Academy of EMC

 

The underlying physics

In a homogeneous, lossless medium, the velocity v [m/sec] of an electromagnetic wave is v=c/√(εr·μr), where c is the speed of light in vacuum (299 792 458 m/s), εr is the relative permittivity and μr the relative permeability of the lossless medium.
Wavelength and frequency are linked by λ=v/f. With εr=μr=1 the relation reduces to the familiar free-space form λ=c/f. Increasing either material parameter slows the wave and shortens the wavelength accordingly.

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• Wavelength λ [m] of a sinusoidal signal is given by its frequency f [Hz] and the velocity of the electromagnetic wave v [m/sec]: λ=v/f.

• Velocity v [m/sec] is given by the permittivity ε=ε0·εr and the permeability μ=μ0·μr of the medium through which the electromagnetic wave travels: v = 1/√(ε0·εr·μ0·μr) = c/√(εr·μr).

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Typical applications in EMC and RF engineering

RF and microwave designers apply wavelength estimates throughout the design and test process: sizing antennas and field probes, identifying resonant cable and enclosure dimensions, evaluating near-field versus far-field boundaries, selecting measurement distances in semi-anechoic chambers, and judging when a structure becomes electrically large. RF and microwave designers apply the same relation when laying out microstrip lines, striplines, and waveguides — substituting the effective permittivity of the substrate yields the guided wavelength used for impedance matching, stub design, and resonator dimensioning.

 

Assumptions and limits

The calculator assumes a linear, isotropic, non-dispersive, lossless medium. For materials with significant loss tangent, frequency-dependent εr or μr, or anisotropic behaviour — and for transmission-line geometries whose effective permittivity differs from the bulk substrate value — a full-wave or transmission-line model is required.

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