Bulk acoustic wave transformer based on the combination of the high-ε epitaxial PbTiO3 and low-ε ScAlN thin films

A rectifier antenna (called a rectenna) is useful for wireless power charging of electronic devices. To enhance the rectifier efficiency, we propose sub-GHz bulk acoustic wave (BAW) piezoelectric transformers based on the combination of high and low dielectric constant (epsilon) thin films. The input layers are sputter-epitaxial lead titanate (PbTiO3) films, which possess both high electromechanical coupling coefficient k(t) and high epsilon, and the output layers are ScAlN films with high k(t) but low epsilon. The voltage gain of 12.3 in 50MHz ranges and 40.9 in 400MHz ranges was experimentally observed in the thickness-extensional mode BAW transformer. The experimental results are in good agreement with the theoretical predictions of the electromechanical transmission line model. The BAW transformer is promising for a high voltage gain transformer for wireless power transfer.

Automated summary

This study proposes sub-GHz bulk acoustic wave (BAW) piezoelectric transformers based on a combination of high and low dielectric constant thin films, which can enhance the efficiency and voltage gain of rectifier antennas. Experimental results demonstrate the potential application of this BAW transformer in wireless power transfer.