Operability of Folded Microstrip Patch-Type Tag Antenna in the UHF RFID Bands Within 865-928 MHz

Abstract

The solution of a boundary-value problem formulated for a modified Kretschmann configuration shows that the phase speed of a surface-plasmon wave guided by the planar interface of a sufficiently thin metal film and a chiral sculptured thin film (STF) depends on the vapor incidence angle used while fabricating the chiral STF by physical vapor deposition. Therefore, it may be possible to engineer the phase speed quite simply by selecting an appropriate value of the vapor deposition angle (in addition to the metal and the evaporant species). © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1966 -1970, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop. 23511Key words: Kretschmann configuration; metal optics; sculptured thin film; structural handedness; surface plasmon INTRODUCTIONThe solution of a boundary-value problem formulated for a modified Kretschmann configuration has recently shown that a surfaceplasmon wave can exist at the planar interface of a sufficiently thin metal film and a nondissipative structurally chiral medium, provided the exciting plane wave is p-polarized [1]. Surface-plasmon waves in the visible and the near-infrared regimes are being exploited nowadays for sensing, imaging, and other applications [2][3][4][5]. Structurally chiral mediums exist as chiral nematic and chiral smectic liquid crystals [6] as well as chiral sculptured thin films (STFs) [7].In addition to their structural handedness (left or right) and their structural period along the axis of helicoidal nonhomogeneity, chiral nematic liquid crystals are characterized by two relative permittivity scalars: ⑀ a and ⑀ b . Chiral smectic liquid crystals and chiral sculptured thin films, however, are characterized by three relative permittivity scalars (⑀ a , ⑀ b , and ⑀ c ) as well as a tilt angle ʦ ͓0,/2͔. Our focus here is on chiral STFs, which are fabricated by physical vapor deposition [7].The constitutive parameters of a chiral STF can be substantially engineered by controlling a few deposition variables. While a chiral STF is being grown on a planar substrate, its structural handedness and structural period are controlled by substrate rotation, whereas a vapor incidence angle v ʦ ͑0,/2͒ largely controls ⑀ a,b,c and . Therefore, it may be possible to engineer the phase speed of a surface-plasmon wave at the planar interface of a thin metal film and a chiral STF in the Kretschmann configuration [8] quite simply by selecting an appropriate value of v (and the metal as well as the evaporant species, of course).That thought engendered this communication. Section 2 contains a brief description of a modified Kretschmann configuration, wherein the combination of the metal film and the chiral STF is sandwiched between two half-spaces occupied by the same isotropic dielectric material that is optically denser than the chiral STF [1]. Section 3 contains numerical results to show that a higher value of the vapor incidence angle reduces the phase speed of the surface-plasmon wave ...

Thin ultra high-frequency platform insensitive radio frequency identification tags

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An Accurate Method for Impedance Measurement of Rfid Tag Antenna

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