Near optimal synthesis of exponential log-periodic dipole array geometry by applying invasive weed optimization

Abstract

A new geometry of log-periodic dipole array (LPDA) is presented in this work. Unlike the traditional LPDA geometry, where all dipoles are considered to be inside the same angular sector, the proposed LPDA adopts an exponential geometry, described by two parameters called exponential scale factor and exponential relative spacing. By properly adjusting these two parameters, the exponential LPDA (ELPDA) geometry obtains wideband behavior with excellent radiation characteristics. A near optimal ELPDA geometry that achieves the desired radiation characteristics inside the required bandwidth is found in the present work by applying a recently developed method called invasive weed optimization (IWO). In particular, the ELPDA is required to operate in the 800-3300MHz frequency range under specific constraints concerning standing wave ratio, forward gain, gain flatness, front-to-back ratio and side lobe level. A comparison with a traditional LPDA of the same total antenna length exhibits the superiority of the proposed geometry.