Simulating Echo Responses from Arbitrary-Geometry Targets Using Mode Conversion Approach

Abstract

A computational method based on the spatial impulse response and on the discrete representation computational concept is proposed for the determination of the echo responses from arbitrary-geometry targets. A major contribution of this paper is the development of an improved version of the method considering a mode conversion approach at the reflector surface. It is supposed that each point of the transducer aperture can be considered as a source radiating hemispherical wave to the reflector. The local interaction with each of the hemispherical waves at the reflector surface can be modeled as a plane wave impinging on a planar surface, using the respective reflection coefficient. The method is valid for all field regions and can be performed for any excitation waveform radiated from an arbitrary acoustic aperture. The effects of target geometry, position, and material on both the amplitude and shape of the echo response are studied. The model is compared to experimental results obtained using broadband transducers together with, for instance, plane and cylindrical concave rectangular reflectors (aluminum, brass and acrylic) in a water medium.