Internal compact printed loop antenna for WWAN/WLAN/ISM/LTE smartphone applications

In this paper, we designed and developed a novel internal compact printed loop antenna for WWAN/WLAN/ISM/LTE smartphone applications. The proposed antenna is composed of a meander loop antenna and a capacitively coupled feeding line. It has a planar structure, with an overall dimension of 120 × 60 mm2, the antenna portion occupying a size of 20 × 60 mm2, which makes it suitable for practical smartphone applications. The results of our measurement reveal that the prototype antenna can provide two wide frequency bands of 712–1078 and 1757–2930 MHz, which cover multi-band for GSM850/GSM900/DCS1800/PCS1900/UMTS2100/IMT2000/WLAN2400/ISM2450/LTE700/LTE2300/ LTE2500. The antenna also shows good radiation characteristics and gain peaks for frequencies over the desired operating bands. We also studied the specific absorption rate (SAR) of the proposed antenna placed at the bottom of a mobile phone. The obtained SAR values are all below the SAR limit of 1.6 W/kg for the 1 g head tissue and 2.0 W/kg for the 10 g head tissue. We used CST Microwave Studio and Ansoft HFSS for the simulation and the design of the antenna and present in this paper the details of the design considerations, as well as the results on the reflection coefficient, the surface current distributions, the radiation characteristics, and the gain of the proposed antenna.