TY - JOUR

T1 - Permittivity Gradient Induced Depolarization

T2 - Electromagnetic Propagation with the Maxwell Vector Wave Equation

AU - Shaffer, Stephen

AU - Mahalov, Alex

N1 - Funding Information:
This work was supported by the Air Force Office of Scientific Research under Grant FA9550-19-1-0064.
Publisher Copyright:
© 1963-2012 IEEE.

PY - 2021/3

Y1 - 2021/3

N2 - Recent interest in 3-D vectorial sensors requires the development of vectorial propagation methods, rather than scalar wave equation approaches. We derive a vector wave equation from Maxwell's equations for a medium which has an inhomogeneous dielectric permittivity dominated by variation along one dimension. It is well known that the electric field components decouple for homogeneous media. However, 1-D permittivity variations yield an upper triangular system of scalar wave equations with the wave polarization component parallel to the inhomogeneous direction/axis acting as a forcing term for the orthogonal components. The main implication is that waves with polarization oriented parallel to the permittivity gradient will act as a forcing term and excite other polarization components and, thus, induce depolarization. Contemporary studies treat the permittivity as a constant when deriving a wave equation or paraxial approximation, and then re-introduce via inhomogeneous wave speed, variable permittivity, thus missing important terms and physical mechanisms in their resulting equations. Contemporary studies neglect the term in the Maxwell vector wave equation responsible for this effect. Application of the electromagnetic propagation depolarization effect is demonstrated numerically for an air-sea interface evaporation duct with a 500 MHz source.

AB - Recent interest in 3-D vectorial sensors requires the development of vectorial propagation methods, rather than scalar wave equation approaches. We derive a vector wave equation from Maxwell's equations for a medium which has an inhomogeneous dielectric permittivity dominated by variation along one dimension. It is well known that the electric field components decouple for homogeneous media. However, 1-D permittivity variations yield an upper triangular system of scalar wave equations with the wave polarization component parallel to the inhomogeneous direction/axis acting as a forcing term for the orthogonal components. The main implication is that waves with polarization oriented parallel to the permittivity gradient will act as a forcing term and excite other polarization components and, thus, induce depolarization. Contemporary studies treat the permittivity as a constant when deriving a wave equation or paraxial approximation, and then re-introduce via inhomogeneous wave speed, variable permittivity, thus missing important terms and physical mechanisms in their resulting equations. Contemporary studies neglect the term in the Maxwell vector wave equation responsible for this effect. Application of the electromagnetic propagation depolarization effect is demonstrated numerically for an air-sea interface evaporation duct with a 500 MHz source.

KW - Electromagnetic (EM) propagation

KW - nonhomogeneous media

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U2 - 10.1109/TAP.2020.3016463

DO - 10.1109/TAP.2020.3016463

M3 - Article

AN - SCOPUS:85102262371

SN - 0018-926X

VL - 69

SP - 1553

EP - 1559

JO - IEEE Transactions on Antennas and Propagation

JF - IEEE Transactions on Antennas and Propagation

IS - 3

M1 - 9171553

ER -