Log periodic fractal KOCH antenna for wireless applications

Abstract

In wireless communication system, antenna is one of the important devices to allow two ways communications. At lower frequency bands, the antenna size is bigger compared to the higher frequency band. Various techniques have been used in reducing the antenna size such as fractal technique and higher dielectric constant while maintaining the performance of the antenna. In this work, the fractal Koch geometry has been used as a method to reduce the size of the developed antennas. This is based on the advantages that are inherent for fractal Koch geometry in reducing the size and maintaining the performances. The design of the antenna begins with the understanding of the basic antenna properties such as return loss, radiation pattern including the understanding of the Koch geometry. A number of designs has been developed such as zero, first, second (0th, 1st, 2nd) and series iteration which are targeted for wideband and Ultra High Frequency (UHF). The simulation work is done using Computer Simulation Technology (CST 2008) software. About 27 % reduction of the antenna size has been achieved by using fractal Koch technique. The designs obtained from simulation are fabricated on FR4 board using wet etching technique. The results from simulation and measurement have been compared and analyzed. The antennas show good return loss lower than -10 dB at the desired frequency, directional radiation patterns with beamwidth of 110 degree, wide bandwidth up to 200 %, and gain between 5 dBi and 8 dBi.