any specification about space of microstrip in high freq?

In GaAs MMIC technology, is there any technological experience about the space of microstrip?at 5.4GHz,8GHz, what is the strict limit of the space? is it OK that twice of the microstrip width of the space? if this will be effect the circuit performance, i must be change my project , plz give some advices !
thanks for all!

purian

Do not understand what you mean by "space" of the microstrip? Do you mean the length of a line? Do you mean the gap distance between two different lines?

yes, the space is the distance between two microstrip lines.

For microstrip, the SPACING needs to be at least 1.5 times greater than the width of the lines.

I can suggest you a simple trick I've used, easy and free of charge.

Use a software called TX-line (download it from AWR, it is free).
This tool has different line model to synthesize and/or analize transmission lines.
You have just to put your microstrip parameters in the first tab to check electrical parameters, such as impedance and so on. Using the same phisical parameters in the Couples MS Line, you can play with Gap until you'll see that the impedance is not affected any more. This means that the coupling between the two lines is negligible.

I hope it can help.

Mazz

thanks for sharing, i got the idea,i want to know that is there great differences between the simulated and measured results?
also, is the difference of impendence with 0.5Ohm a great influence?

purian
please remember that this is just a trick that gives you an approximate idea of which value to use.
There will always be a certain coupling, and the distance depends on your isolation spec (20dB or 100dB, for example).
If I was in your shoes, I'll take some more margin, and if you need more accuracy, use a proper simulator, such as Agilent Momentum.
Mazz