A varactor-based tunable matching network for a non-resonant mobile terminal antenna

In this paper, we present a varactor-based tunable matching network for a mobile terminal antenna based on a non-resonant capacitive coupling element. The system is able to enhance the power transfer to the antenna in the commonly used mobile communication bands within the frequency range 0.69 ≤ f [GHz] ≤ 3.6. The impedance of a mobile terminal antenna is dependent on the operating frequency and on the effects of the user interaction (e.g. hand and head proximity). This mismatched impedance can be correctly tuned using the proposed tunable matching network. In almost all of the typical usage scenarios, the transducer gain with the threshold value G_T = -1.25 dB can be achieved. The average value of the total efficiency of the fabricated mock-up-system in free space within the conventional bands is η = 68%. The good radiation performance with user interaction is also shown in this paper using the proposed matching network.