N-path Passive Mixers: Simple Circuits, Surprising Capabilities, Prof. Alyosha Molnar, 03/25/2022

Abstract: In this presentation I will discuss N-phase passive mixers (and their close relative the 'N-path filter') as applied to interference tolerant radio receivers. Although known for decades, the advent of deep-submicron CMOS has enabled N-path passive mixers and filters to be scaled to GHz frequencies with surprisingly good performance in both noise and, especially, linearity. I will briefly review the basic operation and properties of such circuits, and provide an intuitive analysis of the circuit and transistor properties that limit their performance, including insights into their response to phase noise. Such N-path mixers, as originally conceived, and as implemented in the sub-10GHz regime, however, place requirements on their Local Oscillator waveforms that are ill-suited to the higher frequency (e.g. mm-wave) operation required for newer standards such as 5G. I will therefore also introduce a second set of design techniques and analytical results enable similar function at much higher frequencies. Speaker biography: Alyosha Molnar received his B.S. in engineering from Swarthmore College in 1997, and M.S. (2003) and Ph.D. (2007) in electrical engineering from the University of California, Berkeley. From 1998 to 2002, he was with the RFIC Group at Conexant Systems, Inc., Newport Beach, CA, where he co-led the development of their first-generation GSM direct conversion receiver. In graduate school he worked on one of the first sub-milliwatt radios for 'smart dust', before spending several years in a neuroscience lab studying the biological circuits that underlie early image processing in the mammalian retina. In 2007, he became a faculty member with the School of Electrical and Computer Engineering at Cornell University. His research interests span RF and mm-wave integrated circuits for flexible wireless systems, novel image sensors and associated image processing, neuroscience and neural interface systems and circuits, and microscale autonomous systems. He is a recipient of many teaching and research awards including the NSF CAREER award, DARPA Young Faculty Award, and the ISSCC Lewis Winner award.