Characterization of Ti_xZn_(1-x)Al₂O₄ thin films by sol-gel method for GPS patch antennae

Abstract

The need for miniaturization and weight reduction of a GPS patch antennae has forced scientists to search for new microwave dielectric materials. The sol-gel method was used to prepare Ti_xZn_(1-x)Al₂O₄-based microwave dielectric ceramic thin films (x = 0.00, 0.10, 0.20 and 0.30) and to fabricate a GPS patch antennae. The phases of ZnAl₂O₄ and TiO₂ co-exist with each other and form a two-phase system, which is confirmed by the X-ray diffraction (XRD) patterns and the Fourier-transform infrared (FTIR) spectra analysis. The addition of titanium dioxide (TiO₂) increased the crystallite size, grain size, surface roughness and apparent density. A material with a higher density tends to increase the dielectric constant (ε _r ), which is suitable for miniaturization of a GPS patch antenna. As the TiO₂ content increased, the ε _r values increased linearly. Finally, GPS patch antennae were successfully fabricated using the ZnAl₂O₄ and Ti_0.30Zn_0.70Al₂O₄ material. The performances and the operating frequencies of the GPS patch antennae were measured using a PNA series network analyzer. The result showed that both patch antennae resonated at frequency of 1.570 GHz and gave a return loss less than -10 dB. The optimal performance of the GPS patch antennae was obtained from the specimen using Ti_0.30Zn_0.70Al₂O₄ (ε _r ~ 14.57, wide bandwidth of 240 MHz and low return loss of -34.5 dB), which meets the requirements of GPS applications.