The effects of non-uniform loss on time reversal mirrors

Abstract

A time-reversal mirror in a solid circular waveguide using a single, time-reversal element ARLO 4, 31 (2003); 10.1121/1.1558377 The remote field effect: Models and interpretations AIP Conf. Proc. 497, 95 (1999); 10.1063/1.1301989Effect of suppressing of the photodeflection signal at opposed interaction of electromagnetic waves AIP Conf.Time reversal mirrors work perfectly only for lossless wave propagation; dissipation destroys time-reversal invariance and limits the performance of time-reversal mirrors. Here, a new measure of time-reversal mirror performance is introduced and the adverse effect of dissipation on this performance measure is investigated. The technique of exponential amplification is employed to partially overcome the effect of non-uniform loss distributions, and its success is tested quantitatively using the new performance measure. A numerical model of a star graph is employed to test the applicability of this technique on realizations with various random spatial distributions of loss. A subset of the numerical results are also verified by experimental results from an electromagnetic time-reversal mirror. The exponential amplification technique is a simple way to improve the performance of emerging technologies based on time-reversed wave propagation such as directed communication and wireless power transfer. C 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

Focusing waves at arbitrary locations in a ray-chaotic enclosure using time-reversed synthetic sonas

“…The above calculation does not include propagation loss. If we assume that the loss is uniform and results in an amplitude decay of e −t/τ with amplitude decay time τ , and also assume that τ is approximately frequency-independent, then we can apply an exponential window function to the synthetic sona to simulate the effect of propagation loss [37].…”

Spatio-temporal wavefront shaping in a microwave cavity

“…Examples of a complex medium at optical frequencies include highly scattering opaque ones as well as biological tissues or multimode fibers [3][4][5][6][7][8]; in the microwave domain, forests or cities can be considered multiple scattering media, while reverberating media are also very common, ranging from reverberation chambers for electromagnetic compatibility tests, via open disordered cavities for computational imaging to indoor environments trapping wireless communication signals [9][10][11][12]. Numerous techniques, notably time reversal and wave front shaping [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], have been proposed to take advantage of the multiple scattering and reveberation occuring during propagation. A common ground of these approaches is that they make use of the secondary sources offered by scatterers and reflectors, which provide additional degrees of freedom (DoF), to the point that they can even outperform focusing in homogeneous media [28][29][30][31][32].…”

Spatiotemporal Wave Front Shaping in a Microwave Cavity

“…Examples of a complex medium at optical frequencies include highly scattering opaque ones as well as biological tissues or multimode fibers [3][4][5][6][7][8]; in the microwave domain, forests or cities can be considered multiple scattering media, while reverberating media are also very common, ranging from reverberation chambers for electromagnetic compatibility tests, via open disordered cavities for computational imaging to indoor environments trapping wireless communication signals [9][10][11][12]. Numerous techniques, notably time reversal and wave front shaping [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], have been proposed to take advantage of the multiple scattering and reveberation occuring during propagation. A common ground of these approaches is that they make use of the secondary sources offered by scatterers and reflectors, which provide additional degrees of freedom (DoF), to the point that they can even outperform focusing in homogeneous media [28][29][30][31][32].…”