Surface-Acoustic-Wave Waveguides for Radio Frequency Signal Processing

The large velocity of electromagnetic waves makes the design of waveguide structures such as couplers and delay lines at radio frequencies (RFs) prohibitively large for chip-scale implementation. In contrast, acoustic waves have velocities that are many orders of magnitude smaller. Thus, with the use of acoustic waves, RF waveguides become possible. In this article, the waveguiding of sub-1-GHz surface acoustic waves (SAWs) on 128° Y-cut lithium niobate (LiNbO3) is examined with demonstrations of straight waveguides, waveguide bends, and coupled waveguides. Furthermore, an electroacoustic variable phase shifter based on an SAW waveguide on a bonded 128° Y-cut LiNbO3 on silicon is demonstrated. Finally, an all-acoustic bidirectional RF phased array front end is demonstrated. The structures shown in this work can be implemented in commercial SAW foundries resulting in low-cost compact realizations of SAW microwave signal processing structures.