US Patent 7907032 Directional coupler

A directional coupler includes a main line connected at a first end to an input port and at a second end to an output port, a coupled line connected at a first end to a coupled port and at a second end to an isolated port, and a phase shifter connected at a first end to the isolated port and at a second end to the coupled port. The phase shifter phase shifts a second reflected wave component such that the second reflected wave component is opposite in phase to a first reflected wave component, the second reflected wave component traveling from the output port to the coupled port through the isolated port and the phase shifter, the first reflected wave component traveling from the output port to the coupled port through the coupled line.