Super-High-Frequency Band Filters Configured with Air-Gap-Type Thin-Film Bulk Acoustic Resonators

Abstract

We investigate under what conditions a uniform quench of a superfluid atomic Fermi gas leads to the emergence of spatial inhomogeneities. We demonstrate that, if the system is larger than the coherence length, the superfluid order parameter becomes spatially nonuniform. Spatial modulations develop through a parametric excitations of pairing modes with opposite momenta. Their growth is eventually suppressed by nonlinear effects resulting in a state characterized by a random superposition of wave packets of the superfluid order parameter. This state can be probed by measuring the molecular momentum distribution following a fast sweep to the BEC side of the Feshbach resonance.

Toward Ka Band Acoustics: Lithium Niobate Asymmetrical Mode Piezoelectric MEMS Resonators

“…The state-of-the-art acoustic resonators beyond 24 GHz resort to either the fundamental FBAR mode in a 100 nm thin AlN film or an overtone FBAR mode in a thicker AlN film [3] [4]. In either case, significant performance compromise has to be made in the process of scaling, which might lead to inadequate performance for 5G applications.…”

Electromechanical coupling and gigahertz elastic properties of ScAlN films near phase boundary

“…AlN film bulk acoustic wave (BAW) resonator filters are promising for application for mobile communication applications that operate at over 5 GHz. 1,2 The low electromechanical coupling of AlN films which determines the bandwidth of the filter is a drawback, although they do offer Q factor. 3 The large bandwidth of Sc doped AlN resonators has therefore received increasing interest in recent years.…”

Low-thickness high-quality aluminum nitride films for super high frequency solidly mounted resonators

“…operate in the ultra high frequency range at frequencies between 800 MHz and 2200 MHz. The extremely rapid expansion of the mobile phone market is boosting the development of new communication systems addressing the super high frequency (SHF) range, to prevent radio wave congestion or interference and allow the efficient use of the frequency spectrum [1][2][3], High frequency filters are fundamental components of wireless communications systems. Filters based on bulk acoustic wave (BAW) resonators have been extensively developed during the last ten years and have become the best choice for very high frequency filtering applications [4].…”

“…SHF applications require a remarkable reduction of the thickness of the AIN films to values for which their crystal quality and piezoelectric activity drop significantly [9], owing to the poor crystal quality of the material in the initial stages of growth. BAW resonators based on ultra thin AIN films (from 150 nm to 300 nm) are being developed in some research institutions and companies [1][2][3][10][11][12][13][14]. However, the crystal quality of such films is still far from that of thicker films.…”

“…This, along with the increase of the acoustic losses with frequency, explains why high frequency resonators exhibiting simultaneously great values of the effective electromechanical coupling coefficient (k| ff ) and quality factor (Q_) are hardly achieved, particularly in the case of SMRs [11,12]. So far, competitive high frequency resonators with k^f f greater than 6% have only been achieved in devices suspended over an air cavity [1][2][3], In this work we investigate the growth of very thin AIN films on iridium (Ir) electrodes by a special alternating current (AC) reactive sputtering process that controls the interaction between the energetic particles of the glow discharge with both the Al target and the substrate during the deposition process. The aim is to achieve films exhibiting good crystal quality from the very first stages of growth.…”