There is an ever-growing need for speed and reliability of wireless communication systems. Addressing the complexity of such systems is therefore a much more daunting task than it was a decade ago. For example, there are multiple radios operating at the same time in a state of the art smartphone. With the imminent advent of 5G wireless communication networks and beyond, transmission frequencies are expected to reach beyond 10 GHz. Low-noise amplification and selection of specific frequencies (filtering) are crucial processes on signals received from the antenna. Conventional passive acoustic filter technologies are not capable of efficiently addressing the needs of such complex systems, especially at high frequencies. The proposed work investigates a new class of devices that will provide simultaneous low-noise amplification and filtering of radio frequency (RF) signals. The ability to integrate multiple RF front-ends on a single chip will enable a host of unprecedented possibilities in wireless communication systems. Individual devices can revolutionize receiver front-end architectures and pave the way to more sophisticated radio systems. This new class of electronic devices can open up a new area of research and development with great potential for commercial applications.
The technical focus of this project is to further explore and enhance the concept of phononic amplification in electromechanical resonant devices for development of narrow-band active filters with frequencies in the GHz range. Such devices can significantly simplify and improve RF front-ends by eliminating the conventional semiconductor amplifiers and moving the amplification into the acoustic domain, where frequency selection takes place simultaneously. Phononic amplification is based on carrier-phonon constructive interference effect in micro to nanoscale mechanical resonant cavities and is in many ways the acoustic equivalent of LASER and Optical Amplification. Absorbing power from an external electrical power source, mechanical vibrations (phonons) can be amplified due to carrier-phonon interactions. The result in the electrical domain is a negative electrical equivalent resistance within a narrow bandwidth around the resonance frequency of the mechanical structure. A negative resistance in combination with a resistive load can act as an amplifier absorbing power from the pump source and delivering amplified RF power to the load. Highly selective filtering provided by the phononic amplifiers can significantly relax the dynamic range requirement and therefore power consumption of RF analog to digital converters. Phononic amplifiers are therefore well suited for modern RF transceivers with direct sampling architectures, in which the RF signal is processed without being down-converted. To meet the linearity and power handling requirements, two-dimensional mechanically coupled (electrically parallel) arrays of such devices will be designed and implemented.
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.
