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Communication & Space
Sciences Laboratory

Conformal Antennas

E-Textile Antennas

e-textile (conductive fabric) monopole antenna

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1-) The Radio Frequency Characterization of Conductive Textile Materials: A Preliminary Step for Accurate Antenna Modeling
by R. Shaw, B. R. Long, D. H. Werner, and Arthur Gavrin

ABSTRACT: There is much recent interest in antennas constructed from conductive fibers and textiles. Traditionally, antennas are constructed with metallic elements which are sufficiently conductive that they can be treated as PEC with little loss of accuracy. However, the new conductive textile materials have electrical properties sufficiently different from standard metallic conductors to affect the accuracy of computer modeling and analysis. Accurate antenna modeling requires knowledge of the effective conductivity of the textile antenna elements, a topic that has not been adequately addressed to date in much of the available literature. This work presents an experimental method for the determination of the radio frequency parameters for conductive textile materials and shows how such experimentally derived material parameters can be used to enhance the accuracy of computer antenna designs and models.

2-) The Characterization of Conductive Textile Materials Intended for Radio Frequency Applications
by Robert K. Shaw, Bruce R. Long, Douglas H. Werner, and Arthur Gavrin

ABSTRACT: Antennas constructed in part from conductive textile materials (also known as e-textiles) by means of standard textile manufacturing techniques are currently receiving increasing attention from antenna theorists and antenna manufacturers alike. However, due mostly to the unique fabrication methods employed, these novel materials cannot be treated as simple, equivalent substitutes for the more-conventional metallic antennas. Conductive yarns can have considerably less-than-ideal conductivity, and their inhomogeneous internal structure, with features small with respect to the skin depth, can be difficult to analyze directly in terms of conductive-material bulk resistivity. Furthermore, the undulating and sometimes non-planar nature of stitched or woven conductive textile yarns introduces a significant phase delay that must be properly taken into account. This article describes a method to determine the conductivity, &sigma, which accurately represents a lossy inhomogeneous textile conductor for a MoM segment having the same radius as the actual conductive yam. This method has three steps. First, the resistance per unit length of the textile conductor is determined experimentally, in a transmission-line test cell. Next, this measured resistance per unit length is adjusted to account for the nonuniform current distribution across the multiple yarn conductors. Finally, a surface-impedance formulation is employed to derive an equivalent MoM-segment bulk conductivity that accurately represents the measured conductor's performance. Excess phase delay, inherent in textile conductors, is determined by examination of the phase component of the test cell scattering parameter, S21.

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