TRANSMITTER, TRANSMISSION/RECEPTION CIRCUIT, AND RADIO TRANSMISSION/RECEPTION SYSTEM

摘要

A transmitter comprises: a phase synchronization circuit that receives, from a first path, a first phase modulation signal for modulating a signal having a first frequency and that also receives, from a second path, a second phase modulation signal for modulating a signal having a second frequency higher than the first frequency; and a power amplifier that receives, from a third path, a third modulation signal for controlling the gain thereof. The phase synchronization circuit comprises: a variable frequency divider the frequency division ratio of which is controlled by the first phase modulation signal; a frequency modulation D/A converter that performs a frequency modulation D/A conversion of the second phase modulation signal; and a voltage-controlled oscillator that includes a varactor and that receives a first control voltage based on the first phase modulation signal, also receives a second control voltage based on the second phase modulation signal and controls the oscillation frequency. The phase synchronization circuit changes, on the basis of a data transfer rate, at least one of the capacitance value of the varactor in the voltage-controlled oscillator, the number of control bits of the frequency modulation D/A converter, and the bias current of the frequency modulation D/A converter.