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There are numerous engineering design problems where the use of wires to transfer power and communicate data thru the walls of a structure is prohibitive or significantly difficult that it may require a complex design. Such systems may be concerned with the leakage of chemicals or gasses, loss of pressure or vacuum, as well as difficulties in providing adequate thermal or electrical insulation. Moreover, feeding wires thru a wall of a structure reduces the strength of the structure and makes the structure susceptibility to cracking due to fatigue that can result from cyclic loading. Two areas have already been identified to require a wireless alternative capability and they include (a) the container of the Mars Sample Return Mission will need the use of wireless sensors to sense pressure leak and to avoid potential contamination; and (b) the Navy is seeking the capability to communicate with the crew or the instrumentation inside marine structures without the use of wires that will weaken the structure. The idea of using elastic or acoustic waves to transfer power was suggested recently by Y. Hu, et al.1. However, the disclosed model was developed directly from the wave equation and the linear equations of piezoelectricity. This model restricted by an inability to incorporate head and tail mass and account for loss in all the mechanisms. In addition there is no mechanism for connecting the model to actual power processing circuitry (diode bridge, capacitors, rectifiers etc.). An alternative approach which is to be presented is a network equivalent circuit that can easily be modified to account for additional acoustic elements and connected directly to other networks or circuits. All the possible loss mechanisms of the disclosed solution can be accounted for and introduced into the model. The circuit model allows for both power and data transmission in the forward and reverse directions through acoustic signals at the harmonic and higher order resonances. This system allows or the avoidance of cabling or wiring. The technology is applicable to the transfer of power for actuation, sensing and other tasks inside sealed containers and vacuum/pressure vessels.
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