Apple Inc.
Calibration techniques for envelope tracking power amplifiers

Abstract:

There is provided a technique for calibrating the envelope tracking circuitry of the wireless interface of an electronic device to compensate for any delay mismatch between the IQ signal path and the envelope path. The desired levels of input test signals are determined to assure that they are sensitive to any delay mismatch which may be in the system. The propagation delay from the signal generator to the signal analyzer of the envelope tracking system is estimated and delay compensation is performed. To reduce the noise of the measurement, distortion in the received signal may also be determined and noise compensation may also be performed. Based on these determinations, the envelope tracking circuitry may be calibrated by introducing an appropriate delay in either the envelope path or the IQ signal path.