Abstract
In this paper, a dual-branch topology driven by a Delta-Sigma Modulator (DSM) with a complex quantizer, also known as the Complex Delta Sigma Modulator (CxDSM), with a 3-level quantized output signal is proposed. By de-multiplexing the 3-level Delta-Sigma-quantized signal into two bi-level streams, an efficiency enhancement over the operational frequency range is achieved. The de-multiplexed signals drive a dual-branch amplification block composed of two switch-mode back-to-back power amplifiers working at peak power. A signal processing technique known as quantization noise reduction with In-band Filtering (QNRIF) is applied to each of the de-multiplexed streams to boost the overall performances; particularly the Adjacent Channel Leakage Ratio (ACLR). After amplification, the two branches are combined using a non-isolated combiner, preserving the efficiency of the transmitter. A comprehensive study on the operation of this topology and signal characteristics used to drive the dual-branch Switch-Mode Power Amplifiers (SMPAs) was established. Moreover, this work proposes a highly efficient design of the amplification block based on a back-to-back power topology performing a dynamic load modulation exploiting the non-overlapping properties of the de-multiplexed Complex DSM signal. For experimental validation, the proposed de-multiplexed 3-level Delta-Sigma topology was implemented on the BEEcube™ platform followed by the back-to-back Class-E switch-mode power amplification block. The full transceiver is assessed using a 4th-Generation mobile communications standard LTE (Long Term Evolution) standard 1.4 MHz signal with a peak to average power ratio (PAPR) of 8 dB. The dual-branch topology exhibited a good linearity and a coding efficiency of the transmitter chain higher than 72% across the band of frequency from 1.8 GHz to 2.7 GHz.
Highlights
The increasing demand of the new telecommunication standards in terms of bandwidth, spectral efficiency and power efficiency has led to the development of novel transceiver architectures and a continuous improvement in their performance
Previous works have focused on improving the performance of Delta-Sigma Modulator (DSM)-based transmitters in terms of Coding Efficiency (CE) and improvement of the DSM quantization noise shaping, mainly by Sensors 2018, 18, 626; doi:10.3390/s18020626
DSM quantization and de-multiplexes into two separate streams based on the magnitude of the DSM signal. This topology aims to improve the overall efficiency of the transmitter using an amplification block based on combined and non-isolated Switch-Mode Power Amplifiers (SMPAs) while preserving the signal quality
Summary
The increasing demand of the new telecommunication standards in terms of bandwidth, spectral efficiency and power efficiency has led to the development of novel transceiver architectures and a continuous improvement in their performance. For transmitters where the requirements of high power efficiency, wide coverage range and autonomy are stringent. This is in addition to the limitations of hardware processing resources, which prevent the implementation of complex linearization techniques. A topology based on Complex Delta-Sigma Modulation (CxDSM) is implemented, composed of a baseband signal-processing block, an up-conversion block and, an amplification block. DSM quantization and de-multiplexes into two separate streams based on the magnitude of the DSM signal This topology aims to improve the overall efficiency of the transmitter using an amplification block based on combined and non-isolated Switch-Mode Power Amplifiers (SMPAs) while preserving the signal quality.
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