Wave impedance - encyclopedia article about Wave impedance.

The wave impedance of an electromagnetic wave, is the ratio of the transverse components of the electric and magnetic fields (the transverse components being those at right-angles to the direction of propagation). For a transverse-electric-magnetic (TEM) plane wave travelling through a homogeneous medium, the wave impedance is everywhere equal to the intrinsic impedance of the medium. In particular, for a plane wave travelling through empty space, the wave impedance is equal to the impedance of free space. The symbol Z is used to represent it and it is expressed in units of ohms. The symbol η (eta) may be used instead of Z for wave impedance to avoid confusion with electrical impedance, although η is also the symbol for electromagnetic impedance, the light wave equivalent of wave impedance.

The wave impedance is given by

$\text{[math]}$

In terms of the parameters of an electromagnetic wave and the medium it travels through, the wave impedance is given by

$\text{[math]}$

where μ is the magnetic permeability, ε is the electric permittivity and σ is the conductivity of the material the wave is travelling through. In the equation, j is the imaginary unit, and ω is the angular frequency of the wave. In the case of a dielectric (where conductivity is zero), the equation reduces to

$\text{[math]}$

Wave impedance of free space

In free space, $\text{[math]}$ H/m and $\text{[math]}$ F/m. So, the value of wave impedance in free space is

$\text{[math]}$

In a perfect dielectric, the wave impedance can be found by dividing Z₀ into the refractive index. In anything else, the formula becomes larger and a complex number is the result.

Wave impedance in an unbounded dielectric

In a perfect dielectric, $\text{[math]}$ H/m and $\text{[math]}$ F/m. So, the value of wave impedance in a perfect dielectric is

$\text{[math]}$

In a perfect dielectric, the wave impedance can be found by dividing Z₀ into the refractive index. In anything else, the formula becomes larger and a complex number is the result.

Wave impedance in a waveguide

For any waveguide in the form of a hollow metal tube, (such as rectangular guide, circular guide, or double-ridge guide), the wave impedance of a travelling wave is dependent on the frequency $\text{[math]}$ , but is the same throughout the guide. For transverse electric (TE) modes of propagation the wave impedance is

$\text{[math]}$

where f_c is the cut-off frequency of the mode and for (TM) modes

$\text{[math]}$

For a waveguide or transmission line containing more than one type of dielectric medium (such as microstrip), the wave impedance will in general vary over the cross-section of the line.

References

This article contains material from the Federal Standard 1037C (in support of MIL-STD-188), which, as a work of the United States Government, is in the public domain.

Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. These components oscillate at right angles to each other and to the direction of propagation, and are in phase with each other.
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electric field. This electric field exerts a force on other electrically charged objects. The concept of electric field was introduced by Michael Faraday.

The electric field is a vector field with SI units of newtons per coulomb (N C⁻¹
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magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. Magnetic fields surround electric currents, magnetic dipoles, and changing electric fields.
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A transverse mode of a beam of electromagnetic radiation is a particular intensity pattern of radiation measured in a plane perpendicular (i.e. transverse) to the propagation direction of the beam.
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plane wave (also spelled planewave) is a constant-frequency wave whose wavefronts (surfaces of constant phase) are infinite parallel planes of constant amplitude normal to the phase velocity vector.
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An optical medium is material through which electromagnetic waves propagate. It is a form of transmission medium. The permittivity and permeability of the medium define how electromagnetic waves propagate in it.
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In problems of electromagnetic wave propagation in a transmission medium, the electromagnetic impedance, also known as the intrinsic impedance, is defined as the ratio of the electric to magnetic field amplitudes:

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For the physical constant, see .

Impedance of Free Space (also known as ) is a Canadian IDM and electronica group.

External links

Sonic Union has some archives of material.

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OHMS can refer to:

The plural of ohm, a unit of resistance, named after Georg Ohm.
O.H.M.S. On His/Her Majesty's Service.

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Euskadi Ta Askatasuna or ETA (Basque for "Basque Homeland and Freedom"; IPA pronunciation: [ˈɛːta]) is an armed Basque nationalist organisation.
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Electrical impedance, or simply impedance, describes a measure of opposition to a sinusoidal alternating current (AC). Electrical impedance extends the concept of resistance to AC circuits, describing not only the relative magnitudes of the voltage and current, but also the
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Light is electromagnetic radiation of a wavelength that is visible to the eye (visible light). In a scientific context, the word "light" is sometimes used to refer to the entire electromagnetic spectrum.
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In electromagnetism, permeability is the degree of magnetization of a material that responds linearly to an applied magnetic field. Magnetic permeability is represented by the Greek letter μ. The term was coined in September, 1885 by Oliver Heaviside.
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Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium, and is determined by the ability of a material to polarize in response to the field, and thereby reduce the total electric field inside the material.
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Electrical conductivity or specific conductivity is a measure of a material's ability to conduct an electric current. When an electrical potential difference is placed across a conductor, its movable charges flow, giving rise to an electric current.
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In mathematics, the imaginary unit (or sometimes the Latin or the Greek iota, see below) allows the real number system to be extended to the complex number system . Its precise definition is dependent upon the particular method of extension.
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angular frequency ω (also referred to by the terms angular speed, radial frequency, and radian frequency) is a scalar measure of rotation rate. Angular frequency is the magnitude of the vector quantity angular velocity.
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A dielectric is a physical model commonly used to describe how an electric field behaves inside a material. It is characterised by how an electric field interacts with an atom. It is possible to approach dielectrics from either a classical interpretation or a quantum one.
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In physics, free space is a concept of electromagnetic theory, corresponding to a theoretical "perfect vacuum".

Definition

Free space simply means that there is no material or other physical phenomenon
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The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. For example, typical glass has a refractive index of 1.
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waveguide may refer to any linear structure that guides electromagnetic waves. However, the original and most common meaning is a hollow metal pipe used for this purpose.

A dielectric waveguide employs a solid dielectric rod rather than a hollow pipe.
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Microstrip is a type of electrical transmission line which can be fabricated using printed circuit board [PCB] technology, and is used to convey microwave-frequency signals.
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Federal Standard 1037C, entitled Telecommunications: Glossary of Telecommunication Terms is a United States Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended.
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