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This work studies the influence of substrate loss on the performance of acoustic resonators and on-chip inductors and investigates the effective substrate resistivity of seven commonly used substrates in silicon-based devices. The substrates include X-cut lithium niobate (LiNbO3) film with two different thicknesses (400 nm and 1.6 $\mu \text{m}$) on high-resistivity Si (HR-Si) and amorphous Si wafers, SiO2 film with two different thicknesses on HR-Si, and bare HR-Si. The effective resistivities of these substrates are extracted using coplanar waveguides (CPWs) over a frequency range from 1 to 40 GHz. Using the effective resistivity approach, the efficiency of two substrate loss reduction techniques—Si wafer removal and amorphous Si—in reducing substrate loss is quantified. Comparison of the extracted substrate resistivities of the suspended and un-suspended dielectric-on-Si structures and comparison of LiNbO3 on HR-Si and amorphous Si are carried out. Substrate loss reduction techniques are more advantageous for a thinner dielectric film and at a lower frequency range due to the higher filling factor of the electric field in the Si wafer. Finally, by comparison of the effective substrate resistivity of SiO2 film on an HR-Si with bare HR-Si, thick plasma-enhanced chemical vapor deposition (PECVD) SiO2 film is found to be a good insulation layer to reduce substrate loss. [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]

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 work presents a class of micro-electro-mechanical system (MEMS)-driven radio frequency filters in the X-band. The X-band center frequencies are achieved by resorting to the third-order antisymmetric Lamb wave mode (A3) in a 650-nm-thick Z-cut lithium niobate thin film. A novel bandwidth (BW) widening technique based on using the self-inductance of the top interdigital transducers and bus lines is proposed to overcome the limitations set by the electromechanical coupling (${k} _{t}^{2}$) and satisfy the demands in miniaturization and wide BW. Four different designs of the filters are designed and fabricated to show the trade-off among BW, insertions loss (IL), out-of-band rejections, and footprint. Due to the spurious-free and high- ${Q}$ performance of the A3 lithium niobate resonators, the fabricated A3 lithium niobate filters have demonstrated small in-band ripples and sharp roll-offs. One of these fabricated has demonstrated a 3-dB BW of 190 MHz, an IL of 1.5 dB, and a compact footprint of 0.56 mm2. Another design is fabricated to demonstrate a 3-dB BW of 170 MHz, an IL of 2.5 dB, an out-of-band rejection of 28 dB, and a compact footprint of 1 mm2. [ABSTRACT FROM AUTHOR]

This work presents a new class of microelectromechanical system (MEMS) resonator toward 60 GHz for the fifth-generation (5G) wireless communications. The wide range of the operating frequencies is achieved by resorting to different orders of the antisymmetric Lamb wave modes in a 400-nm-thick Z-cut lithium niobate thin film. The resonance of 55 GHz demonstrated in this work marks the highest operating frequency for piezoelectric electromechanical devices. The fabricated device shows an extracted mechanical $Q$ of 340 and an $f\times Q$ product of $1.87\times 10^{13}$ in a footprint of $2 \times 10^{-3}$ mm2. The performance has shown the strong potential of LiNbO3 antisymmetric mode devices for front-end applications in 5G high-band. [ABSTRACT FROM AUTHOR]

This paper presents a new class of micro-electro-mechanical system (MEMS) C-band filters for 5G front-ends. The filter is comprised of resonators based on the first-order asymmetric Lamb wave (A1) mode in thin-film lithium niobate. Two filters have been demonstrated at 4.5 GHz with sharp roll-off, flat in-band group delay, and spurious-free response over a wide frequency range. The first design shows a 3-dB fractional bandwidth (FBW) of 10%, an insertion loss (IL) of 1.7 dB, an out-of-band (OoB) rejection of −13 dB, and a compact footprint of 0.36 mm2, while the second design shows a 3-dB FBW of 8.5%, an IL of 2.7 dB, an OoB rejection of −25 dB, and a footprint of 0.9 mm2. The demonstrations herein mark the largest FBW achieved for acoustic-only filters at 5G frequencies. [2019-0083] [ABSTRACT FROM AUTHOR]