Study On The Modeling And Simulation Of A Sigma-Delta Modulator Used In WLAN

As the improvement of wireless communication, its standards are always upgraded. Thisbrings the higher and higher requirements to relative hardwares and equipments. Comparedwith the conventional ADC, the sigma-delta ADC is insensitive to analog circuitimperfections and component mismatch, more suitable for integration and can achieve a veryhigh resolution for the use of oversampling and noise shaping technique. Therefore, it hasbeen widely used in many fields. However, limited by sampling frequency, sigma-delta ADChas a narrow bandwidth and a slow rate, which makes it can’t adapt to the higher and higherspeed of wireless communication. So the research of a wideband sigma-delta ADC is veryimportant.In this paper, a wideband2-1-1-1low-distortion MASH(Multi-Stage noise shaping)sigma-delta modulator is presented for WLAN(Wireless Local Area Network) application,whose both first stage and last stage employ a4-bit quantizer. At first, we give out the indexof performance, analyze the principle of sigma-delta modulator and discuss the twoarchitectures of it. Then, it presents the complete design procedure of the modulator system.How to choice the architecture, determine the coefficients of it and get the Noise CancellationLogic are also descripted in detail in this section. The last section describes different kinds ofnon-idealities. We model and simulate them in matlab/simulink environment and get theirimpacts on system SNR. Then the required range of these module parameters is achieved. Thesimulation results of modulator with all non-idealities show a SNR of79.6dB and ENOB of12.93. This implies that the presented sigma-delta modulator can completely satisfy the needsof application in WLAN.