RF carrier phase-burst transmitter

The potential high efficiency of RF carrier-burst transmitters has drawn the increasing attention of various researchers. This architecture uses an on-off mode of a constant-amplitude phase modulated carrier, according to the selected envelope-to-duty-cycle conversion (PWM or sigma-delta), requiring an implementation with two transistors, often in class-D configuration. This paper proposes a significant modification to this traditional architecture, where now the phase modulated carrier is always on - and thus allowing a single transistor implementation - but where the amplitude is impressed into the carrier phase according to a bi-phase code. A proof-of-concept prototype tested with a CDMA2000 signal achieved 59% of average efficiency and more than 34dBc of ACPR for an integrated output power of 24.7 dBm.