Embodiments of coupler systems (10) include a directional coupler (12), a tuning element (14a, 14b), and an actuator (16a, 16b). The coupler (12) is configured to split an input signal into two output signals or, alternatively, to combine two input signals into a single output. The tuning element (14a, 14b) is a capacitive device that allows the frequency response of the coupler (12) to be varied, so that the coupler (12) can be tuned to a particular frequency or range of frequencies at a given operating condition. The actuator (16a, 16b) generates a mechanical force that actuates tuning element (14a, 14b).