Injection locking phase rotator for Outphasing transmitter

This paper presents a novel technique of implementing the amplitude information into out-phase mapping, which is a necessary block of the high-efficiency Outphasing transmitter architecture. The proposed technique is based on using injection locking ring oscillator and switching-based control circuit to implement phase rotator. The technique is compatible with digital implementation using DSP. Since, Outphasing transmitters use switching power amplifiers, this implementation is suitable for an all-digital and adjustable transmitter implementation. The modulator system is designed using UMC130 nm CMOS technology; and is simulated at 1.8 GHz operation frequency, as it is commonly used in multiple mobile applications requiring high power levels. Simulation shows an out-phasing error of 0.41° rms, across the whole input amplitude sweep of 45 dB. The power consumption of the single phase rotator is 1.5 mW from 1.2 V supply.