Millimeter-Wave Beam-Tilting Vivaldi Antenna With Gain Enhancement Using Multilayer FSS

This letter presents a new design of tilted-beam antenna with gain enhancement based on the multilayer frequency selective surfaces (FSSs) for fifth-generation applications. A dual-sided printed FSS element with two C-shaped resonators at the top layer and a slotted circular patch at the bottom side, is proposed. The FSS element holds a size of 0.46 lambda x 0.46 lambda (at 28 GHz). A wideband Vivaldi antenna with an end-fire radiation is used to excite the elements of the FSS layers. The effects of different sizes, number, and the angular rotation of the FSS layers are employed to achieve the best antenna performance in terms of beam-tilting, realized gain, and reducing the sidelobe level (SLL). The best antenna performance is achieved when two unequal-sized FSS layers rotated to 45 degrees and fixed under the Vivaldi. The proposed antenna is fabricated and measured. The obtained measured results show a maximum beam tilt angle of 38 degrees, realized gain of 9 dBi, and SLL at -8 dB. The beam tilt angles are validated with the results obtained using the Snell's law in a multilayer environment and found a good agreement.