A coupled-fed loop antenna with Octa-bands operation for long-term evolution (LTE) smartphones is proposed in this paper. The antenna occupies a nonground space of only 6.5 mm × 72 mm, and two wide-band operations can be achieved by exploiting the multimode characteristics of loop antenna and using high-pass matching circuits. In low band, the LTE700/GSM850/900 operation is achieved by the loop mode of 0.5
Mobile long-term evolution (LTE) smartphone has become an essential equipment for daily life bringing a lot of convenience due to its integrated multifunction services, for example, mobile communications, surfing the Internet, GPS location, and e-payment. The increasing application area will become more and more obvious in the future. As a critical component of mobile smartphones, the antennas with various configurations have been investigated widely to cover multiple frequency bands maturing 2G/3G/4G wireless communication services [
The design configuration of handset antennas can be basically categorized into four distinct types: The first type uses coupled-fed monopole antenna configuration for wideband or multiband applications [
In this paper, an Octa-band loop antenna with two wide operating bands and a very small nonground height of only 6.5 mm is presented. The lower band has a bandwidth of 0.7 GHz to 1.03 GHz (0.33 GHz or 38.2% bandwidth) to cover the LTE700/GSM850/GSM900 systems, whereas the upper band from 1.7 GHz to 2.69 GHz (0.99 GHz or 45.1% bandwidth) covers the DCS1800/PCS1900/UMTS/TD-SCDMA/LTE2300/2500 systems. The performance of the antenna is studied using the ANSYS high-frequency structure simulator (HFSS). A prototype of the antenna is fabricated and measured to verify the design.
Figure
Geometry and dimensions of the proposed antenna. (a) Top view of the wideband antenna for Octa-band LTE/WWAN operation. (b) Enlargement dimensions of the metal pattern in the antenna area.
The loop antenna is composed of an unequal-arm T-shaped driven strip and a single-folded loop structure. It should be mentioned that the loop configuration differs from the reported loop antenna in the open literatures [
Vector current distribution of the proposed antenna at frequencies of 0.9 GHz, 1.8 GHz, 2.1 GHz, 2.3 GHz, and 2.64 GHz.
To better understand the influence of the design parameters on the performance of the antenna, a parametric study was carried out.
Figure
Simulated reflection coefficient for the proposed antenna as a function of the ratio between
Figure
Effect of the ration
The effect of varying the parameter
Simulated reflection coefficient for the proposed antenna as a function of
Figure
Simulated reflection coefficient for the proposed antenna as a function of (a)
Figure
Effect of the ground plane on the reflection coefficient. (a) Width of the ground plane. (b) Length of the ground plane.
The simulation results were verified by fabricating and testing a prototype of the proposed design with the dimensions provided in Figure
(a) Fabricated antenna and (b) comparison of simulated and measured reflection coefficient of the proposed antenna.
Measured and simulated reflection coefficients for the proposed antenna are compared in Figure
Figure
Normalized radiation patterns at two resonant frequencies: (a) 0.9 GHz and (b) 1.8 GHz.
The simulated and measured gain and efficiency in the lower and upper bands are presented in Figure
Simulated and measured peak realized gain and efficiency.
In this paper, a compact coupled-fed loop antenna with six resonant modes for mobile smartphones was proposed. The distinguishing attribute of the proposed antenna is that both front ends of the folded loop line are connected to system ground plane and the loop is fed capacitively by an unequal T-shaped strip to produce two wide operating bands. The dual resonance in the lower band, covering GSM850 and GSM900 bands, is provided by the half-wavelength loop mode in combination with a high-pass circuit. Other high-order modes of the entire loop line and the 0.5
The authors declare that they have no conflicts of interest.
This work was supported by the Mainland Hong Kong, Macau, and Taiwan Science and Technology Cooperation Projects (2015DFT10170), the Science and Technology Research Project of Chongqing Municipal Education Committee under Grant no. KJ1600409, and the Doctoral Fund of Chongqing University of Posts and Telecommunications (A2015-08).