| 摘要 |
A transmitter has a power amplifier ( 40 ) to amplify an input signal having amplitude modulation, a supply voltage controller ( 10 ) to control a supply voltage of the power amplifier ( 40 ) according to the envelope, a sensor (R 1 ) for sensing a modulation of a current drawn by the power amplifier ( 40 ), a delay detector ( 20 ) for detecting a delay of the controlled supply voltage relative to the sensed current, and a delay adjuster ( 30 ) for compensating the relative delay according to the detected delay. By sensing a current drawn, the delay detected can include any delay contributed by the power amplifier ( 40 ) up to that point, and yet avoid the more complex circuitry needed to derive the delay from an output of the power amplifier. Thus the distortion and out of band emissions caused by differential delays can be reduced more effectively.
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