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    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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Gap between the stripline trace and ground trace - RF Cafe Forums

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Sujatha Gopinath
Post subject: Gap between the stripline trace and ground trace
Unread postPosted: Thu Jan 20, 2005 6:31 am

I understand from the replies that I got for my posting on 14th of Jan that the rule of thumb that I am following on the gap between the microstrip trace and ground trace is acceptable. For reference, I am repeating below the lines I had posted.

[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? ]

Now, I would like to know if the above rule of thumb holds good for stripline as well. Have in mind that the width of stripline is almost five times lesser compared to microstripline for given substrate and charecteristic impedance. For 50 ohms line impedance and Rogers RO4003C, trace width for microstrip is 44 mils and for stripline it is around 9 mils.


Post subject: Rule of thumb
Unread postPosted: Fri Jan 21, 2005 9:05 am

You can save yourself a lot of time and aggrevation by going on the microwave office website and downloading their "free" transmission line calculator.


Post subject: Re: Gap between the stripline trace and ground trace
Unread postPosted: Fri Jul 01, 2005 11:31 am

The rules of thumb I use for RO4003 is to use a dielectric constant of 3.6 when calculating coplanar waveguide etc. and use APPCad (Free) from Agilent.
I have produced boards with runs up to 18"long, going through blind vias that are "flat" to about 10GHz and -3db at 14GHz. Also for coplarnar wave guide, you must take into account ground planes and core thickness. Get the program and don't putz around with rules of thumb with 4003 there really are none except for the adjustment of the constant,(which came from a Rogers Application Engineer).


Post subject:
Unread postPosted: Fri Jul 01, 2005 1:05 pm
Site Admin
User avatar

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
This is what that programs are made up for, to provide you with the exact dimensions of the transmission lines and required gaps. Use these tools and you will save yourself an unneccessary spin of PCB layout.

Good luck!

Best regards,

- IR

Posted  11/12/2012
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