Passive Mixer Transparency and Its Implications for Software Defined Radio Receivers

Date: November 9, 2012
Time: 1:00pm-3:00pm
Speaker: Prof. Alyosha Molnar, Cornell University
Location: 633 Mudd
Hosted by: Columbia Integrated Systems Laboratory


Software defined radios (SDR) aim to make every critical parameter of a radio's function adjustable and configurable through digital control, without significantly degrading performance. In this talk I will discuss a recently (re)discovered approach to achieving such flexibility, by exploiting the transparency properties of multi-phase CMOS passive mixers. Such mixers, combined with appropriate baseband circuitry, can be used to synthesize arbitrary in-band impedance and filtering properties and up-convert them to their RF port. Such mixers also display unusually high out-of band linearity and surprisingly low in-band noise, making them an intriguing option for SDR receivers. I will discuss some of the fundamental theory and associated limits of such receivers, as well as enhancements to this architecture, and other applications of the mixer transparency.


Alyosha Molnar received his BS from Swarthmore College in 1997, and after spending a season as a deck-hand on a commercial Tuna fishing boat, worked for Conexant Systems for 3 years as an RFIC design engineer. He was co-responsible engineer developing their first-generation direct-conversion receiver for the GSM cellular standard. That chip, and subsequent variants, have sold in excess of 100 million parts. Starting graduate school at U.C. Berkeley in 2001, Molnar worked on an early, ultra-low-power radio transceiver for wireless sensor networks, and then joined a retinal neurophysiology group where he worked on dissecting the structure and function of neural circuits in the mammalian retina. He joined the Faculty at Cornell University in 2007, and presently works on low-power software-defined radios, neural interface circuits, and new integrated imaging techniques. He is recipient of the DARPA Young Faculty Award in 2010, NSF CAREER Award in 2012, and ISSCC Lewis Winner Award in 2012.

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