Three-Level De-Multiplexed Dual-Branch Complex Delta-Sigma Transmitter

Area of Science:

• Electrical Engineering
• Signal Processing
• Wireless Communications

Background:

• Existing transmitter topologies face challenges in achieving high efficiency and linearity simultaneously.
• Delta-Sigma Modulators (DSMs) offer high resolution but often require complex digital-to-analog conversion.
• Switch-mode power amplifiers (SMPAs) provide high efficiency but can suffer from linearity issues.

Purpose of the Study:

• To propose and validate a novel dual-branch transmitter topology utilizing a Complex Delta-Sigma Modulator (CxDSM).
• To enhance transmitter efficiency and linearity, particularly improving Adjacent Channel Leakage Ratio (ACLR).
• To investigate the performance of a back-to-back SMPA design driven by de-multiplexed CxDSM signals.

Main Methods:

• A 3-level quantized signal from a CxDSM is de-multiplexed into two bi-level streams.
• Quantization Noise Reduction with In-band Filtering (QNRIF) is applied to each stream.
• De-multiplexed signals drive a dual-branch back-to-back SMPA amplification block with dynamic load modulation.
• The topology was implemented and tested using an LTE signal on the BEEcube™ platform.

Main Results:

• The dual-branch topology achieved over 72% coding efficiency across 1.8 GHz to 2.7 GHz.
• Significant improvements in linearity and ACLR were observed.
• The back-to-back SMPA design demonstrated efficient operation at peak power.

Conclusions:

• The proposed dual-branch CxDSM topology offers a highly efficient and linear transmitter solution.
• De-multiplexing and QNRIF techniques effectively mitigate quantization noise and improve spectral performance.
• This approach is suitable for modern wireless communication standards like LTE.