Antenna tuners or active antennas may improve the overall system performance significantly. Typically, antenna tuners are used in size-limited devices to widen antenna bandwidth.
An antenna tuner can be used as an impedance tuner in the antenna input or as a part of a resonator to tune the antenna’s resonant frequency. In both cases, the antenna tuner must be designed together with the antenna. Otherwise, the tuner’s benefit may become minimal or even counteractive.