Small-Size Stacked Inverted-F Antenna With Two Hybrid Shorting Strips for the LTE/WWAN Tablet Device

The stacked inverted-F antenna with two hybrid shorting strips placed close to the antenna's feeding strip can provide two wide operating bands to cover long-term evolution/wireless wide-area network operation (698-960/1710-2690 MHz) in the tablet device. The antenna's lower and higher bands are, respectively, contributed by the longer and shorter arms of the antenna. The two hybrid shorting strips include an inductive shorting strip (chip-inductor-loaded strip) and a capacitive shorting strip which capacitively couples to the antenna's shorter arm. The longer arm is also coupled through a chip inductor to the feeding strip such that the longer arm has a decreased resonant length for the low-band operation and, on the other hand, has very small effects on the high-band operation, which is mainly contributed by the shorter arm. The feeding strip is also embedded with a chip capacitor such that an internal high-pass matching circuit formed by the inductive shorting strip and the capacitive feeding strip is obtained to greatly widen the antenna's low-band bandwidth, with small effects on the high-band operation. On the other hand, the capacitive shorting strip is added to greatly enhance the bandwidth of the antenna's higher band, with small effects on the low-band operation. Two wide operating bands are hence easily obtained and adjusted. The antenna can also be recessed in a small ground clearance of 10 × 35 mm
²
inside the tablet device such as a tablet computer in this study. Details of the proposed antenna are presented.