An Acoustic-electromagnetic Piezoelectric Waveguide Coupler

Theory and experiment are presented for a device which couples travelling waves in an electrical transmission line with flexural waves in an elastic beam. Coupling of the two wave types is achieved using a segmented piezoelectric layer adhered to the beam and connected to the transmission line. The key design parameter is the non-dimensional coupling length. A simple expression for calculating its magnitude is derived. For the design used, this length was predicted to be four wavelengths. Experiments yielded a similar value.