Title:  Staggered Pattern Energy Harvesting and Retro-directive Backscatter Communications for Passive RFID Tags and Sensors

Committee:

Dr. Gregory Durgin, ECE, Chair , Advisor

Dr. Andrew Peterson, ECE

Dr. Paul Steffes, ECE

Dr. Manos Tentzeris, ECE

Dr. Hoseon Lee, KSU

Dr. Shawn Rogers, Honeywell

Abstract:

This work introduces an optimal backscatter and energy harvesting solution for radio frequency identification (RFID) by using N antennas with N ports called a staggered patterned and retro-directive (SPAR) tag. By using the same physical area as a lower frequency single antenna tag, SPAR tags improve both the power-up and backscatter range of passive RFID tags without dramatically impacting coverage. By using multiple ports on the SPAR tag, the structure is able to create multiple radiation patterns. This is demonstrated by using a two-element patch antenna array fed by a unitary scattering matrix (implemented as a 90˚ hybrid) on a 5.8 GHz RFID tag. In addition to canonical designs, new SPAR structures are hypothesized with optimized size, bandwidth, etc. A co-simulator is developed capable of searching a vast space of possible feed networks with N-by-N ports that meet the requirements of a unitary scattering matrix. A new structure that meets the 2-by-2 SPAR scattering matrix requirements is presented to demonstrate the capabilities of the software. The software can also be generalized to discover new physical structures of larger N−by−N SPAR tags or other microwave devices such as circulators, power splitters, etc.