Sigma delta modulators with modified hybrid integrators

Abstract

This paper describes a modified second-order sigma-delta (SigmaDelta) modulator using hybrid integrators that is designed for WLAN applications. Hybrid integrators are composed of analog and digital integrators where the overflow of an analog integrator is processed by a digital integrator which results in the improvement of dynamic range. It is shown that the presented modulator achieves 8-dB improvement in dynamic range compared to conventional sigma delta modulator with the same oversampling ratio (OSR) and also it is very robust incase of any mismatch between the analog and the digital blocks. Another significant advantage of this scheme is that the overload level (OL) is increased by about 8.6-dB. The presented modulator architecture is implemented using a sampling frequency of 320 MHz for a 10 MHz signal bandwidth with an oversampling ratio of 16.