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Analysis and design of ferroelectric-based smart antenna structures
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Paper Abstract

Ferroelectrics in microwave antenna systems offer benefits of electronic tunability, compact size and light weight, speed of operation, high power-handling, low dc power consumption, and potential for low loss and cost. Ferroelectrics allow for the tuning of microwave devices by virtue of the nonlinear dependence of their dielectric permittivity on an applied electric field. Experiments on the field-polarization dependence of ferroelectric thin films show variation in dielectric permittivity of up to 50%. This is in contrast to the conventional dielectric materials used in electrical devices which have a relatively constant permittivity, indicative of the linear field-polarization curve. Ferroelectrics, with their variable dielectric constant introduce greater flexibility in correction and control of beam shapes and beam direction of antenna structures. The motivation behind this research is applying ferroelectrics to mechanical load bearing antenna structures, but in order to develop such structures, we need to understand not just the field-permittivity dependence, but also the coupled electro-thermo-mechanical behavior of ferroelectrics. In this paper, two models are discussed: a nonlinear phenomenological model relating the applied fields, strains and temperature to the dielectric permittivity based on the Devonshire thermodynamic framework, and a phenomenological model relating applied fields and temperature to the dielectric loss tangent. The models attempt to integrate the observed field-permittivity, strain-permittivity and temperature-permittivity behavior into one single unified model and extend the resulting model to better fit experimental data. Promising matches with experimental data are obtained. These relations, coupled with the expression for operating frequency vs. the permittivity are then used to understand the bias field vs. frequency behavior of the antenna. Finally, the effect of the macroscopic variables on the antenna radiation efficiency is discussed.

Paper Details

Date Published: 31 March 2009
PDF: 9 pages
Proc. SPIE 7291, Nanosensors, Biosensors, and Info-Tech Sensors and Systems 2009, 729110 (31 March 2009); doi: 10.1117/12.816411
Show Author Affiliations
Prashanth Ramesh, The Ohio State Univ. (United States)
Gregory N. Washington, The Ohio State Univ. (United States)

Published in SPIE Proceedings Vol. 7291:
Nanosensors, Biosensors, and Info-Tech Sensors and Systems 2009
Vijay K. Varadan, Editor(s)

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