Speaker: Prof. Nagendra Krishnapura, Department of Electrical Engineering, Indian Institute of Technology Madras (IIT Madras)
Title: Multi-channel Analog-to-Digital Conversion Using a Delta-Sigma Modulator Without Reset and a Modulated-Sinc-Sum Filter
Date & Time: October 24, 2:00 pm – 3:00 pm
Location: CEPSR 414
Host: Harish Krishnaswamy
Abstract: A new method is presented for converting any continuously running discrete-time delta-sigma modulator (DTDSM) into a multi-channel ADC by adding only a digital filter at the output. The inputs are multiplexed and fed to the ADC directly. The crosstalk that would exist if the decimation filter output is demultiplexed directly is canceled using the proposed modulated-sinc-sum digital filter. The modulated-sinc sum filter adjusts the weights of the replicas of the input spectrum in a way that, after downsampling, the aliases of crosstalk signals sum to zero. Compared to resetting the DSM and converting it to an incremental DSM, the proposed technique is at least 1.57 \times more power-efficient. A prototype two-channel ADC clocked at 6.144 MHz with a channel bandwidth of 22 kHz demonstrates the proposed technique. Fabricated in a 180 nm CMOS process, the prototype chip consumes 1 mW/channel, including the digital filters, and achieves a peak SNR of 94.4 dB and has a dynamic range of 98.5 dB. The inter-channel crosstalk is restricted to less than -93 dBc across the entire bandwidth and across temperature.
Speaker Bio: Nagendra Krishnapura obtained his BTech from the Indian Institute of Technology Madras and his PhD from Columbia University, New York. He has worked as an analog design engineer at Celight Inc., Multilink, and Vitesse semiconductor in the USA. He has taught analog circuit design courses at Columbia University as an adjunct faculty. Since 2005 he has been a faculty member at the Indian Institute of Technology Madras where he is currently a Professor. His interests are analog and RF circuit design, analog signal processing, and circuits and systems pedagogy. He has been an associate editor of the IEEE Transactions on Circuits and Systems 1 and 2, and been on the technical programme committees of the International Solid-State Circuits Conference and the Custom Integrated Circuits Conference. He is a fellow of the Indian National Academy of Engineering.