FM couplers

The 3 dB couplers can be used as power-splitters or as power combiners and their most common application is as componentsin the design of combiners.They consist of two identical parallel transmission lines coupled over a length equal or approximately equal to l/4 and mounted in a common exterior conductor.The couplers are designed to achieve coupling differences in the operating frequency range at the output ports. The phase-shift between the two outputs is always 90