Impact of Feed Position on the Operating Band of Broadband Reflectarray Antenna

In this letter, the effect of moving the feed on the operation bandwidth of a broadband reflectarray is investigated through simulation and measurement. A new broadband cell element with optimized dimensions to achieve linear phase shift is proposed in this investigation. A square reflectarray of 40×40 cm² comprising this particular unit cell was designed and fabricated to demonstrate wideband operation at X-Ku band. The effect of feed movement on the operating band was studied by exciting the reflectarray with a plane wave and monitoring the near field on the line passing through the assumed feed locations over a wide frequency band. Considering three different feed positions, the reflectarray was simulated, and good agreement between simulated and measured results was observed. It is shown that changing the feed location leads to a considerable shift in operating frequency window of the reflectarray and also its maximum gain, which gives rise to the possibility of changing the operating band without redesigning the reflectarray by only moving the feed. Moreover, a remarkable value of 36% of 1.5 dB gain-bandwidth was measured, which is higher compared to previously reported designs in the literature.