A CMOS advanced class-S transmitter architecture based on tri-level envelope encoding

Abstract

An advanced class-S transmitter architecture using a tri-level envelope encoding is presented. With tri-level encoding based on a delta-sigma modulator (DSM), a coding efficiency is improved compared to the two-level case, and sampling frequency is lowered to 522.24 MHz, which leads to an enhanced system efficiency. An analog/RF interface block is designed to control the propagation delay of the envelope signal. A wideband mixer and drive amplifier are also included to combine the modulated envelope with the phase signal and shift the spectrum to a 2.6-GHz center frequency. Measurement results from an implementation in a 130 nm CMOS process show that the DSM achieves a peak signal-to-noise and distortion ratio of 44.4 dB in a 20-MHz input bandwidth. Transmitter measurements on a 10-MHz long-term evolution signal show an error vector magnitude of 3.2% and an adjacent channel leakage ratio of 40.5 dB at 2.6 GHz.