On the Design of the Optimized Wideband Antenna (OWA) Yagi

A remarkable method is presented for decreasing the VSWR and increasing the gain and front-to-back (rear) ratio over a larger than typical bandwidth for Yagi antennas. This procedure and a direct dipole 50 Ohm feed were discovered by Prof. Breakall in the early 1990s using sophisticated computer global optimization techniques applied to the NEC4 antenna modeling software. He named this technique the Optimized Wideband Antenna (OWA), and it was first used to increase the bandwidth of monopole and dipole antennas by placing one or more parasitic elements close to the driven dipole or monopole, in a manner similar to the well-known sleeve antenna. The lengths and spacings of these extra parasitic wires are then optimized in a global computer algorithm to minimize the peak SWR in a range of frequencies over some band. The first application was a proposed method of covering several bands on a commercial cell phone at the time with several vertical whip antennas. After this preliminary work on dipoles and monopoles, the method was applied to the Yagi antenna. When applied to Yagis, it is possible to increase the percentage bandwidth with very low VSWR, high peak gain, and very low rear sidelobes with this technique.