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[vijaireghunath]

I would like to know the relationship b/w permeability,permittivity and propagation constant..


When the propagation constant become imaginary how it reflects surface waves?

[bigSteve]

k = propagation constant

it is a measure of how quickly the waves alter in space

k = 2*pi/lambda = 2*3.14/wavelength

This means k is a function of frequency

wavelength = c/f/sqrt(eps*mu)=(speed of light)/frequency/sqrt(permeability*permittivity)

If you have an imaginary propagation constant, this means your waves are dying off (attenuating) as they travel. This means the medium has some conductivity.

This doesn't have anything to do with surface waves, which are waves that ride along a surface.

[vijaireghunath]

Thank you for u r reply , i am in need of some clarification

2*pi/lamda is phase constant....

lamda =1/f*sqrt(permittivity in freespace* permeability in free space)....

Propagation constant is a measure of amplitude change of the wave as it propagate in a given direction ..(gamma=alpha+i*beta)


Propagation constant is a combination of attenuation and phase constant ... When it imaginary means phase constant is not zero......

When we use negative permeability (positive permittivity) material how does the propagation constant become imaginary and when we use it in ground plane how it reflect surface waves.. ?

when pemeability become negative phase constant become imaginary then attenuation constant become real...

[bigSteve]

No, phase constant = 2*pi/lambda is not necessarily a real number

k = 2*pi/lambda = wavenumber = propagation constant = real in a lossless medium with positive eps and mu

k=2*pi*f*sqrt(mu*eps)

Note that with conductivity, epsilon can be imaginary, from ampere's law of maxwell's equations. This gives rise to propagation loss in lossy mediums such as salt water, glass, etc

If epsilon is negative, yes you will also have wave decay

Read up on this stuff in an electromagnetics text and it should become clear