Microwave and Millimeter Wave Balanced Antipodal Vivaldi Antennas for Imaging and Ultrawideband Localization Applications

Abstract

The need for better radiating elements designated for ultrawideband performance newlineis continuously on the rise. Parallelly, the design challenges also become multi-fold newlinerespectively. This thesis discusses five distinct Balanced Antipodal Vivaldi Antennas newline(BAVA) each with its unique advancement. The first contributory chapter introduces a newlinenew BAVA with asymmetric meshed ground and a quarter-wave labyrinth director. It newlinehas aimed to improve the deflection angle of the principal E-plane. The evolution of newlinethe antenna from basic BAVA to the proposed model is analysed for each stage from newlineone to four. Radiation characteristics including S11, side-lobe level, cross polarization newlineand boresight-gain are simulated. The rate of change of deflection angle is effectively newlinecontrolled by an eight-loop structured square labyrinth shaped metallic director newlinethat is placed between the radiating flares. Furthermore, the impedance matching of newlinethe proposed antenna is significantly improved with the meshed ground configuration. newlineParametric studies on labyrinth positioning, via placement, and meshing sizes are also newlineinvestigated. Group delay is also measured to be in acceptable range as recommended newlinefor a typical ultrawideband antenna. The propagating modes are analysed and ensured newlinethat the operating frequency band of the proposed antenna is well isolated from higher newlineorder modes. The second contributory chapter proposes a BAVA with sliced fins and newlinea quarter-wave labyrinth director aiming to arrest the sidelobe level when compared to newlinethe conventional BAVA. This is achieved through the slicing of the fins of the all three newlineradiating flares with a design criterion that satisfies to avoid standing wave formation. newlineIn addition, combined with the sliced fin configuration, the labyrinth is focusing the newlineelectromagnetic energy in the boresight direction thus rectifying the beam-squint on the newlineE-plane of the proposed antenna. Consistent radiation patterns are observed while maintaining newlinesignificant gain throughout the operating band of frequencies.