Correction for phase drift in an AM-PM distortion calibration system for an envelope tracking RF amplifier

摘要

The RF signals at the input and output of an envelope-tracking power amplifier 102 are sampled and coupled to receivers in the processor 208 in order to determine the instantaneous gain and phase performance of the amplifier when subject to a test signal 224. The test waveform (figure 3c) contains periods in which the test signal is representative of a realistic transmission signal alternating with reference periods when the test signal has a constant amplitude. Phase measurements made during the reference periods allow correction of phase drift caused by local oscillator phase noise in the measuring system. A shaping function applied to the envelope signal 222 may be varied.