Small‐size WWAN tablet computer antenna with distributed and lumped parallel resonant circuits

The technique of embedding a distributed parallel resonant circuit (PRC) and a lumped PRC, respectively, to enhance the bandwidths of the lower and upper bands of a small-size tablet computer antenna to cover the WWAN operation in the 824–960 and 1710–2170 MHz bands is presented. With the proposed technique, the antenna occupies a small volume of 40 × 10 × 3.8 mm3 only and can mainly be disposed on a thin FR4 substrate of 40 × 10 mm2. The antenna comprises a feeding portion, a long shorted strip, and an antenna ground. The shorted strip is short-circuited to the antenna ground, which is then connected to the display ground in the tablet computer. A lumped PRC and a distributed PRC are added at the front and open ends of the feeding portion, respectively. The two PRCs, respectively, generate a parallel resonance at the high-frequency tails of the first two resonant modes at about 900 and 1800 MHz contributed by the shorted strip to result in additional resonances occurred near the two resonant modes, thereby resulting in additional resonant modes excited in the desired antenna's lower and upper bands. This behavior greatly increases the operating bandwidths of the antenna's lower and upper bands, without additional resonant elements needed. Hence, small size for the proposed WWAN antenna is obtained. Details of the proposed antenna and the bandwidth enhancement techniques applied therein are presented. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1348–1353, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26811