Investigations on the design of performance enhanced antipodal vivaldi antennas

Abstract

Vivaldi antennas are one of the best choices for wide impedance bandwidth, planar configuration and low profile. A typical Vivaldi antenna has end-fire radiation characteristics and has two variants such as coplanar and antipodal configuration. For stealth applications, the conventional Vivaldi Antennas and Antipodal Vivaldi Antenna (AVA) are preferred due to its attractive impedance and radiation characteristics. Unlike the coplanar configuration, AVA has many advantages such as simple feeding technique and large impedance bandwidth. Furthermore, one important aspect to be considered for stealth application is its radar signature.The antennas used for stealth applications should have fewer reflections when deployed in an electromagnetic environment to make the antenna merely undetectable. For such requirements, broadband meta-surfacesare widely discussed. The meta-surfaces uniformly diffuse the reflected wavesand RCS reduction is achieved. However meta-surface integrated antennas become bulky and therefore simple RCS reduction techniques are required. Object shaping is one popular technique which removes the portion of the conductor which does not effectively contribute to the impedance and radiation characteristics of the antenna. In this thesis, the radar cross-section RCS performance enhancement of AVAs is considered along with size reduction since many reported works deal with RCS reduction in conventional single layer Vivaldi antennas.The first section of the research presents the design of a compact AVA with reduced RCS for directional UWB communications. The impedance characteristics of a conventional AVA are improved by introducing a balun taper newline