What is a Branchline Coupler?

A Branch Line Coupler is the simplest type of a Quadrature Coupler or 90° Hybrid Coupler. This device is basically a 3 dB, four port directional coupler with 90° phase difference between its output ports. It can be used as a single antenna Transmitter/Receiver system or an I/Q signal splitter/combiner.

90 Degree Hybrid Coupler Schematic