Quarter-wavelength printed loop antenna for GSM/DCS/PCS/UMTS operation

A folded printed loop antenna with small length (62 mm) and occupied area (< 100 mm²) and capable of GSM/DCS/PCS/UMTS operation in the mobile phone has been proposed. The loop antenna can operate at its 0.25lambda mode as the lower band for covering GSM operation, and its 0.5lambda and 1.0lambda modes can also be generated to form the upper band for covering DCS/PCS/UMTS operation. The successful excitation of the three resonant modes is obtained by incorporating a simple series LC matching circuit. With proper selection of the series capacitor and inductor (0.47 pF and 13 nH here) in the matching circuit, the large inductive reactance of the 0.25lambda mode of the loop antenna can be compensated, and good impedance matching over the 0.5lambda and 1.0lambda modes can also be achieved. Antenna gain for frequencies over the operating bands has also been shown.