A Thin Reflective Diffraction Grating Employing Resonant Structures

Abstract

Reflective diffraction gratings consist of a periodic threedimensional structure that produces appropriate constructive and destructive interference in order to redirect an incoming wave as a function of frequency. Depending upon the angle of incidence, the thickness required for this structure can range from a fraction of a wavelength to several wavelengths. While such a thickness does not present a problem for optical applications, it can make the diffraction grating very bulky for radio applications, notably in the lower frequency bands. This communication presents a new thin diffraction grating, employing resonant structures, whose thickness is only 1/34th of a wavelength. Simulations and measurements are presented for a thin diffraction grating, designed to operate in the VHF band in unfavorable outdoor conditions. Abstract-A new single-layer linear-to-circular polarizer is presented in this communication. A novel hybrid meander line and loop configurationis employed to transform linearly polarized field to circularly polarized field over a wide frequency band. Numerical simulations indicate that the proposed polarizer is robust under oblique and deflected illuminations. A prototype of the proposed polarizer is designed and fabricated. Measured results show that the band of axial ratio less than 3 dB ranges from 18 to 29 GHz with about 3-dB insertion loss.