detector.
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