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What's the permeability value of dielectric material?

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micro_tech

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Hi,

Dielectric material that's been used in microstrip antenna, one of it's important parameter is the permittivity (dielectric constant), ε.
How about it's permeability, µ? Is this value is nothing to care of...
Because usually it didn't mention about it.
I wonder actually for dielectric material how much is the permeability value?

Thanks in advance
 

radiohead

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Re: Dielectric Material

The dielectric has no magnetic properties, you can safely assume that the relative µ is 1 or µ=µ0.
 

jallem

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Dielectric Material

Most of the material are dielectric or conductors
in nature. For example plastics, wood, paper, etc.
They do not have magnetic properties. That is the
reason.
 

rrumpf

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Re: Dielectric Material

Yes, most materials used in RF and antennas do not have a significant magnetic response, or permeability. It should also be mentioned that if you ever chose a material that did have a magnetic response, it becomes just as important as the dielectric response. In some regards it is more important to consider because these properties tend to be more temperature sensitive and frequency dependent than dielectric materials.

-Tip
 

micro_tech

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Re: Dielectric Material

jallem said:
Most of the material are dielectric or conductors
in nature. For example plastics, wood, paper, etc.
They do not have magnetic properties. That is the
reason.

I've also have read form some reference (sorry I've forgot) that all materials can be classified in terms of their magnetic behaviour,
and it could be falling into one of five categories depending on their bulk magnetic susceptibility.
That categories are:
- diamagnetic
- paramagnetic
- ferromagnetic
- ferrimagnetic
- antiferromagnetic

so dielectric that been used in microstrip antenna is in general can be considered to which category?
 

rrumpf

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Re: Dielectric Material

All diamagnetic materials (e.g. silver, copper, lead, water) magnetize so as to oppose an applied magnetic field. This gives them a permeability a little less than free space permeability. All other magnetic materials (para, ferro, antiferro, and ferri) become magnetized to add with the applied magnetic field. For this reason, they tend have permeability greater than free space. Para and antiferro tend to have very small permeability, while ferro and ferri can have very high permeability.

I suppose any dielectric must ultimately be magnetic in one of these ways, but the response is so weak, it is easily ignored. You should just consider these "nonmagnetic" and set µr=1.0.

-Tip
 

micro_tech

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Re: Dielectric Material

rrumpf said:
All diamagnetic materials (e.g. silver, copper, lead, water) magnetize so as to oppose an applied magnetic field. This gives them a permeability a little less than free space permeability. All other magnetic materials (para, ferro, antiferro, and ferri) become magnetized to add with the applied magnetic field. For this reason, they tend have permeability greater than free space. Para and antiferro tend to have very small permeability, while ferro and ferri can have very high permeability.

I suppose any dielectric must ultimately be magnetic in one of these ways, but the response is so weak, it is easily ignored. You should just consider these "nonmagnetic" and set µr=1.0.

-Tip
Hi rrumpf,

Thanx for the reply and explanation...
so in other words, dielectric materials could be one of diamagnetic, paramagnetic or antiferromagnetic type...?
with the µr≈1
 

rrumpf

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Re: Dielectric Material

I suppose we are running into symantics, but setting µr=1 should be a very good approximation for your model.

-Tip
 

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