Systematic design of stable high-order delta sigma modulators using genetic algorithm

Abstract

Instability is a design challenge with high-order delta-sigma modulator (DSM). DSM stability shows maximum stable amplitude (MSA) where it achieves adequate precision across the bandwidth. Increasing DSM order reduces the stable amplitude range. In addition, the design of an efficient noise transfer function (NTF) is necessary for the synthesis of a DSM. In this brief, a systematic method to design stable high-order DSM without the need for a stability-recovery mechanism is presented. The proposed design method can be used for high-order single-bit and multi-bit DSM with maximum stability. To achieve maximum DSM amplitude stability, systematic simulation is used to design coefficients and obtain SNR values at different points of bandwidth. Actual SNR values will ensure that the genetic algorithm will search and find optimum stability coefficients, the most important feature of the proposed method. The design method is implemented for two DSMs with different specifications and the results are compared with similar studies, showing that the proposed method has acceptable performance.