An electromagnetic coupler includes a first transmission line connecting an input port to an output port. A second transmission line adjacent the first transmission line connects a coupled port and an isolation port. The electromagnetic coupler provides a coupled signal at the coupled port, which is representative of an input signal at the input port. The amplitude of the coupled signal is related to the amplitude of the input signal by a coupling factor. A tuning element is provided adjacent to the first or second transmission line and is coupled to an impedance. Varying impedance values cause an adjustment to the coupling factor and reactive impedance values provide frequency filtering effects.