Multi-element Vivaldi antenna with sum and difference radiation patterns

Abstract

A design of a dual-port multi-element Vivaldi antenna with E-plane pattern diversity is presented in this paper. This design can cover the band of 3.9 GHz to 18 GHz, with a gain increasing from 10 dBi at 3.9 GHz up to 16.5 dBi at 18 GHz. The grating lobes at higher frequencies are mitigated through an increased proximity of the antenna elements in conjunction with reduced mutual coupling. An improvement of the scattering parameters over the wide band is obtained through a combination of various design methods including, increased internal flares lengths, optimal shaping of the inner edges of the antenna, and corrugations on the outer edges. The realized gain enhancement is obtained through adoption of four tapered slot elements and a semicircular dielectric substrate lens, which also provides extra space for elongating the internal flares. The proposed antenna also generates two different radiation patterns based on the excitation phase of the input ports, namely sum and difference radiation patterns. A high degree of beam symmetry is attained with this antenna structure, when the directional pattern corresponds to the differential feeding of the antenna elements by a wideband rat-race coupler.