Printed multi-resonant antenna embedding two inductors in radiating strips for internal mobile phone LTE/WWAN operation

Abstract

In this article, a planar printed antenna for eight-band LTE/WWAN operation applied in the internal mobile phone has been proposed and studied. The presented antenna consists of a feeding strip and a coupling strip, where two chip inductors with different inductances are loaded in place. The desired lower bands of LTE700/GSM850/900 operation can be achieved by the coupling strip loading an inductor of 12 nH and a longer branch loading another inductor of 24 nH in the feeding strip, which provide a quarter-wavelength dual-resonance mode at 720 and 900 MHz. While a quarter-wavelength resonant mode at around 2.95 GHz can be generated by the shorter branch of the feeding strip, and other resonant modes at 1.92 and 2.23 GHz are contributed by the higher-order resonant modes of the long feeding strip and coupling strip, covering the desired upper bands of DCS1800/PCS1900/UMTS2100/LTE2300/2500 operation. In fact, the desired resonant lengths in the lower frequencies can be decreased, and impedance matching can be properly adjusted with the help of the two embedded inductors. Besides, a chip inductor of 2.2 nH is helpful for improving all the bands’ impedance matching. Detailed considerations of the antenna design and main parameters are studied and measured.