Modeling Microwave Propagation in Natural Caves Passages

We introduce a direct, linear sampling approach to imaging in an acoustic waveguide with sound hard walls. The waveguide terminates at one end and has unknown geometry due to compactly supported wall deformations. The goal of imaging is to determine these deformations and to identify localized scatterers in the waveguide, using a remote array of sensors that emits time harmonic probing waves and records the echoes. We present a theoretical analysis of the imaging approach and illustrate its performance with numerical simulations.

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“…Proofs of Lemmas 2.2-2. 4. We analyze first in Section A.1 the forward problem (2.8)- (2.11) for the scattered wave field.…”

Section: ) Then It Has the Mode Expansionmentioning

confidence: 99%

“…Introduction and formulation of the problem. Sensor array imaging in waveguides has applications in underwater acoustics [34,3], nondestructive evaluation of slender structures [16,27], imaging of and in tunnels [29,21,4], etc. It is a particular inverse wave scattering problem that has been studied extensively for waveguides with known and simple geometry.…”

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confidence: 99%

A direct approach to imaging in a waveguide with perturbed geometry

Borcea

Cakoni

Meng

2019

Journal of Computational Physics

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“…In most cases, as we walk along the walkway through the caves we will see that a variety of stalactites, stalagmites, and other cave formations evolve and develop over time. The variable conditions of caves particularly from the geometric configuration perspective make any theoretical and numerical studies of radio wave propagation in caves difficult, leaving only the empirical approach as the most feasible way for conducting propagation prediction in caves [4][5][6]. Nevertheless, this trend has seen a slight change of late as other methods have also been used to study the cave environment.…”

Section: Introductionmentioning

confidence: 99%

Propagation Measurements and Modelling of Natural Tropical Caves

Soo¹,

Lim²,

Rafie³

et al. 2022

PIER M

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Caves are a vital environment with an understudied propagation characteristic to date. In this paper, we investigate the propagation environments of three tourist caves in Malaysia at 900 MHz, 2.4 and 5.8 GHz. Path loss exponents are derived from measurement data for line-of-sight (LoS) and non-line-of-sight (NLoS) sections for vertical-vertical (VV) and horizontal-horizontal (HH) polarizations. Channel fading effects are subsequently analyzed. Beyond the conventional method of computing the path loss exponent values, machine learning is also incorporated into the processing of data for yielding optimum results. The findings of this work lay a good foundation towards a greater understanding of the propagation scenarios in natural tourist caves, and they help towards establishing reliable wireless communications inside such environments.

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“…Introduction. Guided waves have applications in electromagnetics [9], optics and communications [22,27], imaging underwater [19,5,14,15], imaging of and in tunnels [3] and so on. The classical theory of guided waves is for ideal waveguides with perfectly reflecting straight walls and filled with homogeneous media, where the wave equation can be solved using separation of variables.…”

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Wave Propagation in Randomly Perturbed Weakly Coupled Waveguides

Borcea¹,

Garnier²

2020

Multiscale Model. Simul.

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We present an analysis of wave propagation in a two step-index, parallel waveguide system. The goal is to quantify the effect of scattering at randomly perturbed interfaces between the guiding layers of high index of refraction and the host medium. The analysis is based on the expansion of the solution of the wave equation in a complete set of guided, radiation and evanescent modes with amplitudes that are random fields, due to scattering. We obtain a detailed characterization of these amplitudes and thus quantify the transfer of power between the two waveguides in terms of their separation distance. The results show that, no matter how small the fluctuations of the interfaces are, they have significant effect at sufficiently large distance of propagation, which manifests in two ways: The first effect is well known and consists of power leakage from the guided modes to the radiation ones. The second effect consists of blurring of the periodic transfer of power between the waveguides and the eventual equipartition of power. Its quantification is the main practical result of the paper.

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Modeling Microwave Propagation in Natural Caves Passages

Cited by 19 publications

References 28 publications

A direct approach to imaging in a waveguide with perturbed geometry

A direct approach to imaging in a waveguide with perturbed geometry

Propagation Measurements and Modelling of Natural Tropical Caves

Wave Propagation in Randomly Perturbed Weakly Coupled Waveguides

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