Abstract
In this study, a flexible substrate for a patch antenna based on nickel aluminate (NiAl
2
O
4
) synthesized by the sol–gel method is presented. Nano-crystalline NiAl
2
O
4
is synthesized by many researchers with several methods, but they have not been explored much for microwave applications. The microwave dielectric properties of NiAl
2
O
4
were investigated to find their employment as an antenna substrate for microwave wave uses. The sol–gel method was employed to synthesize the flexible composite. The establishment of spinel assembly and crystalline dimension were assured using x-ray diffraction analysis. Morphology of the samples was clarified by means of the scanning electron microscopy. Relative permittivity and dielectric loss tangent of the specimen were restrained by a DAK 200 MHz to 20 GHz dielectric measurement kit and obtained as 4.8 and 0.04, respectively. The energy bandgap was found to be 2.8 eV from optical analysis, which implies that the synthesized nanoparticles are semiconductors by nature. The substrate layer was prepared by mixing NiAl
2
O
4
nano-powder with polyvinyl acetate glue dried up by means of heat. The compatibility of the prepared substrate material for making a microstrip patch antenna is investigated by utilizing the finite-difference method based on a computer simulation technology microwave studio. Finally, the patch antenna is fabricated on NiAl
2
O
4
flexible composite substrate employing 200 nm copper coating over that 1 mm thick substrate by magnetron sputtering to the simulation process following the simulation process, which showed outstanding performances, measured through a N5227A PNA microwave network analyzer and offers a wide band of operating frequency of 8–15 GHz in X-band and K
u
-band of microwave frequency spectra. The operating band of frequency can be arbitrarily chosen by modifying substrate and/or radiating elements. The simulated and measured results are matched satisfactorily.