Computer-aided design of small patch antenna using (Al, Mg)TaO2 ceramics

Abstract

The microwave dielectric properties of (1-x)(Al1/2Ta1/2)O-2-x(Mg1/3Ta2/3)O-2 (AMT) (0less than or equal toxless than or equal to1.0) ceramics and the design of small coplanar waveguide fed antenna (CPWFA) have been investigated. (Al1/2Ta1/2)O-2 and (Mg1/3Ta2/3)O-2 have orthorhombic and tetragonal structure, respectively. As (Mg1/3Ta2/3)O-2 concentration increased, AMT ceramics transformed into the tetragonal structure. Specimens having tetragonal single phase could be obtained above x=0.6. As (Mg1/3Ta2/3)O-2 concentration increased, the grain size, dielectric constant (epsilon(r)) and quality factor (Q) significantly increased and the temperature coefficient of resonant frequency (tau(f)) changed from negative to positive. The tau(f) of 0 ppm C-degrees(-1) was realized at x=0.65 and the Q.f(o) value and epsilon(r) for this composition were 112 470 GHz and 26.1, respectively. Newly developed 0.35(Al1/2Ta1/2)O-2 - 0.65(Mg-1/3 Ta-2/3)O-2 dielectric materials were used for 1.5 GHz band CPWFA design and fabrication. The size of the CPWFA can be reduced by using high dielectric constant AMT ceramics, insetting slits into the patch, and fabricating CPW feed line in the ground plane. The slits play a role in not only lowering a center frequency but also fine tuning for the proposed antenna together with the open stub of CPW feed line. The CPWFA with slits has a lower center frequency than the conventional CPWFA, which suggests that the antenna size can be reduced by as much as 16.3%. The structure simulations of the CPWFAs have been performed to obtain impedance matching and to investigate the effects of slits. Experimental results of the fabricated device were in good agreement with the simulation. (C) 2002 Kluwer Academic Publishers.