A Low-Profile Quad-Beam Transmitarray

In this letter, a novel method is proposed to design a low-profile multibeam transmitarray. Instead of a conventional horn feed, a slot array (SA) feed is used to illuminate uniformly same size transmitarray aperture (TA) in near field with a plane wave excitation, andTAis designed to transform plane wave to high gain multibeam pattern. The separation between SA feed and TA is independent of aperture size, so a very small separation is selected to achieve a low-profile transmitarray. A quad layer 3-dipole unit cell with 360 degrees phase shift range is used as a transmitarray element. A modified intersection approach is used to optimize distribution of transmitarray elements on aperture to synthesize multibeam pattern. Finally, a prototype of Ku-band quad-beam transmitarray antenna is fabricated and tested. The designed transmitarray shows good quad-beam performancewith reduced profile and good match has been observed between simulated and measured results.