Seven‐band surface‐mount loop antenna with a capacitively coupled feed for mobile phone application

A surface‐mount loop antenna with a capacitively coupled feed capable of seven‐band operation in the mobile phone is presented. The capacitively coupled feed successfully excites the 0.5‐, 1.0‐, and 1.5‐wavelength modes of the loop antenna. Further, the presence of the capacitively coupled feed leads to a new loop path, whose length is slightly less than that of the original loop strip. The 0.5‐, 1.0‐, and 1.5‐wavelength modes of the new loop path are also excited with good impedance matching. The two 0.5‐wavelength modes of the new loop path and original loop strip form a wide bandwidth of 310 MHz for the antenna's lower band to cover GSM850/900 operation. The other modes of the two loops form a very wide bandwidth of larger than 1 GHz for the antenna's upper band to cover GSM1800/1900/UMTS/WLAN/WiMAX operation. With seven‐band operation achieved, the proposed loop antenna only occupies a small volume of 60 × 10 × 3 mm 3 (1.8 cm 3 ), and owing to its thin thickness of 3 mm only, and the antenna is very promising for thin mobile phone applications.