Ceramics for antennas in next-gen wireless communication networks

People around the world have benefitted tremendously from the steady advancement of communication technologies.¹ Innovations in this field allow consumers to access GPS navigation directions that account for current traffic conditions, receive real-time alerts on impending natural disasters, and monitor their health via remote sensors, among other benefits.

Since 2019, rollouts of the next technological leap in communication systems—fifth generation (5G) mobile networks—are gathering momentum globally. Compared to the former generation, 5G networks are expected to provide data rates that are 10 times faster,² as well as lower latency and larger bandwidths to support the ever-increasing volume of data transmission.

To achieve these improvements, 5G devices operate at higher frequencies than 4G devices. While both 4G and 5G networks can operate in the same lower band of the spectrum (400–700 MHz), the 4G network only operates up to frequencies of 2.7 GHz. In contrast, the 5G network can operate in mid-band frequencies (3–5 GHz) as well as in several higher mm-wave bands (24.3–71 GHz).³

Currently deployed 5G systems operate predominately in the mid-band frequencies. Researchers are working to address the considerable technological challenges that hinder wide-scale adoption of mm-wave technology.

For instance, electromagnetic waves cannot travel as far at higher frequencies, which therefore reduces coverage area substantially. Higher densities of smaller base stations and repeaters will be needed to overcome this limitation. Additionally, base stations that transmit mm-waves are expected to have narrower beams that are steered to locations of demand rather than broad beams that cover areas indiscriminately.

Multiple-input multiple-output (MIMO) technology is one way of accomplishing this change to base station operation. In MIMO systems, antennas are composed of an array of several smaller radiating elements, which can alter the shape of the global radiation pattern based on demand.

The radiating elements in MIMO antennas can be made of metal, polymer, or ceramic. Metallic antennas have lower efficiencies due to high conduction losses, especially at mm-wave frequencies, so ceramic or polymer dielectric resonator antennas (DRAs) are more suitable for this application. Ceramics specifically are suited for this application because, compared to polymers, they provide better mechanical and thermal stability, superior heat dissipation, lower losses, and flexibility of chemical composition.

To ensure that a DRA operates reliably, its resonant frequency should only experience minimal drift with temperature changes. This stability can be achieved by using a ceramic resonator with a near-zero temperature coefficient. Additionally, for any given material, dielectric losses will increase with frequency. So, materials that maintain extremely low losses at high-band frequencies must be identified. Finally, miniaturization is a trend in many electronics fields, and the use of higher permittivity materials allows for the creation of compact antennas that operate in the mid-band frequencies. However, to achieve resonance at mm-wave frequencies in compact antennas, the ceramic resonator must have a low permittivity.

Multicomponent ceramics, such as silicate-based compounds,⁴ are being investigated to meet the requirements for these mm-wave applications. Plus, with the advent of precision ceramic 3D printing, researchers can begin to envision printing and sintering net-shape parts with exact dimensionality, including geometries that could not be realized by conventional ceramics processing.

My research currently focuses on materials for miniaturized DRAs in mid-band 5G frequency applications. But my group is transitioning to materials for mm-wave communications, including 3D printing ceramic resonators for DRAs.

About the author:
Matthew Julian is a second-year Ph.D. student in L’Institut d’Electronique et des Technologies du numéRique at the University of Rennes, France. He studies ceramics and thin films for 5G antenna applications. Outside of research, he enjoys traveling and watching soccer.