Design of a band-pass sigma-delta modulator with reduced number of opamps

Abstract

This paper is intended to compare the performance of a Band-Pass converter structure and its Low-Pass prototype 2nd order Sigma-Delta Analog to Digital converter. For this purpose Matlab simulations for the 4th order Band-Pass converter have been performed and its power consumption calculated when using the equivalent Op-Amp used m the Low-Pass modulator. First of all will be described the method used to calculate the transfer function and, thus the structure of the Band-Pass structure to be tested. After a band-pass transfer function has been obtained it is implemented using reduced number of opamps. This topology is compared to the existing ones and a system level simulation and characterisation is performed. Finally, jitter limitations are studied. Transistor level simulations using Spectre have been done in order to validate MATLAB simulations prior to layout design.