US Patent 7218186 Directional coupler

A directional coupler for low frequencies that is small and can handle high power levels. The directional coupler includes a pair of circuit lines having an input port, an output port, a forward coupled port and a reverse coupled port. The circuit lines are located proximate to each other such that they are electromagnetically coupled. A low pass filter is connected to the forward coupled port. The low pass filter shifts the operating frequency of the directional coupler.