S-Band Cylindrical Structural Antenna of Small Diameter with Radial Modes Using Aperture Coupled Feeding

This paper deals with the design of cylindrical structural antennas that operate using radial modes to achieve efficient and compact radiating antennas. Structural antennas are employed to make the load-bearing structures directly resonate, such as carriers used in aerospace and automotive applications. With this it is possible to get a very low-profile antenna and benefit from a bigger resonant surface. However, a significant challenge with these antennas is the emergence of higher-order modes when the wavelength is small relative to the size of the structure, which disrupts optimal operation. Radial modes are characterized by their quasi-insensitivity to the length of the cylinder, thus would be very relevant with those. A novel approach is proposed to excite these modes with aperture coupled feeding, helping to stabilize the antenna feeds and optimizing the number of exciters needed and, by extension, the structural impact. Simulations conducted using the CST full-wave solver demonstrate that the antenna achieves a bandwidth of 3.6% and a peak gain of 5.5 dBi in the S-Band. These results suggest that this approach enables the integration of antennas into cylindrical structural components without compromising electromagnetic performance, offering promising potential for multifunctional systems that combine the use of multiple modes.