Architectural techniques for envelope and phase signal alignment in rf polar transmitters using power amplifier feedback

Abstract

In an envelope comparison embodiment, a delay calibrator produces a delay signal based on a comparison of a feedback signal and an envelope component of the transmitted signal. A down-converter produces the feedback signal from an outgoing modulated RF signal based on at least one local oscillation. Envelope detectors in the delay calibrator and the envelope signal path are operably coupled to a summing node that produces a delay error signal based on a temporal difference between the two envelopes. One embodiment includes phase detectors to detect and adjust the zero crossings of the feedback signal and the envelope signal path. As the delay mismatch between the envelope signal path and the phase signal path increases, the power spectrum increases in adjacent communication channels. A mask margin measurement technique measures the power level in an adjacent channel and adjusts the envelope path delay accordingly.