BANDWIDTH IMPROVEMENT OF REFLECTARRAYS USING SINGLE-LAYERED DOUBLE CONCENTRIC CIRCULAR RING ELEMENTS ON A SUBWAVELENGTH GRID

摘要

This article proposes the use of double concentric circular ring elements arranged in a subwavelength grid on a single layer of substrate, in an effort to increase the bandwidth of reflectarrays. Compared to the traditional λ/2 grid arrangements, radiating elements arranged in subwavelength grids achieves a more similar behavior over wider frequency bands when radiating elements' parameters are varied; albeit with a smaller reflected phase range. Furthermore, in contrast to conventional subwavelength single-patch designs that have only one variable parameter of the phasing element, the double concentric circular ring elements also allow additional degrees-of-freedom to improve the bandwidth. Based on the concentric ring element, two offset-fed 0.43 × 0.43 m~2 reflectarrays, one with λ/2 grid and another with λ/3 grid, centered at 10 GHz are designed and developed. The measured results show that the 2-dB gain bandwidth of the one with λ/2 grid spacing is 13.6%, whereas the one with λ/3 grid spacing is 24.4%.