A Simple Adaptive Sigma Delta Modulators for Software Defined Radio

In this paper we propose a simple and flexible design of analog-to-digital converter based on a single adaptable architecture of high order single loop sigma delta modulator suitable for multimode operation and adaptive wireless systems. The modulator is adaptable to operate in different signal bandwidth and signal-to-noise ratio (SNR) by varying the feedback gain values of local resonators and integrators that optimize the noise transfer function of the loop filter while also meeting the stability constraint. A capacitor array implementation is employed to generate the desirable range of gain values. It is shown by simulation that it meets the SNR and bandwidth requirements of different wireless standards such as GSM and WCDMA and provides a simple reconfigurable platform.