Diffraction from multifilar wire helix grating

Le résumé fourni par la source

.. . Theory of multifilar helix gratings had been proposed, in [ 11. Using the wellknown representation of multifllar helix as a perfect anisotropically conducting screen the authors have obtained rigorous solution to the problem of diffraction of a normally incident elliptically polarized plane wave by the infinite grating of helically conducting cylinders. Grating characteristics we determined by three independent parameters: pitch angle a, spacing nonnalized to the wavelength s=pJil, and fillfactor .(helix diameter divided by the spacing) q=d/p. Analysis of the numerical results for various a, s, and Q gives the following possible applications of the ' helix gratings in .mfcrowav.e engineering (the helices are assumed to be right-handed). 1. C)ircular wolarization-filtey For the parameters a=35O, s=0.38, ~0.87, one can observe total reflection of the left-handed circularly polarized wave, whereas the right-handed wave is partially transmitted, The phase of the reflection coefficient of the right-handed wave is zero. Consequently, due to the transmission type resonance, the pair-of the identical gratings with the above parameters separated by the distance kd/2 (n= 1,2,3.. .) totally transmits the right7handed circularly polarized wave and totally reflects the left-handed wave. 2. Circular wolurizer - power divider At specified values Qf the parameters a, s and q, the helix grating under consideration divides the power of the incident linearly polarized wave into two parts, with the both transmitted and reflected waves being circularly polarized and having opposite handedness. Reflected wave handedness coincides with the helix handedness. Numerical results show that, at, e.g., a=75O, s=0.23 and q=0.34. the required conditions are satisfied. 3. Isotrowic twist polarizer Unlike an anisotropic twist polarizer, the helix grating can rotate polarization of a linearly polarized wave through a given angle when electric vector of the incident wave is arbitrarily oriented with respect to the grating conductors. Indeed, when the helix ,grating with the parameters a =26.3O, s=0.68, and q=0.57 is illuminated by a: circularly polarized plane wave, the. transmitted wave is circularly polarized as Well, with the polarization being retained. The right-handed and left-handed transmitted waves have equal magnitudes and different phases. Thi phase shift determines that the angle of polarization plane rotation is 39O.

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