A solgel method was used to prepare Ca x Zn (1Àx) Al 2 O 4 thin films and fabricate GPS patch antennas. The addition of calcium (Ca) has increased the e r , crystallite size, and grain size, to increase the ceramics density. The three highest Q 9 f values appear at the position of x = 0.05 (31,091 MHz), 0.15 (63,906 MHz), and 0.25 (40,609 MHz), respectively. The best combination of microwave dielectric properties (e r~9 .02), Q 9 f~63,906 MHz and with the lowest return lost (À25 dB) is obtained for specimen using Ca 0.15 Zn 0.85 Al 2 O 4 (x = 0.15) ceramics, which is the suggested material for GPS patch antennas.

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Zn (1 -x) Ti x Al 2 O 4 -based microwave dielectric ceramics were prepared by sol-gel method. The obtained compounds were characterized and fabricated as GPS patch antennas. The XRD patterns show a three-phase system with a spinel ZnAl 2 O 4 , anatase and a rutile (TiO 2 ). The addition of TiO 2 increased the crystallite size and grain size, and surface morphology tended to increase the ceramics density (4.61-4.75 g/cm 3 ) and dielectric constant, e r (8.56-13.51). Based on the material investigated and microwave antenna theory, GPS patch antennas were fabricated using Zn (1 -x) Ti x Al 2 O 4 and then measured using a PNA series network analyzer. The surface of the GPS patch antennas and ground plane was coated with 200-nm-thick silver to enhance ohmic contact. The patch antenna sizes decreased as e r increased from 2.88 9 4.37 cm (12.58 cm 2 ) to 3.53 9 2.21 cm (7.80 cm 2 ). Among these antennas, the Zn 0.70 Ti 0.30 Al 2 O 4 shows an excellent performance combination between return loss (-28.71 dB), small size (3.53 9 2.21 cm), and wide bandwidth (270 MHz). Graphical Abstract