Compact Multiband Folded Loop Chip Antenna for Small-Size Mobile Phone

A multiband folded loop chip antenna with a very small volume of 1 cm3(40 times 5times 5 mm3) is presented. The antenna has a simple metal pattern comprising a folded loop strip and a tuning pad, and is especially suited for application in small-size mobile phones (groundplane length 60 mm only) for multiband operation. The metal pattern is attached on the surfaces of a foam base, and the first three resonant loop modes (0.5-, 1.0-, and 1.5-wavelength modes) of the antenna can be excited with good impedance matching by simply adjusting proper dimensions of the tuning pad and its location along the folded loop strip. The excited 0.5-wavelength mode forms as the antenna's lower band at about 900 MHz for GSM operation, while the 1.0- and 1.5-wavelength modes are formed into a wide operating band at about 1900 MHz for the antenna's upper band to cover DCS/PCS/UMTS operation. Design considerations of the proposed folded loop chip antenna are described, and effects of the tuning pad on controlling the performances of the antenna are shown.