Low Support-Loss Miniaturized Rosen Transformer on 128 ° Y-Cut Lithium Niobate

This work presents a novel miniaturized Rosen transformer fabricated on a $128^{\circ} \mathrm{Y}$-cut lithium niobate wafer. In this design, optimized tethers and acoustic reflectors are carved out of the substrate, enabling a compact implementation of the Rosen transformer with superior quality factor and voltage gain. Measured results from the first-generation device exhibit a quality factor (Q) of approximately 4,700 in air with a measured voltage gain of $\sim 50$. Simulations based on the extracted electrical model indicate a peak efficiency of 70% for a $126 \mathrm{k} \Omega$ load, an open-circuit voltage gain of 84, and a figure of merit of~130.