0 db coupler

i need to implement a 4x4 butler matrix using microstrip and to avoid line crossover (overlap), i would like to use a 0 dB coupler, but can't find any article describing how to design it. can you please help me?

thanks in advance :)

A 3-branch coupler with all lines 50 Ohm will give you a 0 dB coupler and you can use it as a crossover junction.