Georgia Tech ECE Research Group
A lecture from the Wireless Without Batteries Series on thermoelectric devices. The principles of thermoelectric devices and their use in energy-harvesting.
WWB06: Thermoelectric Devices
Paper: D. Nemir and J. Beck, “On the Significance of the Thermoelectric Figure of Merit Z,”Journal of Electronic Materials, vol. 39, no. 9, pp. 1897–1901, 2010.
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 multiple ports and a unitary scattering matrix on the SPAR tag, the structure is able to create multiple orthogonal radiation patterns to improve range of passive RFID tags. This is demonstrated on a 5.8 GHz RFID tag using a two-element patch antenna array fed by a 90˚ hybrid. 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.
This lecture in the Wireless Without Batteries Series discusses the fundamentals of Power Optimized Waveforms (POWs), which can be used to extend the range of wireless energy-harvesting links.
WWB05: Power-Optimized Waveforms
Paper: M.S. Trotter, J.D. Griffin, and G.D. Durgin. “Power-Optimized Waveforms for Improving the Range and Reliability of RFID Systems.”IEEE International Conference on RFID 09, Orlando, FL. April 2009. 8 pages.
Michael Varner’s publication at IEEE SPAWC 2018 is now available for download in IEEExplore. Entitled “Reflection of Modulated Radio (ReMoRa): Link Analysis of Ambient Scatter Radio Using Perfect Pulses“, the work explores the spectral properties for perfect pulse modulation of ambient backscatter. The impact on this modulation scheme and the link budget is explored. The ideas in this paper will allow long-range communications by embedding information on existing RF sources and reflecting them to collection nodes. There are numerous applications in machine-to-machine, internet-of-things, and sensor networks.