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Retrodirective MIMO Communications

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Partitioned Pseudo-retrodirective Arrays for Capacity Expansion of Backscatter Communication Channels

Michael A. Varner; Mohammad Alhassoun; Gregory D. Durgin
2018 IEEE International Conference on RFID, Orlando, FL, April 2018

In this paper, we outline the benefits of subdividing a retrodirective array into segments and using MIMO-style (multiple-input, multiple-output) signaling to reflect multiple streams of independent data back to a reader.  The rules for making this happen are different than a conventional MIMO link.

Retro-Reflective RFID Tags

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Design and Evaluation of a Multi-modulation Retrodirective RFID Tag

Mohammad Alhassoun; Michael A. Varner; Gregory D. Durgin
2018 IEEE International Conference on RFID, Orlando, FL, April 2018

This paper is Mohammad Alhassoun’s award-winning idea for an RFID tag exhibits retrodirectivity. Unlike previous designs, this scheme can be implemented by a single chip that alternately load-modulates two inner ports of a rat-race hybrid.  Previous retrodirective designs have all required switches and electronics at multiple locations to reconfigure the structure, which greatly increases the cost of production.

UW Invited Talk on Low-Powered Microwave Backscatter — 2010!

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The University of Washington EE Department hosts the Lytle Lecture series, dating back quite a ways.  In addition to the recent lecture by Prof. Durgin, this series has — over the last decade — hosted numerous talks about how low-powered communications and energy-harvesting technology have changed over the years.  Here is an example by a visiting Associate Professor in 2010.  (Thanks to my friend, Prof. Denise Wilson, for the invitation.)

https://www.youtube.com/watch?v=H4DACyB_iqo

 

Spread Spectrum Backscatter

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RFID Anti-Collision System Using the Spread Spectrum Technique

Anil Rohatgi, PG-TR-050426-AR, 26 April 2005

This is a classic undergraduate research study involving the use of spread spectrum signaling in backscatter links.  Aside the novelty and quality of Rohatgi’s work, this was the work that Dan Deavours spotted a few year later.  He then invited our group to give a talk on the subject at IEEE RFID 2008 in Las Vegas  — a move that led to a fruitful, decade-long partnership that continues today.