ON THE DESIGN OF PATCH ANTENNAS TUNED BY TRANSVERSELY MAGNETIZED LOSSY FERRITE INCLUDING A NOVEL RESONATING MODE

Circularly symmetric patch antennas tuned by trans- versely magnetized lossy ferrite are studied. The circular and ring patch geometries printed on ferrite substrate or tuned by ferrite post and ferrite toroid are studied. Both saturated and partially magne- tized ferrite are considered. Strong effects on the dispersive properties of modes propagating under the patch and in turn on the antenna resonant frequency and input impedance are observed when the ferrite losses are taken into account. The patch antennas resonance at a novel mode propagating in the traditionally assumed switch-off frequency range of negative effective permeability constitutes an essential origi- nal contribution of this work. In all cases the dynamic control of the patch resonant frequency through the DC-biasing field is investigated. The "perfect magnetic walls approximation" was employed in the anal- ysis since it offers a valuable physical insight as well as simplified closed form expressions for the resonant conditions. These are used as engi- neering design formulas for an initial antenna design, which is in turn fine tuned with the aid of a numerical simulation-optimization scheme. The validity of the present method was verified through comparisons with published experimental results and numerical simulations.