Theory and design of next-generation retrodirective tags and their channels
Abstract
Passive and semi-passive backscatter communication systems such as radio-frequency identification (RFID) experience several challenges that limit their proliferation especially at microwave and millimeter-wave (mm-wave) frequencies, a consequence from the round-trip and low-powered nature of these systems. These challenges manifest themselves in the forms of backscatter-communication range reduction, deep spatial nulls caused by the rapid change in the received power within a small area, or both. To overcome these challenges, a retrodirective-array-equipped backscatter transponder (an RFID tag) is used to replace the standard single-antenna transponder. The benefits of using retrodirective tags are twofold: First, since retrodirective tags that operate at microwave and mm-wave frequencies have similar propagation properties--in terms of power losses and field-of-view--to the current single-antenna RFID tags, which operate at ultra-high frequency (UHF) band, the higher-frequency retrodirective tags maintain the same coverage distance as the UHF tags and permit faster data rates by leveraging the spectrum availability at microwave and mm-wave regimes. Second, retrodirective tags reduce the randomness of the backscatter channel by changing the small-scale statistical behavior of the channel from double- to single-fading statistics, much like current one-way wireless channels--an original contribution of this research. This work presents a compact, novel, and high spectral-efficiency microwave structure using a ring-based retrodirective array. Furthermore, this research investigates, theorizes, and measures the small-scale statistical characteristics of retrodirective backscatter channels. In fact, a two order of magnitude reduction in the channel fade margin is measured when a retrodirective tag replaces its single-antenna counterpart--a significant improvement in the reliability of the backscatter link. The analyses, results, and designs in this research are key enablers for next-generation microwave and mm-wave, ubiquitous, and power-free RFID and Internet-of-things (IoT) systems.
Collections
Related items
Showing items related by title, author, creator and subject.
-
Covert communication: From classical channels to quantum channels
Tahmasbi, Mehrdad (Georgia Institute of Technology, 2020-04-24)The objective of this dissertation is to study covert communications over classical and quantum channels. In contrast to the well-studied notion of secrecy, in which one attempts to protect the content of information, ... -
Trellis coded, adaptive rate hybrid-ARQ protocols over AWGN channels and slowly fading rician channels
Rasmussen, Lars Kildehoj (Georgia Institute of Technology, 1993-08) -
A variable-channel queuing model with a limited number of channels
Phillips, Cecil Randolph (Georgia Institute of Technology, 1960-08)