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This paper reports on the demonstration of wideband spurious-free radio frequency micromechanical systems filters based on one-port shear horizontal (SH0) mode lithium niobate (LiNbO3) laterally vibrating resonators (LVRs). The fabricated filter has been demonstrated with an unprecedented spectral range of spurious-free response (290% of the center frequency), a low insertion loss of 2.1 dB, an excellent 30-dB shape factor of 1.48, and a 3-dB fractional bandwidth of 8.9%. The spurious free response is achieved by optimizing the building blocks of the filters, namely the LVRs, and employing a spurious mitigation design based on arraying single resonators with only two electrodes. The low loss and excellent shape factor are enabled by the demonstrated high electromechanical coupling ( \mathit kt^{2}=16.1 %), high quality factor ( Q =1093 ), and high figure of merit (FoM = 154) of the fabricated resonator arrays. [2016-0250] [ABSTRACT FROM PUBLISHER]

This work reports a comparative study of acoustic loss between different Lamb waves at GHz in thin-film lithium niobate (LiNbO3). The propagation loss (PL) of higher-order Lamb waves in thin-film LiNbO3 is studied for the first time using acoustic delay line (ADL) testbeds. The acoustic wave attenuation and quality factors ($Q$) of different Lamb waves are extracted, showing higher $Q\text{s}$ for higher-order Lamb modes than fundamental modes in air and vacuum at room temperature. The extracted $Q\text{s}$ are higher than those reported in thin-film LiNbO3 resonators, implying the electrode and anchor-induced loss as the dominant loss factors. The ADL-based loss analysis framework is readily extendable to acoustic damping study in other microwave acoustic platforms. [2021-0165] [ABSTRACT FROM AUTHOR]

This work reports an experimental study of acoustic loss in thin-film lithium niobate (LiNbO3) using acoustic delay lines (ADLs). Unlike prior resonator-based quality factor (Q) studies, this approach directly extracts the damping in thin-film LiNbO3, avoiding the influence of other intricate loss mechanisms, e.g., anchor loss and electrode-induced loss. Acoustic attenuation of fundamental symmetric (S0) and shear horizontal (SH0) waves are studied in suspended LiNbO3 thin films of different thicknesses. The attenuation is significantly higher in thinner LiNbO3 films, suggesting the LiNbO3 crystal degradation during the microfabrication as the primary loss origin. Nevertheless, the extracted equivalent Q in thin-film LiNbO3 is still higher than reported values, suggesting that anchor design and electrode quality remain the bottlenecks for higher Q. The proposed loss extraction framework is readily extendable to other acoustic thin-film structures. [2021-0107] [ABSTRACT FROM AUTHOR]

This article presents the design approach and the first demonstration of a wideband hybrid monolithic acoustic filter in the K-band, which exceeds the limitation of electromechanical coupling on the fractional bandwidth (FBW) of acoustic filters. The hybrid filter utilizes the codesign of electromagnetic (EM) and acoustic to attain wide bandwidth while keeping the advantages of small sizes and high Q in the acoustic domain. The performance trade space and design flow of the hybrid filter are also presented in this article, which allows this technology to be applied for filters with different center frequencies and FBWs. The hybrid filter is simulated by hybridizing the EM and acoustic finite element analysis, which are carried out separately and combined at a system level. The fabricated filter built with resonators having an electromechanical coupling of 0.7% based on the seventh-order antisymmetric Lamb wave mode (A7) has a 3-dB FBW of 2.4% at 19 GHz and a compact footprint of 1.4 mm2. [ABSTRACT FROM AUTHOR]

This paper reports on the analysis and removal of transverse spurious modes in shear horizontal (SH0) mode lithium niobate (LiNbO3) laterally vibrating resonators (LVRs). A length-controlled electrode configuration that employs an optimized overlapping length between the adjacent electrodes has been developed to subdue the spurious modes. The technique modifies the stress and electric field distribution in the resonator body, consequently enabling near zero electromechanical coupling ( kt^{2} ) for the higher order transverse spurious modes. The length-controlled electrode configuration also reduces the loss at the interface between the metal electrodes and the piezoelectric layer, demonstrating a more than 2\times enhancement in quality factors {Q} . The fabricated LiNbO3 LVR with the length-controlled electrode configuration has shown an unprecedented spectral range (100–200 MHz) of spurious-free response, a high \mathit {k}_{t}^{2}$ value of 20.1%, a {Q} value of 1150, and, thereby, a remarkably high figure of merit of 230. [ABSTRACT FROM AUTHOR]

This work presents an improved design that exploits dispersion matching to suppress the spurious modes in the lithium niobate first-order antisymmetric (A1) Lamb wave mode resonators. The dispersion matching in this work is achieved by micro-machining the lithium niobate thin film to balance the electrical and mechanical loadings of electrodes. In this article, the dispersion matchings of the A1 mode in lithium niobate based on different metals are analytically modeled and validated with finite-element analysis. The fabricated devices exhibit spurious-free responses with a quality factor of 692 and an electromechanical coupling coefficient of 28%. The demonstrated method herein could overcome a significant hurdle that is currently impeding the commercialization of A1 devices. [ABSTRACT FROM AUTHOR]