Graduation Semester and Year

2007

Language

English

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering

Department

Electrical Engineering

First Advisor

Daniel Engels

Abstract

In this paper we collect and extend the theory of radio frequency (RF) propagation as it relates to propagation within metal cylinders, or circular pipes. This work is motivated by a need to understand the operation of UHF radio frequency identification (RFID) systems when the tags are placed within the pipes. These circular pipes are shown to be similar to metal tube waveguides which are either hollow or filled with air. We derive the Bessel function that is used to identify the propagation constants, the different transverse electric and transverse magnetic modes, cut-off frequencies and the multi-mode attenuation. The cut-off frequencies, angle of incidence and attenuation are used within the theory to identify operating limitations of passive RFID systems in hollow metal pipes. Source excitations are used to discuss the characteristics of multi-modal RF propagation. A comprehensive general theory is developed to enumerate the workings of passive RFID systems in circular metal pipes. Analytical evaluations are used to visualize the tags within the metal pipes and to validate the theory presented in this paper. It is shown that passive UHF RFID tags can be read even below the cutoff frequencies of these circular metal pipes when used under the guidance of the general theory. It is also shown that a helical or modified helical tag antenna design would yield high readability rates when impedance matched appropriately to the application specific integrated circuit (ASIC) in the RFID tag.

Disciplines

Electrical and Computer Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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