microstrip coupled line

why the length of microstrip coupled line resonator is λ/4 only?
plz give reason if anybody knows about it.....
any reply wil b appreciated...

Because....its not. The resonator is a little shorter than half wave.

It could be λ/4 or λ/2.

can u plz explain in detail?
im not getting ur ans.....

In theory it should be λ/4, but if u will try to do smaller it will work, but coupling will be hard to do less than 20dB...