Comparative Study between Duty Cycle Modulation (DCM) and Sigma-Delta (Ʃ∆) Modulation Based on Analog to Digital Conversion

Abstract

This paper presents a virtual comparative study between the Analog to Digital Conversion (ADC) based Duty Cycle Modulation (DCM) and Sigma-Delta (Ʃ∆) modulation. Indeed, the Ʃ∆ modulation is the most used oversampling technique to carry out analog to digital conversion up to now. Despite of its good performances, its hardware and software implementation remains rather complex and makes its development cost rather high. To overcome this weaknesses, the new oversampling technique, duty cycle modulation, makes it possible to have better performances with very simple hardware and software structure. Thus a first order Ʃ∆ modulator is compared with a duty cycle modulator at the same central frequency of modulation in virtual simulation in terms of analog circuit, demodulation technique and the dynamic characteristics of the converters. The simulation is carried out under Matlab/Simulink R2020a with modulators at the maximum frequency of 250KHz.The dynamic performances of converters under an analog modulating signal of 1KHz reveal a) for DCM technique: SNR=45.77dB, THD=0.05055% and ENOB=7.24 bits; b) for Ʃ∆ technique: SNR=38.86dB, THD=1.574% and ENOB=6.16 bits. These results present best performances of DCM technique compared to the Ʃ∆ technique in the simulation of analog to digital conversion.

Keywords

• duty cycle modulation
• sigma-delta modulation
• analog to digital conversion