Metamaterial loaded vivaldi antenna with high gain and equal beamwidths at KA band

A high gain and broadband Vivaldi antenna with end-fire and equal beamwidth radiation pattern at Ka band is presented in this paper. The Vivaldi slot is fed by the microstrip line-to-substrate integrated waveguide (SIW) transformer. The SIW transmission performance is enhanced by another row of metal vias beside the original one. On both sides of the Vivaldi conductor planes, 8 parallel slots with gradually increasing length are etched to improve the front-to-back ratios. Under the microstrip feed line, three pairs of split ring resonators (SRRs) are etched on the ground to suppress the secondary harmonic. In order to improve the antenna gain and obtain the equal E- and H-plane beamwidths, the special designed zero-epsilon metamaterial (ZEM) units are loaded on the Vivaldi slot with a maximum gain increment of 3.4dB being obtained. The antenna exhibits a broad bandwidth of 38.5% at 35GHz ranging from 26.5GHz to 40GHz with the reflection coefficient less than -10dB, and the gain varying between 9.7dBi and 12.2dBi. The proposed antenna is fabricated and measured to validate the design. The measured results are in good agreement with the simulated ones. (c) 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2337-2341, 2016