{"id":5757,"date":"2012-07-18T22:27:43","date_gmt":"2012-07-18T22:27:43","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2012\/?p=5757"},"modified":"2012-07-18T22:32:18","modified_gmt":"2012-07-18T22:32:18","slug":"continuous-time-delta-sigma-analog-to-digital-converters-for-application-to-multiple-input-multiple-output-systems","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2012\/continuous-time-delta-sigma-analog-to-digital-converters-for-application-to-multiple-input-multiple-output-systems\/","title":{"rendered":"Continuous-time Delta-sigma Analog-to-digital Converters for Application to Multiple-input Multiple-output Systems"},"content":{"rendered":"

As wireless communication technology is rapidly advancing, new wireless applications are continuously developed. Figure 1 shows each application space and the required dynamic range [1<\/a>] <\/sup>. The new wireless applications demand wideband (50-MHz) and high resolution data converters (>14 bits). Delta-sigma (\u0394\u03a3) analog-to-digital converters (ADCs) are best suited for their ability to achieve high resolution. However, the large bandwidth required poses a significant challenge.\u00a0 \u0394\u03a3 ADCs can be implemented in either a discrete-time (DT) or a continuous-time (CT) structure. Since DT\u00a0 \u0394\u03a3 ADCs require op amp settling within each half clock period, the gain-bandwidth requirement for the op amp is extremely high for the sampling rate required for 50MHz bandwidth. The CT\u00a0 \u0394\u03a3 ADCs require much lower gain-bandwidth. Thus, CT DS ADCs can function at a higher sampling frequency and achieve a wider bandwidth compared to DT\u00a0 \u0394\u03a3 ADCs. In addition, since the CT\u00a0 \u0394\u03a3 ADCs are more power-efficient and have an inherent anti-aliasing property, they are more suitable for the demanding new wireless applications<\/p>\n

This project focuses on the design of CT\u00a0 \u0394\u03a3 ADCs, specifically for the application in multiple-input multiple-output wireless receivers. For this application, each CT\u00a0 \u0394\u03a3 ADC in a channel must provide wide bandwidth and high dynamic range at low power consumption. The state-of-art CT\u00a0 \u0394\u03a3 ADCs do not come close to achievingwide enough bandwidth and high enough dynamic range for such applications [2<\/a>] <\/sup> [3<\/a>] <\/sup>. We are investigating a new type of a CT multi-stage noise-shaping (MASH)\u00a0 \u0394\u03a3 ADC based on a DT sturdy-MASH \u0394\u03a3 ADC [4<\/a>] <\/sup>. Figure 2 shows the overall structure of a CT MASH \u0394\u03a3 ADC. The main advantage of this new type of CT \u0394\u03a3 ADCs is that it does not require digital filters that conventional MASH \u0394\u03a3 ADCs need to cancel out the quantization error of the first stage. We have developed several new techniques to make a CT MASH \u0394\u03a3 ADC faster, more accurate, and robust.<\/p>\n\n\t\t