Designing antenna booster cases for mobile phones using capacitive coupling techniques

Additional antenna elements are designed on the flip cover of the mobile phones to boost the radiation performance of the mobile antennas. We used the capacitive coupling technique and the multi-resonant technique to implement antenna booster cases. The designed prototypes show that the antenna booster can make the internal antennas to have the average radiation efficiencies over 50%, which is difficult to achieve because of interferences with the surrounding metal parts.