Bandwidth enhancement of coupled‐fed on‐board printed PIFA using bypass radiating strip for eight‐band LTE/WWAN slim mobile phone

By connecting a bypass radiating strip to the radiating portion of a coupled-fed on-board printed PIFA (planar inverted-F antenna), significant bandwidth enhancement can be obtained.The bypass radiating strip provides a bypass for the excited surface currents of the printed PIFA, which leads to more uniform surface current distributions on the printed PIFA. This behavior can result in slow variations in the antenna's input impedance over the operating bands, which makes it very promising to achieve improved impedance matching; thus, enhanced bandwidths of the printed PIFA are obtained. In this study, with a small footprint to be printed on the no-ground portion of 15 × 48 mm2 in the system circuit board of the mobile phone, the proposed on-board printed antenna is especially suitable for slim mobile phone applications and can generate two wide operating bands to respectively cover the LTE700/GSM850/900 operation (698–960 MHz) and the GSM1800/1900/UMTS/LTE2300/2500 operation (1710–2690 MHz). The proposed antenna held by the user's hand and attached to the user's head is also tested for its SAR values over the eight operating bands. Measured and simulated results are presented. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2059–2065, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.25406