arXiv subjects

Eric Stolt

Publications and source records attributed to Eric Stolt.

5 recordsLinked to original sources

arXiv2026

Spurious-Free Lithium Niobate Bulk Acoustic Wave Resonator with Grounded-Ring Electrode

High-performance piezoelectric resonators are promising energy storage elements for piezoelectric power conversion due to their compact footprint and low loss at frequencies where conventional magnetic components become bulky and inefficient. However, their practical use is often limited by the trade-off between a high electromechanical coupling coefficient (k^2) for wide-band operation and the emergence of spurious acoustic modes that limit the resonators' inductive bandwidth. This work reports a spurious-free thickness-extensional (TE)-mode bulk acoustic wave (BAW) resonator in single-crystal lithium niobate (LN) based on a grounded-ring electrode architecture. The proposed structure is analyzed through simulation and experimentally validated using electrical characterization and laser Doppler vibrometry (LDV). The results show that the grounded ring modifies the effective boundary conditions of the acoustic device, enabling a piston-like modal response that suppresses lateral spurious modes across the inductive band. The demonstrated device operates at 10.14 MHz and achieves an electromechanical coupling coefficient of 29.6%, a maximum in-band Bode quality factor (Q_Bode) of 5230, and a figure of merit (FoM, Q*k^2) of 1548. These results establish the grounded-ring TE-mode LN BAW resonator as a practical platform for piezoelectric power conversion and a broader design approach for realizing high-performance spurious-free acoustic resonators.

eess.SY↗

arXiv2025

Radial Mode Lithium Niobate Rosen Transformer

In this work, we demonstrate the first two-port radial-mode Rosen transformer based on 36$^{\circ}$Y-cut lithium niobate (LN) for piezoelectric power conversion. The device achieves a high transformation ratio (TF) of 16, a high electromechanical coupling factor ($k^2$) of 16.8\% and a quality factor ($Q$) of 2500, yielding an outstanding figure of merit (FoM = $Q \cdot k^2$) of 420. The fabricated transformer features a large effective turns ratio of 16 and delivers an open-circuit voltage gain of 45.56 (unloaded) and 40.57 with a load of 1 M$\Omega$ in parallel with 0.1 pF, validating its ability to provide efficient passive voltage amplification. An equivalent circuit model was developed to accurately fit both finite-element-simulated and measured admittance spectra, enabling reliable parameter extraction. These results establish LN radial-mode resonators as a promising high-performance, magnetic-less transformer platform.

physics.app-ph↗

arXiv2025

Periodically Poled Piezoelectric Lithium Niobate Resonator for Piezoelectric Power Conversion

As the demand for compact and efficient power conversion systems increases, piezoelectric power converters have gained attention for their ability to replace bulky magnetic inductors with acoustic resonators, enabling higher power density and improved efficiency. Achieving optimal converter performance requires resonators with high quality factor ($Q$), strong electromechanical coupling ($k^2$), high power handling capability, and a spurious-free response. Lithium niobate (LN) has emerged as a promising material in this context due to its high figure of merit (FoM = $Q \cdot k^2$). While previous studies on single-layer LN resonators have demonstrated high FoM values, they typically operate at relatively low resonance frequencies ($f_s$). Recently, periodically poled piezoelectric film (P3F) structures, formed by stacking piezoelectric layers with alternating crystal orientations, have shown the potential to both scale up the operating frequency and enhance the FoM compared to single-layer counterparts in piezoelectric power conversion. This work presents the first P3F thickness-extensional (TE) LN resonator for power conversion, operating at 19.23 MHz, with a large \textit{$k^2$} of 29\% and a high \textit{Q} of 3187, achieving a state-of-the-art (\textit{ $f_s \cdot Q$}) product among piezoelectric power resonators. A high-power testing procedure is performed to systematically study the nonlinear behavior and power handling of P3F LN for power applications. With further optimization, P3F TE resonators have the potential to open up a new design space for high-power and high-frequency power conversion.

physics.app-ph↗

arXiv2025

Lithium Tantalate Bulk Acoustic Resonator For Piezoelectric Power Conversion

We present the first lithium tantalate (LT) thickness-extensional (TE) mode bulk acoustic resonators designed for piezoelectric power conversion, showcasing a low temperature coefficient of frequency (TCF) of -13.56 ppm/K. These resonators also exhibit high quality factors (Q) of 1698, and electromechanical coupling coefficients ($k^2$) of 8.8%, making them suitable for efficient power conversion applications. A grounded ring structure is leveraged for spurious mode-free response and figure of merit (FoM=$k^2 \times Q$) enhancement near the series resonance. The temperature dependency of Q and $k^2$ is experimentally tested over a wide temperature range, from $25^{\circ}\text{C}$ to $130^{\circ}\text{C}$, demonstrating the resonators thermal stability and consistent performance under varying conditions. This work highlights the potential of LT resonators in the future development of thermally stable power electronic systems, enabling more reliable and efficient piezoelectric power converters.

physics.app-ph↗

arXiv2023

Spurious-Free Lithium Niobate Bulk Acoustic Resonator for Piezoelectric Power Conversion

Recently, piezoelectric power conversion has shown great benefits from replacing the bulky and lossy magnetic inductor in a traditional power converter with a piezoelectric resonator due to its compact size and low loss. However, the converter performance is ultimately limited by existing resonator designs, specifically by moderate quality factor (Q), moderate electromechanical coupling (kt2), and spurious modes near resonance. This work reports a spurious-free lithium niobate (LiNbO3) thickness-extensional mode bulk acoustic resonator design, demonstrating Q of 4000 and kt2 of 30% with a fractional suppressed region of 62%. We first propose a novel grounded ring structure for spurious-free resonator design, then validate its performance experimentally. Upon further work, this design could be extended to applications requiring spurious suppression, such as filters, tunable oscillators, transformers, etc.

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