Reflection of Microwave Pulses From Acoustic Waves: Summary of Experimental and Computational Studies
NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
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In 1, 4, the authors proposed and analyzed an interrogation inverse problem methodology based on use of an acoustic wave as a reflecting virtual interface for propagating impulses. It is by now well accepted e.g., see 2, 7, 11, 14 that acoustic pressure waves will interact with electromagnetic signals in ways that often mimic interfacial partial reflectionpartial transmission for the electromagnetic waves. The response of atomic electrons to an applied electrical field in a material medium results in a material polarization with a concomitant index of refraction that is a function of the local density in the material. Thus, material density fluctuations produced by a sound wave induce perturbations in the index of refraction. Previous computational work in 1, 3 suggested that it might be possible to detect reflections of microwave frequency EM waves from a slowly relative to the speed of the EM wave moving acoustic wave front. These efforts are focused on reflections in a Debye medium. The authors made an argument for a simple pressure dependent dielectric model in which the Debye parameters exhibit a linear acoustic pressure dependence. In 1, finite-element simulations for a simple 1D geometry demonstrated computationally that EM reflections from the acoustic pulse are possible. These findings were confirmed with 2D computations in 3. The results of 1, 3 consisting of a theoretical framework as well as computational validation of such an approach provide ample motivation for significant proof-of-concept experimental investigations of the proposed methodology. These prompted our preliminary experiment on which we report here to look for microwave frequency EM reflections from an acoustic pulse.
- Numerical Mathematics
- Radiofrequency Wave Propagation