An electromagnetic coupler includes a first transmission line connecting an input port to an output port and a second transmission line adjacent the first transmission line and connecting a coupled port to 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 electromagnetically coupled to at least one of the first and second transmission lines. An adjustable impedance is coupled between the tuning element and a reference node. Varying resistive impedance components causes an adjustment to the coupling factor and reactive impedance components provide frequency filtering effects.