Broadband reflectarray composed of gap coupled elements with linear phase response

A broadband reflectarray using gap coupled elements composed of a split ring and a dipole is proposed. The phase variation range of the reflected field from the element on a single layer is achieved larger than 418° by changing the dipole length in a split ring of a fixed size. The phase response of the field is proportional to the dipole length with a slow slope. Compared with multilayer elements and aperture coupled elements, it shows good linear phase response of the reflected field. To validate the proposed geometry, a prototype reflectarray is fabricated and measured. The maximum gain is 33.0 dB, and the 3 dB gain bandwidth is 19.0% at the center frequency of 20 GHz.