Patent ID: 6914943

Claim:
A modulation circuit for obtaining a modulated signal, by modulating a carrier signal using a modulating signal, comprising: means for extracting a phase signal and an amplitude signal from the modulating signal; means for converting the phase signal into an analog signal; first means for generating a first oscillation frequency signal; means for modulating, using quadrature modulation, the analog signal output from the converting means to an IF signal, based on the first oscillation frequency signal; second means for generating a second oscillation frequency signal, means for converting the frequency of the IF signal output from the modulating means and converting the IF signal into a RF signal, based on the second oscillation frequency signal; means for delaying the amplitude signal output from the extracting means for a time; and means for varying the amplitude of the RF signal and amplifying the varied RF signal in accordance with the delayed amplitude signal output from the delaying means, and for outputting the amplified RF signal, wherein the delay means comprises: means for setting the time; and a delay circuit for delaying the amplitude signal output from the extracting means in accordance with the time set by setting means, the setting means including a circuit for setting the time, based on at least one of a modulation type, a modulation index, a frequency, a roll off rate of the modulating signal, an ambient temperature, a supply voltage to the modulation circuit, and a gain.