Material and geometry effects of dielectric and conductive resonators on rectangular patch antennas

Abstract

The growing demand for compact, lightweight, and high-performance antenna systems has been driven by applications such as the Internet of Things (IoT), wearable electronics, wireless sensor networks, and 5G/6G communication systems. Among the available radiating structures, microstrip patch antennas are widely employed due to their low profile and ease of fabrication; however, their resonant frequency is intrinsically tied to physical dimensions, imposing significant challenges to further miniaturization. In this context, alternative materials and electromagnetic loading techniques based on dielectric and conductive resonators become essential to overcome this limitation without a proportional increase in antenna size. This dissertation numerically investigates the integration of dielectric and conductive resonators into rectangular patch antennas. As a complementary contribution, an unloaded rectangular patch antenna is separately designed, fabricated, and experimentally characterized to validate the electromagnetic models employed. First, a comprehensive comparative study is presented, evaluating fifteen resonator geometries filled with distilled water (DW), glycerin, and graphite under the same reference antenna, substrate, and simulation conditions, showing that antenna performance depends on the combined influence of resonator material and geometry rather than on either factor alone. Based on the insights gained, a dedicated half-torus resonator is subsequently investigated as a loading element for antenna miniaturization, addressing resonant-frequency reduction while preserving the antenna’s original physical footprint. Finally, as a complementary study, a rectangular patch antenna without resonator loading is designed, fabricated, and experimentally characterized on a distinct substrate, allowing the agreement between simulated and measured results to be assessed and the influence of substrate characterization on the accuracy of the employed electromagnetic models to be investigated. The obtained results indicate that suitable combinations of resonator material and geometry provide an effective means of enhancing patch antenna performance and enabling miniaturization, while the experimental characterization of the unloaded antenna highlights the importance of accurate substrate modeling for improving agreement between simulation and measurement.