Acoustic surface wave loss mechanisms on Bi12GeO20 at microwave frequencies

Abstract

Measurements of the acoustic surface wave propagation loss in vacuum on both 001‐cut and 111‐cut 110‐propagating Bi12GeO20 have been made between 200 and 2000 MHz. Approximate f‐squared frequency dependence was obtained with a value at 1 GHz of 1.45 dB/μsec. Temperature‐dependencemeasurements illustrate the loss peaks in the vicinity of 50–100 K which are characteristic of Bi12GeO20. The difference in loss between 298 and 4.2 K agrees with over‐all room‐temperature data indicating attenuation is inherent to the crystal itself and not due to imperfections. Air loading contributes an additional loss of 0.19 dB/μsec at 1 GHz. Beam steering and diffraction considerations illustrate the superiority of the 001 cut over the 111 cut. For linear operation at 320 MHz, surface wave devices on 001‐cut 110‐propagating Bi12GeO20 should be limited to power densities of 9 mW/mm.