Coding Efficiency Enhancement Using Time Interleaved Level Splitting and Optimized Multi-Level Delta Sigma Modulation in Digital Transmitter

Abstract

This paper proposes a novel scheme for energy-efficient transmitter design using optimized multi-level DSM (OML-DSM) along with time-interleaved level splitting technique. This scheme significantly improves the overall transmitter efficiency by providing high coding efficiency (CE) at the DSM stage and high drain efficiency (DE) at the amplification stage. The position of quantization level and quantization level selection window range is optimized in OML-DSM to achieve better CE compared to conventional multi-level DSM. These optimized multi-level signals are further split into bi-level signal streams using time-interleaved level splitting technique to improve the DE at the amplification stage. A 10 MHz LTE signal with 12 dB PAPR is used for simulation and measurement purposes. For hardware validation, 6-level OML-DSM is applied, which converts the 10 MHz LTE signal into six quantization levels and level splitter split these multi-levels into three bi-level signal streams with different magnitude and power levels. These bi-level signal streams are amplified using class-E SMPAs. The output of SMPAs is combined with Gysel unequal power combiner. Hardware results show that the CE and channel efficiency is improved by 18.7%, and 11.4%, respectively, compared to conventional 6-level DSM. The measured EVM is 2.2%, which shows good in-band performance.