Multi-Layers High Directivity Couplers

The presented high directivity narrowband multi-layers couplers consist of two transmission lines coupled beetween diffrent layers of PCB board. The main lines are coupled only at two points. The coupling value can be set from 3 dB to 30 dB. The couplers can be realized in different multilayer stack-ups thus can be easily integrated into PCB circuits. The directivity of the couplers is better than 30 dB in the narrow relative bandwidth of 2 %. The matching is better than 25 dB.