PHASE-LOCKED LOOP METHODS AND STRUCTURES FOR GENERATING MODULATED COMMUNICATION SIGNALS WITH NONCONSTANT ENVELOPES

摘要

Phase-locked loop methods and structures are provided for generating modulated communication signals with nonconstant envelopes. These methods and structures realize the improved communication performance of nonconstant-envelope modulation with the upconversion advantages of phase-locked loops. The structures include transmitters (100) in which a phase-locked loop (22) is augmented with first and second feedforward paths (45, 46) that substantially resotre phase and amplitude information to a transmit signal that is generated by a voltage-controlled oscillator (28) of the phase-locked loop. The first feedforward path is configured to realize a path transfer function of s/Kv wherein the voltage-controlled oscillator has a transfer function of Kv/s. The second feedforward path extracts an envelope-correction signal from the modulated intermediate-frequency signal and a variable-gain output amplifier (26) amplifies the transmit signal with a gain that responds to the envelope-correction signal.