Calculation of Transient Radiation Fields from Axial Symmetric Sources
Proper understanding of the results of acoustic imaging, tissue characterization, and tomography utilizing pulsed ultrasound requires inclusion of the diffraction effects of the pulsed wave. A method is presented for the efficient calculation of pulsed ultrasonic waves from an axially symmetric source mounted in a rigid baffle and excited with an arbitrary time excitation. The technique uses a spatial modal analysis based on a series expansion of the source velocity term in either of two sets of basis functions. The choice of basis functions is arbitrary. The expansion is equivalent to a decomposition of the excitation into a set of propagation modes. Each mode is then simply propagated by the technique with rapid convergence of the solution that requires evaluation of approximately thirty (or less) terms of a series, allowing rapid computer-based solutions of the field at an object plane or at a receiver plane. Several numerical solutions are given.
KeywordsSpatial Frequency Observation Plane Lower Order Mode Naval Postgraduate School Source Velocity
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