Bandwidth Improvement of Reflectarray Antennas Using Closely Spaced Elements

A bandwidth improvement method in re∞ectarray anten- nas by using closely space elements, i.e., unit-cell sizes smaller than ‚/2, has been investigated both numerically and experimentally in this paper. A new deflnition of phase error has been introduced to analyze the broadband mechanism of closely spaced phasing elements. Through full wave EM simulations, it is revealed that closely spaced elements achieve a smaller phase error over the band. Based on these theoretical studies two Ka-band re∞ectarrays were fabricated and their performance was measured across the frequency range of 30 to 34GHz. It is demonstrated that the re∞ectarray designed with closely spaced elements achieves a notable improvement in gain bandwidth perfor- mance.