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Microstrip Line Structure with No Ground Plane

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kmmaran1979

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Hi All,

I am looking for any equation for Microstrip Line structure with no ground plane. Its difficult to find? Can anyone help who have experience in this type of structure.

Actuall I need to calculate length of strips with no ground plane.

Brgds
Manimaran
 

RF currents must return to its source...It's a fundamental law..
This return can be either by ground plane or another proper way.Therfore if there isn't ground plane underneath of MS line, there should be ground plane just besides of the line called as "Coplanar Waveguide" without ground.
 
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    bepsml

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@kmmaran1979: what do you want to do?

You can excite a single wire (or single strip) transmission line with respect to a local ground (Gobau or G-line). However this isn't used for transmisson over short distance. (w.r.t. wavelength). A transmission line without return circuit close below or around the strip (PCB trace) will act as an antenna (for example a quarter wave whip fed over a ground plane).
 

Hey Guys,

Thanks for the reply guys....

I want to design microstrip antenna with no ground plane, and to calculate the length of the strips, I need a Effective Permittivity equation. The equation normally described is with the ground plane, so mine is a different case. Does anyone know about Suspended Microstrip, any idea one that.

Brgds
Manimaran
 

Hello,

I don't have a simple formula for that. When the substrate thickness << lambda, the reduction in propagation speed will be in the percent range as most of the reactive E-field energy is in air instead of the dielectric. Small traces with thick substrate result in higher effective permittivity (so more reduction in propagation speed). This is because a larger part of integral E*dle is in the dielectric.
 

The best in your case is to use an EM simulator and see how you can deal with a suspended strip feeder over a dielectric.
I'm pretty sure, in this situation the strip it will radiate almost the same as your antenna.
 

i am working for this case [lanar without ground plane structure, any advice for my design
 

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