BANDWIDTH IMPROVEMENT OF REFLECTARRAYS USING SINGLE-LAYERED DOUBLE CONCENTRIC CIRCULAR RING ELEMENTS

Abstract

In an efiort to improve the bandwidth of the single layer re∞ectarray, this paper investigates the use of double concentric circular ring elements arranged in a range of sub-wavelength grids on a single layer of substrate. Compared to the traditional ‚=2 grid arrangements, when the radiating elements are arranged in grids less than ‚=2, the re∞ected phase is more uniform over a wider frequency bands when radiating elements' parameters are varied; albeit with a reduced re∞ected phase range. The double concentric circular ring elements used here also allow an additional degree-of-freedom to improve the bandwidth. A comprehensive investigation on re∞ectarrays' performance with various grid spacings is conducted and the trade-ofi between the re∞ectarray gain and bandwidth is also discussed. Based on the concentric ring element, four ofiset-fed 0:43m£0:43m re∞ectarrays centered at 10GHz with various element periodicities, namely ‚=2, ‚=3, ‚=4 and ‚=5 grids, are designed and developed. The measured results show that among the four re∞ectarrays, the one with ‚=4 grid spacing achieves the broadest 2-dB gain bandwidth of 33% with an aperture e-ciency of 36.2%.