In this article, a coupled-fed planar printed antenna mounted on the compact no-ground portion of the system circuit board of a mobile phone with a low profile of 10\,mm is proposed and studied. The presented antenna is formed by a double-branch feeding strip, a shorted coupling strip with two open-ended loops of different lengths, and a slotted ground structure consisting of two monopole slots, yet it has a size only 15×50 mm2. Two wide operating bandwidths of 698--960\,MHz and 1710-2690 MHz can be achieved by these radiating strips, which provide multiple resonant modes at about 750, 1000, 1750, 2300 and 2900 MHz. In addition, with the presence of the two narrow slots and a chip inductor (L = 1.5 nH), in this study, the printed antenna can lead to much widened bandwidths in both the antenna's lower and upper bands to cover LTE700/GSM850/900 and DCS1800/PCS1900/UMTS2100/LTE2300/2500, respectively. Good radiation efficiency and antenna gain for frequencies over the desired operating bands are obtained. Detailed design considerations of the proposed antenna are described, and both experimental and simulated results are also presented and discussed.
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