A Loop Antenna with Coupling Strip and Tuner for All-Metal-Shell Handset Application

A dual-band frame antenna with coupling strip and tuner is proposed in this work for all-metal-shell mobile telephone application with all the metal devices being considered The metal-shell handsets are getting more and more popular nowadays due to the robustness and its fascinating appearance. The metal-shell associated with surrounding electronic components would occupy the metal clearance, which will absorb the energy radiated by the antenna. This work provides an optional solution to design the antenna with all the metal components like front-and-back facing cameras, telephone receiver and steel sheet taken into consideration, where the metal shell of the handset and a coupling strip are utilized as part of the antenna. The metal shell of the handset has a symmetric C-shaped gap with a width of 2mm and no other breakpoints to decrease the robustness of the structure. The proposed antenna is able to generate radiation covering the bandwidth of 824-960 MHz (GSM) and 1710-2690 MHz (DCS/PCS/UMTS/L TE) for mobile communication. With the application of the tuner, the antenna can get a broadband characteristic and the coupling strip may add the capacitance of the structure, making the antenna resonate at the lower band as 0.25λ resonant mode and as 0.5λ resonant mode at the higher band. The principle of the tuner has also been discussed in the paper, helping locate the proper situation to induce the switchable inductor. A prototype has been fabricated to verify the radiation performance in a practical handset test environment.