Radial Mode Lithium Niobate Rosen Transformer

TL;DR

This paper presents a novel lithium niobate radial-mode Rosen transformer with high transformation ratio and efficiency, demonstrating its potential as a high-performance, passive voltage amplifier platform without magnetic components.

Contribution

First implementation of a two-port radial-mode Rosen transformer on lithium niobate with high transformation ratio and detailed modeling for efficient power conversion.

Findings

Achieved a transformation ratio of 16 and high electromechanical coupling of 16.8%.

Demonstrated an open-circuit voltage gain of over 45.

Developed an accurate equivalent circuit model fitting both simulated and measured data.

Abstract

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.