how to realize 209ohm microstrip ?

and can handle 20W Power
and can work from DC to 13.5GHz

I think it will be difficult... I have tried simulate it using some software and the line gets extremly thin. Is it becuase of matching you'll like to have that specific resistance? If so i would investigate the possibilyty of using some matching networks.

20 watts is not that bad. You need thick metalization on the top surface, a narrow line, and a very thick substrate. Figure our how thick you can make it without moding, and make it just a little thinner than that.

Hi,

be carefull, ANY discontinuity you might create with that line, intentionally or unintentionally can cause brake down (steps, bends, Tees etc.), calculations for power handling are valid for uniform lines only, standing waves have minima and maxima that can be critical. I used to work with that range of power (but larger than your case, 100W) and have regulary a fire to put down because the N connector to microstrip transition was hard to match perfectly. The problem was solved with replacing microstrip with stripline. Just to let you know, my microstrip was 50 Ohm so the problem was much easier to solve. Furthermore, microstrip of such high Zo is not recommanded due to high conductor loss, so even the power discipation on uniform line can be a problem)

Hope this helps, didn't mean to frighten you.

flyhigh

In my opinion you may start to think on some other solutions of your problem. Unfortunately it seems to be very unprobable to realize a stable 209 ohm in ustrip, and to handle such (relatively) high power.
g579

You should use a thick substraight with low Dialectric This should make your
traces fatter thus letting you have a realistic (width) 209Ohm trace.
Look on the "Rogers" website, they have good selection, info and a "line calc"
tool. I think it's called "MWIJ"

Cheers

Thanks all above.
In fact I want to realize a highpass filter,which is so-called 'optimum distributed highpass filter' detailed in the sixth chapter of Jia-sheng Hong's book "microstrip filters for RF microwave application.'
the filter spec is :the fco=2.7GHz,and 55dBc@2.25GHz,and high cutoff Frequency is about 13.5GHz. The filter is constructed with a 50ohm main line and several parrallel short-circuited microstrip line with different characteristic impedances. I use Genetic Algorithm to optimise the filter and the result shows that some parallel short-circuited lines have characteristic impedance more than 200ohm.so the difficulty happen.

Oh. If it is a narrowband filter, use a quarter wave transformer to transform from 50 ohms to, say, 20 ohms. Then design your filter, which will now only need a 84 ohm transmission line (instead of 209). After the filter, transform back up to 50 ohms.