A ΔΣ-Digitized RF Transmitter

This paper demonstrates a new transmitter architecture digitizing an envelope to control a power amplifier. The transmitter employs a low-pass ΔΣ-modulator for constant envelope modulation and noise shaping. It enables the use of highly efficient switching amplifier with high linearity. For demonstration, the overall transmitter is implemented and tested with code-division multiple access (CDMA) IS-95A signal. The transmitter delivered the expected efficiency and linearity. The performances are maintained across the broad output power range. The results clearly show the controllability of highly efficient switching power amplifier in digital domain with simple envelope modulation technique.