Design and analysis of a low-power constant envelope phase shift modulator

Commonly used constant envelope modulation schemes for wireless communications, such as GMSK and MSK, usually take on complex architectures in IC implementations. This paper describes a constant envelope phase shift modulator based on the OQPSK and MSK modulation schemes, and discusses some circuit design issues and their impact on the performance of the modulator. The modulator produces a signal with discrete step phase shifts, has a relatively simple architecture, consumes low power, and is designed to be integrated with a nonlinear power amplifier in a direct conversion transmitter.