GHz Low-Loss Acoustic RF Couplers in Lithium Niobate Thin Film

We present the first group of GHz low-loss acoustic radio frequency (RF) couplers using the fundamental symmetric (S0) mode in X-cut lithium niobate thin films. The demonstrated multistrip couplers (MSCs) significantly surpass the insertion loss (IL) and the operating frequency of the previous works...

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Bibliographic Details
Published in:IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2020-07, Vol.67 (7), p.1448-1461
Main Authors: Lu, Ruochen, Yang, Yansong, Li, Ming-Huang, Gong, Songbin
Format: Article
Language:English
Subjects:
Acoustic delay line (ADL)
Acoustic waves
Acoustics
Bandwidths
Broadband
Couplers
Coupling
Couplings
directional coupler
Insertion loss
Lithium niobate
Lithium niobates
microelectromechanical systems
multistrip coupler (MSC)
piezoelectricity
Radio frequency
S0 mode
Signal processing
Strips
Thin films
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Summary:We present the first group of GHz low-loss acoustic radio frequency (RF) couplers using the fundamental symmetric (S0) mode in X-cut lithium niobate thin films. The demonstrated multistrip couplers (MSCs) significantly surpass the insertion loss (IL) and the operating frequency of the previous works in more compact structures, thanks to the large electromechanical coupling and low loss of S0 in lithium niobate. The design space of S0 MSCs is first explored. Devices with different coupling factors are fabricated using different numbers of strips. Based on the S0 testbed with an IL of 4.5 dB at 1 GHz, the hybrid coupler shows an IL of 7.5 dB, while the track changer shows an IL of 5.1 dB, over a 3-dB fractional bandwidth of 8%. Couplers at different frequencies (between 0.75 and 1.55 GHz) are also investigated. Upon further optimizations, the S0 MSC platform can potentially enable low-loss wideband signal processing functions toward an RF acoustic component kit.
ISSN:0885-3010
1525-8955
DOI:10.1109/TUFFC.2020.2971196