Tunable impedance matching networks and tunable diplexer matching systems are provided. A tunable impedance matching network can include an impedance element connected between first and second nodes for communicating signals between the first and second nodes. For example, the impedance element can be a transmission line or an inductor. Further, the matching network can include a first capacitor connected in parallel with the impedance element, wherein the first capacitor is tunable. The matching network can also include a second capacitor comprising first and second terminals. The first terminal of the second capacitor can be connected to the first node. The second terminal of the second capacitor can be connected to a local voltage reference for the first node. A third capacitor comprises first and second terminals. The first terminal of the second capacitor can be connected to the second node. The second and third capacitors can also be tunable.