High Gain Top Loaded Helical Antenna

This paper presents a technique to achieve high gain in helical antenna is addition to broadband width. The proposed helical antenna operates in axial mode and will generate a radiation beam along the helical axis. In order to improve the gain characteristics a circular metal disc is placed on top of the helical antenna at a small distance from the helical line. The current in the helical line along with the current in the circular disc, generate a concentrated axial beam. The antenna achieves more gain with few number of turns, thus resulting in small size. The proposed antenna is fabricated and experimentally tested. It achieves good -10dB impedance bandwidth from 2.3 GHz to 2.84 GHz (500 MHz), good axial ratio bandwidth from 2.3 GHz to 2.9 GHz (600 MHz) and gain of 10.46 dB with good radiation pattern characteristics. The proposed antenna generates circular polarized waves resulting in promising structure for wide range of applications.