Nonreciprocal Nano-Acoustic Spectral Processors: Enabling Chip-Scale Full-Duplex cm-/mm-Wave Front-Ends

The ever-increasing quest for wireless communication capacity along with overcrowding of available spectrum resources calls for development of full-duplex RF front-end modules with extreme frequency scalability to untapped cm- and mm-wave regimes (i.e. 3–300GHz). Realization of full-duplex cm-/mm-wave front-end for wireless systems requires integrated wideband spectral processors with nonreciprocal signal transmission for self-interference suppression. Conventional acoustic spectral processors (ASP), such as band-select filters based on film bulk acoustic resonators, have been essential building blocks enabling wireless transceivers. These components, however, are fundamentally limited by their governing physics to reciprocal operation and only efficient at low frequencies (sub-6GHz). This talk introduces transformative nano-acoustic technologies that surpass fundamental limitations of current ASP and enable realization of nonreciprocal spectral processors with extreme frequency scalability to cm- and mm-wave regimes. The new technologies are based on the integration of atomically-engineered piezoelectric and ferroelectric transducers on planar and fin single-crystal semiconductor nano-acoustic waveguides. These architectures enable extreme frequency scaling of ASP to cm-/mm-wave, while sustaining low-loss and wideband operation. The new technologies enable the use of linear and nonlinear acoustoelectric wave-propagation physics in single-crystal semiconductors to break the reciprocity of acoustic signal transmission. In this talk ultra-low-loss planar and fin nano-acoustic resonators, filters, isolators and circulators will be reviewed and benchmarked against their electronic, electromagnetic, photonic, and ferrite-based counterparts. Acoustic-waveguide geometry engineering techniques to suppress wave propagation dispersion over ultra-wide bands will be reviewed. The challenges with power-handling, linearity and interference in nano-acoustic nonreciprocal components will also be addressed and the effectiveness of doping-profile engineering techniques for compensation of elastic anharmonicities and suppression of nonlinear scattering will be discussed.