Folded, Low Profile Multiband Loop Antenna for 4G Smartphone Applications

A folded, low profile and compact multiband loop antenna suitable for 4G smartphone applications (LTE700, LTE2500 and LTE3400) is proposed. The antenna is simply fed by direct parallel feed for better matching. The greatest highlights of the proposed antenna are: 1) it provides multiband antenna solution with a broadband solution below 1 GHz; 2) it is compact and has a small footprint size 65 (L) x 7.5 (W) x 4.5 (H) mm^3. The compactness is achieved using two techniques: a capacitive loading due to the added strips inside the loop, and the bending or the folding of the loop by a right angle. Detailed design considerations are described; and both simulated and measured results are also presented and discussed.