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Gap Between the Microstip Trace and Ground Trace - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement

Sujatha Gopinath
Post subject: Gap between the Microstip trace and ground trace
Unread postPosted: Fri Jan 14, 2005 5:27 am

If 'W' is the width of the microstrip line, maintaining a gap of 'W' between the microstrip line and ground trace/plane next to it on the same layer is considered as good RF practice. Am I right on this thumb rule?

If anyone has opinion on this , pl let me know. Let me know even if you agree on it. I am following this thumb rule in the RF board I am making. It will greatly aid in coming out with good board with your valuable opinions.


Post subject: Microstrip Line width
Unread postPosted: Fri Jan 14, 2005 11:09 am

The rule of thumb is correct but remember it is a rule of thunb. The width is what determines the impedance of the line so I would recommend going on the Microsoft Office Website and downloading there "free" transmission line calculator. I am sure Kirt has a link to the sight. In this way you will know for a fact that you have the proper impedance. Keeping the ground trace a W away from the ground trace is usually adequate but I usually keep it 2W away.


Post subject:
Unread postPosted: Fri Jan 14, 2005 11:39 am

Yes it is a good practice. I did it in my latest board design and will be doing it in the next too.


Kirt Blattenberger
Post subject: Re: Microstrip Line width
Unread postPosted: Fri Jan 14, 2005 12:16 pm
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Joined: Sun Aug 03, 2003 2:02 pm
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Anonymous wrote:
...I would recommend going on the Microsoft Office Website and downloading there "free" transmission line calculator. I am sure Kirt has a link to the sight.

Right you are. There is a link to it (Tx-Line is the applet name) on the Software page (1) and the Calculators page (2), and the direct link to the MWO site is here (3). It is quite a nice program for free!

- Kirt Blattenberger :smt024


Post subject:
Unread postPosted: Mon Jan 17, 2005 3:55 am

Please make sure that GND away from the Transmission Line (At least 3 to 4 times of the width due to the GND coupling effects if it is filter / high power applications).

Or make use of Coplanar Waveguide with GND plane, which is very similar to the Microstrip but it has lots of advantages.

Please check Microstrip Vs Coplanar Waveguides (with GND plane)

Posted  11/12/2012

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