Radio communications apparatus

摘要

A phase comparator ( 106 ) compares a phase of the output signal of the quadrature modulator ( 104 ) with the phase of the signal obtained by frequency-converting the output signal of a first VCO ( 101 ) via the second VCO ( 102 ) and the first mixer ( 108 ). A PLL modulator includes a low-pass filter ( 107 ) filters a component below a predetermined frequency of the output signal of the phase comparator ( 106 ) and supplying the resulting signal to the frequency control terminal of the first VCO ( 101 ). The output signal (TS 1 ) of the first VCO ( 101 ) is a modulated signal conforming to a modulation system having a constant envelope waveform, while the output signal of the quadrature modulator ( 104 ) is input to the first band-pass filter ( 110 ) and the output signal (TS 2 ) of the first band-pass filter is a modulated signal conforming to a modulation system accompanied by an amplitude component as information.