How to make equivalent micrstrip line instead of coupled line?

Hi,
I would like to know, how can I make equivalent microstrip line which will be behaving as a ideal coupled line. Thank you.

Depends on what you mean by "ideal". The only difference between a microstrip coupled line and something like slabline, is that the two modes have slightly different effective dielectric constants. Is that what you mean?

I have seen people overlay a small rectangle of dielectric over the gap, or make the gap region have a sawtooth-like shape, in order to try to compensate for the two different propogation velocities.

Actually,

I am asked to design a coupler with a ideal coupled transmission line instead of a ordinary microstrip line, where the behavior of the microstrip line & ideal coupled line will be same in phase & amplitude.