Ultra-wideband loop antenna coupled-fed by a monopole feed for penta-band folder-type mobile phone

An ultra-wideband coupled-fed loop atttelnml for penta-band operation in the folder-type mobile phone is presented. The antenna comprises a loop strip curd a monopole feed: the latter not only serves as a coupling feed jar file loop strip to generate a 0.5-wavelength loop resonant mode, hot also provides a 0.25-wavelength monopole resonant mode for enhancing the operating bandwidth of the antenna. Hence, with an occupied volume of 2.6 cm(-3) only, the antenna cent provide a very wide operating band of larger than 100% err about 1.7 GHz (from 790 to 2450 MHz), allowing the antenna to cover GSM850/900/DCS/PCS/UMTS penta-band operation with radiation efficiencies larger than 70% for the folder-type mobile phone in the open state (talk condition). For the antenna in the close state (idle condition), it can still provide a very wide operating band just by including a matching circuit of a series chip capacitor tit the antenna's feeding point, and the radiation efficiencies over the five operating bands are still better than 5; h. Details of the proposed antenna are studied. (C) 2008 Wiley Periodical, Inc.