Re: branchline coupler
Hi,
sorry bibijons, I didn'i uderstand if you have succeed in optimizing coupler or not? 200deg is a big discrepancy, it might indicate that your lines dimensions are not all equal and you got rat race instead of branch coupler.
Unfortunately I don't have any experience with multisection couplers, but think that this could be the solution for widening the band of operation.
I don't think that can achieve exact phase shift of 90 deg at multiple frequencies. It is almost allways like 90 on one frequency only and then less then 90deg for lower (or higher) frequency and more than 90deg for higher (lower). The correct specification is +/- delta phase in a bandwidth. Anyway, bandwidth for the phase of 90 deg is not that bad, the limiting factor to determine the operating bandwidth of a hybrid is almost always the isolation between the ports (S12, S34 in your case). Reasonable values of isolation are regarded to be -25 to -30dB. Isolation bandwidth is 10-15% for single coupler secton.
flyhigh