Stepped Broadside Directional Coupler

I need to do a 6-18GHz directional coupler and decided to do a broadside coupler. Eagleware tells me that I have ~2.5dB of ripple with a single stage 1/4wave coupler and therefore need to do a 2-stage. Does someone have an example of doing a 2-stage broadside directional coupler?

Thanks

Added after 1 hours 48 minutes:

Is the spacing between stages a chebyshev function or something else?