Fields and Waves

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# Lale T. Ergene - PowerPoint PPT Presentation

Fields and Waves. Lesson 5.3. PLANE WAVE PROPAGATION Lossy Media. Wave Equations for a Conducting Medium. Homogenous wave equation for . Homogenous wave equation for . ; propagation constant is complex. Propagation Constant. Phase constant. Attenuation constant. [Np/m].

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Fields and Waves

Lesson 5.3

PLANE WAVE PROPAGATION

Lossy Media

Lale T. Ergene

Wave Equations for a Conducting Medium

Homogenous wave equation for

Homogenous wave equation for

; propagation constant is complex

Propagation Constant

Phase constant

Attenuation constant

[Np/m]

(for a lossy medium)

Solution of the Wave Equation

The Electric Field in phasor form (only x component)

General solution of the differential equation for a lossy medium

backward traveling in -z direction

forward traveling in +z direction

Intrinsic Impedance, ηc

The relationship between electric and magnetic field phasors is the same but the intrinsic impedance of lossy medium, ηc is different

If +z is the direction of the propagation

intrinsic impedance

Skin Depth, δs

shows how well an electromagnetic wave can penetrate into a conducting medium

Skin Depth

[m]

Perfect dielectric:

σ=0 α=0 δs=∞

Perfect Conductor:

σ=∞ α=∞ δs=0

Low-Loss Dielectric

defined when ε’’/ε’<<1

practically if ε’’/ε’<10-2, the medium can be considered as a low-loss dielectric

[Np/m]

[Ω]

Good Conductor

defined when ε’’/ε’>>1

practically if ε’’/ε’>100 , the medium can be considered as a good conductor

[Np/m]

[Ω]

• When 10-2≤ ε’’/ε’ ≤100, the medium is considered as a “Quasi-Conductor”.
• Do Problem 1

Average Power Density

Average power density

[W/m2]

Average Power Density

If ηc is written in polar form

Average power density

[W/m2]

where

Do Problem 2