Gap width for Grounded Coplanar Waveguide (Grounded CPW)

[VAURIEN]

coplanar waveguide

With a grounded coplanar waveguide, is there a minimum gap width?

The smaller you make the gap G, the smaller you can make the width of the transmission line W to get the same impedance. Now that I didn't work with grounded coplanar waveguides yet - is it ok to have a gap width of 0.25mm (10 mil) for a 1GHz system, or does this give me problems to have such a small gap?

(The losses will go up with smaller transmissions lines, ok - but are there other drawbacks)

 

[vfone]

coplanar waveguide grounded formula

You can use this thin gap if the PCB manufacturer can keep this high precision of the process.
One think that you must do is, the ground on each side of the trace shall be greater than 5 x (G+W+G).

 

[VAURIEN]

coplanar waveguide formula

You can use this thin gap if the PCB manufacturer can keep this high precision of the process.
One think that you must do is, the ground on each side of the trace shall be greater than 5 x (G+W+G).

Thanks alot for your help!

The width of the ground would have been my next question
Did you take this rule of thumb from a certain book or website (I've checked the whole library of the local university, not a single book contains some practial formulas like the one you gave), or is it a formula taken from your own experience?