Patent ID: 7013090

Claim:
A transmitting circuit apparatus comprising: a frequency modulator that performs frequency modulation of a carrier wave with frequency modulation data and outputs the frequency-modulated carrier wave; a sigma-delta modulator which performs sigma delta modulation of amplitude modulation data; and an amplitude modulator that performs amplitude modulation of the frequency-modulated carrier wave with an output signal of the sigma-delta modulator and outputs the amplitude-modulated carrier wave; wherein the frequency modulator has a phase-locked oscillator, which includes at least a variable frequency divider, and a second sigma-delta modulator, wherein the second sigma-delta modulator outputs a value, which is obtained by performing second-order or higher-order sigma-delta modulation of data which is obtained by adding the frequency modulation data to carrier frequency data, as a division number of the variable frequency divider, and wherein the frequency-modulated carrier wave is outputted from the phase-locked oscillator.