An Asynchronous Sigma Delta Analog to Digital Converter for Broadband Wireless Receiver with Adaptive Digital Filtering Technique

Abstract

This paper focuses on the circuit design techniques for an asynchronous sigma delta Analog to Digital Converter (ADC). The key advantage of this ADC approach is the potential for dynamic range to improve with the evolution of CMOS fabrication process. In contrast, conventional synchronous sigma delta ADC does not enjoy the benefit of improved dynamic range and lower power consumption from the scaling of CMOS fabrication process. The asynchronous approach has already been proposed in the past, but no actual circuits have been designed and published. As a case study, the asynchronous sigma delta ADC is designed according to Worldwide Interoperability for Microwave Access (WiMAX) communication standard. Novel circuit elements, such as integrator, hysteresis comparator and the time to digital converter (TDC), are proposed in this paper for the asynchronous sigma delta ADC. The overall power consumption of this ADC is just 9.4 mW, which is one of the lowest compared to the existing synchronous sigma delta designs.