here is another idea so called "de Ronde strip-slot coupler paper."
F.C. de Ronde. "A New Class of Microstrip Directional Couplers." 1970 G-MTT International
Microwave Symposium Digst of Technical Papers 70. 1 (1970 [MWSYM]): 184-189.
By using Cohn's slotline in combination with a microstrip. simple 90 as well as 180 directional
couplers of any coupling value can be made. As examples an ultra flat 10 db coupler for 1 - 12
GHz, an octave wide (2 - 4 GHz) magic tee and an almost lumped proximity coupler for 2 - 8
GHz (all on alumina substrate) have been made.