A broadband linearly polarized single-layer reflectarray antenna constructed by element cells of triple gapped rings with phase-delay lines (TGR-PDLs) attached to the outer one is presented in this communication. The novel TGR-PDL element is composed of three circular rings, each with a pair of gaps which are orthogonally positioned, and two identical PDLs are attached to each half of the outer ring. The characteristics of the proposed element are first analyzed and then a linear and smooth phase response covering about 600 degrees is obtained by adjusting the length of the PDL. Based on the element cell, an offset-fed reflectarray antenna of an octagon-shaped aperture with 266 mm in diameter is designed, fabricated, and measured to verify the broadband property of the proposed element. The measurement results show that about 31.5% of 1-dB gain bandwidth is realized, and the maximum gain at the center frequency of 10 GHz is about 25.78 dBi, which is equivalent to about 50% aperture efficiency.
