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 UMC130nm CMOS technology; and is simulated at 1.8GHz operation frequency, as it is commonly used in multiple mobile applications requiring high power levels. Simulation shows an out-phasing error of 0.41rms, across the whole input amplitude sweep of 45dB. The power consumption of the single phase rotator is 1.5mW from 1.2V supply.
phase rotator injection locking ring oscillator out-phasing transmitter phase modulation amplitude to phase modulation