Small-size LTE/WWAN coupled-fed loop antenna with band-stop matching circuit for tablet computer

By combining the use of a coupling feed and a band-stop matching circuit, the proposed small-size loop antenna for the tablet computer application can operate at its quarter-wavelength mode as the lowest resonant mode and provide two wide operating bands (704960 and 17102690 MHz) to cover the eight-band LTE/WWAN operation (LTE700/GSM850/900 and GSM1800/1900/UMTS/LTE2300/2500 bands).The loop antenna comprises a T-shape radiating feed, a coupled shorted strip, an antenna ground, and a band-stop matching circuit on the antenna ground. The antenna's metal pattern includes a printed pattern on a thin FR4 substrate of planar size 10 x 55 mm2 and a metal strip of size 4 x 55 mm2 formed a part of the coupled shorted strip and connected orthogonally to the printed pattern. The antenna's occupied volume and the required length of 55 mm along the top edge of the display ground are both the smallest among the internal LTE/WWAN antenna for the tablet or laptop computers that have been reported for the present. Detailed operating principle of the proposed antenna including the effects of the coupling feed using the T-shape radiating feed and the band-stop matching circuit for bandwidth enhancement is discussed. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:11891193, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26765