Metal Shell Effect on Multi-Mode Antennas for Wideband Mobile Applications

The metal shell is usually considered as a negative factor that degrades the impedance bandwidth of mobile terminal antennas. Here, we propose a different perspective on utilizing the metal shell to enhance the bandwidth. Through our study, beyond the antenna’s own modes, the cavity modes induced between the metal shell and the motherboard are also excited. By designing the antenna and the metal shell jointly, multiple cavity modes are controlled to enhance the bandwidth. As an example, a segmented half-loop antenna is designed in a tablet computer to demonstrate the positive effect of the metal shell on antenna’s bandwidth. The experimental results indicate that a −6-dB impedance bandwidth of 3.27−8.46 GHz is achieved with a compact antenna dimension of 0.28 × 0.047 × 0.011 λ_L ³, exhibiting the potentials for antenna designs in various metal-shell mobile terminals.