50 GHz Piezoelectric Acoustic Filter

TL;DR

This paper demonstrates a novel 50 GHz piezoelectric acoustic filter using multilayer LiNbO3 technology, achieving the highest frequency to date and promising for future wireless communication applications.

Contribution

It introduces a new multilayer stack design enabling high-frequency acoustic filters up to 50 GHz, surpassing previous frequency limits in piezoelectric filter technology.

Findings

Achieved 50 GHz filter frequency, the highest reported to date.

Demonstrated a compact filter with 3.3 dB IL and 2.9% FBW.

Used multilayer P3F LiNbO3 stack enabling high-order mode operation.

Abstract

This paper presents significant frequency scaling of acoustic filter technology to 50 GHz. This achievement is enabled by the P3F LiNbO3 multilayer stack, in which piezoelectric thin-films of alternating orientations are transferred in sequence, thereby allowing efficient exploitation of high-order modes with high quality factor (Q) and coupling coefficient (k2) in a thicker piezoelectric stack. The demonstrated filter is comprised of twelfth-order symmetric (S12) mode lateral-field-excited bulk acoustic wave resonators (XBARs), built on a 4-layer periodically poled piezoelectric (P3F) 128 Y-cut lithium niobate (LiNbO3) stack. The filter exhibits 3.3 dB insertion loss (IL) and a fractional bandwidth (FBW) of 2.9%. The miniature design, with a footprint of 0.36 mm2, makes it promising for future wireless front-end applications. These results represent the highest frequency acoustic filters reported to date, setting a new benchmark in piezoelectric filter technology. Upon further development, the platform could enable filters further into the FR2 range, essential for next-generation communication systems.