High-frequency modulated-backscatter communication using multiple antennas

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dc.contributor.author Griffin, Joshua David en_US
dc.date.accessioned 2009-06-08T18:43:17Z
dc.date.available 2009-06-08T18:43:17Z
dc.date.issued 2009-03-02 en_US
dc.identifier.uri http://hdl.handle.net/1853/28087
dc.description.abstract Backscatter radio - the broad class of systems that communicate using scattered electromagnetic waves - is the driving technology behind many compelling applications such as radio frequency identification (RFID) tags and passive sensors. These systems can be used in many ways including article tracking, position location, passive temperature sensors, passive data storage, and in many other systems which require information exchange between an interrogator and a small, low-cost transponder with little-to-no transponder power consumption. Although backscatter radio is maturing, such systems have limited communication range and reliability caused, in part, by multipath fading. The research presented in this dissertation investigates how multipath fading can be reduced using multiple antennas at the interrogator transmitter, interrogator receiver, and on the transponder, or RF tag. First, two link budgets for backscatter radio are presented and fading effects demonstrated through a realistic, 915 MHz, RFID-portal example. Each term in the link budget is explained and used to illuminate the propagation and high-frequency effects that influence RF tag operation. Second, analytic envelope distributions for the M x L x N, dyadic backscatter channel - the general channel in which a backscatter system with M transmitter, L RF tag, and N receiver antennas operates - are derived. The distributions show that multipath fading can be reduced using multiple-antenna RF tags and by using separate transmitter and receiver antenna arrays at the interrogator. These results are verified by fading measurements of the M x L x N, dyadic backscatter channel at 5.8 GHz - the center of the 5725-5850 MHz unlicensed industrial, scientific, and medical (ISM) frequency band that offers reduced antenna size, increased antenna gain, and, in some cases, reduced object attachment losses compared to the commonly used 902-928 MHz ISM band. Measurements were taken with a custom backscatter testbed and details of its design are provided. In the end, this dissertation presents both theory and measurements that demonstrate multipath fading reductions for backscatter-radio systems that use multiple antennas. en_US
dc.publisher Georgia Institute of Technology en_US
dc.subject Backscatter radio en_US
dc.subject Radio frequency identification en_US
dc.subject RFID en_US
dc.subject Fading channels en_US
dc.subject Probability en_US
dc.subject Multipath channels en_US
dc.subject Rayleigh channels en_US
dc.subject Microwave propagation en_US
dc.subject Backpropagation en_US
dc.subject Microwave radio propagation en_US
dc.subject.lcsh Antennas (Electronics)
dc.subject.lcsh Backscattering
dc.subject.lcsh Radio frequency identification systems
dc.title High-frequency modulated-backscatter communication using multiple antennas en_US
dc.type Dissertation en_US
dc.description.degree Ph.D. en_US
dc.contributor.department Electrical and Computer Engineering en_US
dc.description.advisor Committee Chair: Durgin, Gregory; Committee Member: Ingram, Mary Ann; Committee Member: Nikitin, Pavel; Committee Member: Peterson, Andrew; Committee Member: Steffes, Paul en_US

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