Breaking the Barrier for Acoustic Resonators: High Performance Filters at Millimeter Waves

Communication standards at millimeter waves are meant to revolutionize society by facilitating high speed data links for augmented and virtual reality, unmanned air vehicles and self-driving cars, remote health and infrastructure monitoring, and the broader Internet of Things. The millimeter wave systems that are being commercialized do not rely on filtering at the antenna element.

It is predictable that as the number of deployed systems will increase, interferers and hence the lack of filtering will be a bottleneck for these communication systems, resulting in large power consumption by the baseband electronics. As more millimeter wave systems are deployed, and the spectrum is getting congested, increase power consumption will be required to handle interfering signals.

The needs to eliminate interferers through mm-wave filtering at the antenna element will become a fundamental bottleneck to further deployment of these networks. The design and implementation of bandpass filters at these frequencies in the form factors required by on-chip/portable/wearable devices is particularly challenging. This research project proposes to use acoustic elements to deliver sharp filtering directly at each antenna element.

If successful, this project will have broader impacts beyond the specific millimeter wave applications proposed herein. By overcoming the fundamental challenges associated with the design and synthesis of millimeter wave acoustic resonators, the research effort will devise a general resonator platform for investigating other phenomena associated with quantum information science, computing and sensing.

Extending the range of operation of acoustic resonators to millimeter wave frequencies comes with fundamental questions related to the ability to operate at such high frequency with low loss and appropriate impedance levels. Attaining high performance at millimeter waves is a fundamental barrier for acoustic devices. Answering these questions calls for investigations into materials, nanofabrication processes and resonator designs that challenge the state-of-the-art in acoustic devices.

The intellectual merit of this work consists in: investigating fundamental damping mechanisms in thin films of suspended structures at millimeter waves; devising innovative resonator designs that minimize damping while preserving resonator characteristic impedance matching; and developing nanofabrication methods that enable the co-existence of nanoscale features with micron-scale structures with high yields. The ultimate applied goal of this project is to devise a bandpass filter operating at millimeter waves using an ensemble of acoustic resonators arranged in a conventional ladder configuration.

This project is also investigating various novel techniques for generating two nearby-frequency resonators and for real-time tuning of the filter bandwidth.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.