Synthesis of magneto-dielectrics from first principles and antenna design

Abstract

Magneto-dielectric materials have been spotlighted as a new opportunity for effective antenna size reduction in many recent studies. In this paper, we start from first principles to describe the methodology used to synthesize the magneto-dielectric material. A combination of Bruggeman's effective medium model and Sihvola and Lindell model are used to find the right mixture of cobalt particles and fluoropolymer material for the effective antenna miniaturization. A three pole Lorentzian dispersion model is derived for fitting extracted material properties of magneto-dielectric composite material. The material properties are extracted using a cavity perturbation technique with substrate integrated waveguide cavity resonator. The Kramers-Kronig relations are used to demonstrate that the extracted material properties from the method are causal in this paper. A 900MHz PIFA on magneto-dielectric material substrate is designed, fabricated and measured. A 7.4% bandwidth and 61.7% radiation efficiency for the antenna were obtained. Human body effect to antenna was studied and Specific Absorption Rate (SAR) was calculated. The simulation results show that magneto-dielectric material can reduce the effect of human body on antenna performance and the magnetic loss enables a decrease in the SAR of the antenna.