Inherently Linear Multi-Cell Digital Sigma Delta Modulator Using Mixed-Coupling Mode

Authors

  • Yogita Gajare, Arti Khaparde

Abstract

this paper presents the power efficient design and implementation of single bit multi-cell digital sigma delta modulator for wireless transmitters. Wastage of bandwidth can incredibly be lessened by low over sampling ratio. Hence, higher order sigma delta modulator is highly preferred custom chip in high frequency applications. Splitting of modulator structure into a number of stages is possible to avoid stability problem of higher order of the modulator.  In the conventional splitting type algorithm, multibit quantizer achieves de-correlation between quantization noise signals in the coupling through delay. But multibit quantizer has the problem of linearity. This paper highlights inherently linear split type modulator based on the dual single bit quantizers with mixed-coupling. Proposed structure includes self-coupling acts as an error feedback and dither input simultaneously in a local position. Therefore, overall error is shaped by third order. However, previous stage quantization noise is injected in the next stage through coefficient instead of delay to achieve de-correlation between quantization noise signals for higher order. This cross-coupled noise acts as a dither to randomize   in band noise. Further, this paper focuses on the power optimization of proposed structure to fix the order and over sampling ratio with single bit quantizer under the requirement of wireless standards. Figure of Merit is calculated to confirm power consumption. Circuits are simulated in MATLAB SIMULINK to carry out the performance analysis. Functional verification is validated through Vivado tool using Digilent Basys3 Artix-7 board.

Keywords- Sigma Delta Modulator; Over Sampling Ratio; Coupling; Quantizer; Order; Power

Published

2020-11-30

Issue

Section

Articles