Spurious coupling between length-weighted transducers acoustically connected by means of a multistrip coupler

It is shown experimentally that, between two length-weighted transducers separated from each other by directional coupler, relatively strong direct coupling may be produced by acoustic surface waves that are radiated under an angle with the normal to the transducers. A mechanical barrier reduces this direct coupling substantially. A device is most susceptible to undesirable coupling of this nature if the two transducers have identical structures.