Patent ID: 7912148

Claim:
A transmission circuit for generating and outputting a transmission signal based on input data, the transmission circuit comprising: a signal generation section for generating an amplitude signal and an angle-modulated signal in accordance with an amplitude component and a phase component which are obtained by performing signal processing on the input data; an amplitude modulation section for amplitude-modulating the angle-modulated signal and outputting a resultant signal as a modulation signal; a temperature measuring section for measuring a temperature of the amplitude modulation section; a memory for prestoring offset reference values which are to be references for calculating an offset compensation value, the offset reference values being a temperature of the amplitude modulation section measured at an initial state of the amplitude modulation section, an offset compensation value of the amplitude modulation section calculated when the amplitude modulation section is at the initial state, and a rate of change of offset compensation value with respect to a relative change in temperature of the amplitude modulation section; an offset compensation section for compensating for a magnitude of the amplitude signal by (i) calculating an amount of difference between the temperature of the amplitude modulation section at the initial state and a temperature of the amplitude modulation section at a current state measured by the temperature measuring section as the relative change in temperature, (ii) calculating the offset compensation value for compensating for an offset characteristic of the amplitude modulation section using the relative change in temperature, the rate of change of offset compensation value, and the offset compensation value of the amplitude modulation section at the initial state, and (iii) adding the calculated offset compensation value to the amplitude signal; and an amplitude amplifying section for receiving the amplitude signal from the offset compensation section and outputting a signal corresponding to the magnitude of the amplitude signal, wherein the amplitude modulation section amplitude-modulates the angle-modulated signal by using the signal output from the amplitude amplifying section and outputs the resultant signal as the modulation signal.