Researchers from the Swiss Federal Institute of Technology in Lausanne (EPFL), led by Silvan Stettler, have introduced a novel device called the bulk acoustic resonator with vertical electrodes (VBAR). This innovation aims to address the growing demands of radiofrequency (RF) front ends for current and next-generation wireless communication systems, including 5G and 6G.
The study, published in the journal Nature Communications, focuses on the need for acoustic filters that can combine wide bandwidth, high power capability, and thermal stability. Existing technologies, such as surface and bulk acoustic wave (SAW and BAW) devices, often face trade-offs between electromechanical coupling, lithographic tunability, and robustness. The VBAR device seeks to overcome these limitations by combining the advantages of both suspended and solidly mounted resonators.
The VBAR utilizes lithium niobate (LiNbO3) ridges with sidewall electrodes to excite a shear-horizontal bulk acoustic resonance. This design allows for frequency control through lithography while maintaining mechanical anchoring to the substrate. The researchers fabricated VBARs that exhibited electromechanical coupling coefficients exceeding 30% in the 2-4 GHz range. This high coupling enables the creation of ladder filters with fractional bandwidths of nearly 20%.
While the VBAR concept shows promise, the researchers note that further optimization is necessary to minimize losses. Despite this, the VBAR offers a potential alternative route toward wideband and robust RF filters for next-generation wireless systems. The practical applications for the energy sector could include improved efficiency and reliability in wireless communication networks, which are crucial for smart grid technologies and other energy management systems.
The research highlights the ongoing efforts to enhance RF filter technology, which is essential for the development of advanced wireless communication systems. As the demand for higher data rates and more reliable connections grows, innovations like the VBAR could play a significant role in meeting these needs.
This article is based on research available at arXiv.