Accurate Effective Permittivity Calculation of Printed Center-Fed Dipoles and Its Application to Quasi Yagi-Uda Antennas

A closed-form method that accurately calculates the effective permittivity as seen by printed center-fed dipoles is presented. That accurate prediction enables the correct choice of the required dimensions of the dipole for a certain resonant frequency. For quasi Yagi-Uda antennas that usually have the driven element as a center-fed dipole, this means an accurate prediction of the required length of the driver, and subsequently all the other dimensions of the antenna without the need for extensive simulations and optimizations. The results obtained by full-wave electromagnetic simulations and measurements, over a wide range of design parameters, prove the validity of the derived method, which is based on the conformal mapping. The proposed method gives the correct estimation of the lengths of the dipoles with less than 10% error compared with the optimized design values. The conventional method results in estimations with as much as a 50% error.