Patent ID: 7224948

Claim:
A transmitter comprising a first frequency synthesizer; a second frequency synthesizer; a base band circuit for outputting a base band signal and a control signal on the basis of an information signal; a control circuit for changing output frequencies of the first frequency synthesizer and the second frequency synthesizer on the basis of the control signal; a modulator for assuming an output signal from the first frequency synthesizer to be a carrier signal and modulating the carrier signal on the basis of the base band signal; and a frequency conversion circuit for using an output signal from the modulator and an output signal from the second frequency synthesizer to upconvert a carrier frequency of the output signal from the modulator, wherein the frequency conversion circuit comprises a first phase comparator; a first low pass filter; a first VCO; and a mixer, and the frequency conversion circuit is a PLL frequency conversion circuit in which the first phase comparator outputs a signal proportional to a phase difference between an output signal from the modulator and an output signal from the mixer; the first low pass filter is connected to an output of the first phase comparator; the first VCO is connected to an output of the first low pass filter; the mixer is adopted to mix an output signal from the first VCO and an output signal from the second frequency synthesizer.