Couplers are used for power division into multiple output ports. Generally, these are designed without crossovers. Directional  couplers does not require crossovers. But, the couplers used in power amplifier design may use crossovers. 

In the multilayer PCB design, crossovers are implemented using via holes between two layers. 

Yes, sir you are right, But what is the meaning of crossover (Is it crossing via  the line), If you can give some references to diagrams or in detail its concept it will be helpful

HELLO

crossovers are very common in buttler matrix design, you can build a crossover by cascading two hybrid couplers

thanks