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WWB13: Retrodirectivity

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In this lecture, we discuss the origins of retrodirectivity, starting with the Van Atta array and its use as radar chaff.  We then demonstrate how to use these systems in communications links.  Part of the Shenzhen lecture series on wireless without batteries.

WWB13: Retrodirectivity
Paper:  C.R. Valenta, B. Marshall, M.S. Trotter, G.A. Koo, G.D. Durgin “Staggered Pattern Charge Collection and Retrodirective Active Phase Modulation: Two New Passive Sensing Technologies.” IEEE RFID Conference, Orlando, FL. April 2012.

 

2008: Invention of the Griffin Modulator

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2008: Josh Griffin built a custom 5.8 GHz down-converter and demonstrated tag gains at 5.8 GHz when small, multiple tags are modulated jointly. Thus, Griffin modulation was born!

Josh Griffin demonstrates how the modulation of two antennas beside one another with identical signals significantly improves the backscatter data link (contrary to conventional radio links).  Not only does the extra antenna scatter more power (rather than simply re-arrange the gain pattern), but the additional scattered impart peculiar and improved fading behavior to a multipath channel.

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Invited Paper on Retrodirective Rat-Race Circuit Now Available on IEEExplore

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Theory and Design of a Retrodirective Rat-Race-Based RFID Tag
Mohammad Alhassoun, Michael A. Varner, Gregory D. Durgin
IEEE Journal of Radio Frequency Identification
Year: 2018

The full-length journal paper on Mohammad Alhassoun’s rat-race design for retro directive RFID tags is now available on IEEExplore.  The work presents a new design for a microwave antenna and feed topology that allows a single IC to control retro directive behavior and modulate information back to a reader.  This invited paper was an extension of the award-winning conference paper by Mr. Alhassoun.

Low-Powered Microwave Reader for Satellites

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Low-power and Compact Microwave RFID Reader for Sensing Applications in Space
Cheng Qi, Joshua D. Griffin, Gregory D. Durgin
IEEE International Conference on RFID Technology & Application (RFID-TA)
Macau SER, Sep 2018, 6 pages

Paper from the IEEE RFID-TA 2018 conference presenting the latest generation microwave backscatter reader developed by the lab.  Winner of the best student paper award.