A miniaturized three‐dimensional log periodic Koch‐dipole array antenna using T‐shaped top loading

Abstract

A log periodic dipole array antenna (LPDA) is miniaturized by using top loading. The Koch dipole further helps to shrink the antenna size. Different from the traditional LPDA that features a planar structure, the proposed log periodic Koch-dipole array (LPKDA) adopts two identical pairs of top-loaded Koch-dipoles that deploy orthogonally along the feed line. This results in a tree-like three-dimensional antenna geometry, which introduces one extra dimension of freedom for antenna designers. The influence of the top-loading on antenna's impedance bandwidth is studied under the Wheeler and Chu's limit. The characteristic of the Koch-dipole is analyzed. Taking the advantage of 3D printing technology to fabricate complex models, the proposed LPKDA is printed by selective laser melting using aluminum alloy. The simulated −10-dB bandwidth is 117.4% (0.91-3.54 GHz) The LPKDA has the average gain of 5.3 dBi over the 1 to 3.5 GHz impedance bandwidth in measurement. Radiation patterns agree well in simulation and measurement. Compared with conventional LPDA of the same impedance bandwidth, the proposed LPKDA features 42%-dimensional reduction. This letter proves the feasibility of antenna optimization by using both innovative design method and advanced fabrication process.