Abstract
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.
Highlights
A S THE sub-6-GHz spectrum becomes overcrowded with applications, the research community starts to explore beyond 6 GHz for new spectral venues to advance wireless capabilities
We develop a hybrid filter design that combines chip-scale reactive elements with A7 mode LiNbO3 resonators at 19 GHz
A design tradeoff analysis is performed onto the design space of such a wideband hybrid monolithic acoustic filter, which guides efficiently optimizing the filter performance and sets a realistic performance objective
Summary
A S THE sub-6-GHz spectrum becomes overcrowded with applications, the research community starts to explore beyond 6 GHz for new spectral venues to advance wireless capabilities. Several bands ranging from 12 to 27 GHz have been proposed [1], sharing the same challenge in scaling conventional front-end components well beyond their current operating frequencies. One indispensable front-end component that is difficult to scale in frequency is the acoustic filters that have been commercially successful for 4G [2], [3]. Frequency scaling without compromising performance remains difficult due to various technical bottlenecks in material integration, device fabrication, and filter design for acoustic filters. The scaling approaches so far can be classified into two categories. The first type resorts to the reduction in feature size for increasing the center frequency
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