A simple cavity method which increases bandwidth of cylindrical dipole antennas to almost 100%

Abstract

A broadband dipole antenna and an integrated cavity section responsible for increasing bandwidth are introduced, designed, and successfully fabricated. This simple and highly effective cavity is added at the dipoles input, where the concentric coaxial feed line becomes its inner conductor, and the dipoles cylinder becomes its outer conductor. This coaxial-fed dipole antenna could be easily fabricated due to its simple mechanical structure. A version of this type of dipole antenna, with a total length of less than 38 cm (0.44λ) and a radius of about 5 cm, is designed once symmetrically and once with an asymmetrical down-tilted radiation pattern. The new proposed cavity part can increase the antenna's bandwidth up to 100%, which is highly superior compared to conventional counterparts. Furthermore, the antenna's radiation pattern is stable throughout the bandwidth. The minimum realized gain at the solid angle of θ (for instance, θ between 90 and 120°) is perfectly above zero within the frequency range. The antenna measurement results are in acceptable agreement with the simulations.