Artificial generation of a directional phase-encoded wavefield

An acoustic transmitter having a phase-varying wavefield is constructed. The phase function indicates the direction of transmission using only single source and receiver. Such a source is constructed by combining two piezo films with directional beam patterns, each of which is driven by a similar wide-band signal having a distinct phase function. Superposition of the two wavefields results in phase variation with direction and the underlying theory is discussed. Experiments demonstrate that such phase-varying wavefield is achievable, and reflections obtained from a plane rigid surface in air indicate that the reflected phase function is as predicted by simple theory.