Antenna Systems & Technology - Fall 2012 - (Page 6)

FEATURE ARTICLE Performance Evaluation of Antenna Integration on Mobile Devices Through Full-Wave Analysis By Rensheng Sun, Ph.D, Senior Application Engineer • EM Software & Systems (USA), Inc. The increasing prevalence of handheld mobile devices such as smartphones and tablet computers provides both opportunities and challenges to antenna design engineers nowadays, because the designers not only need to have antennas cover multi-band and/or multi-purpose communications as standalone elements, they are also required to make sure the antennas perform well after the integration into the devices. Very often, full wave analysis needs to be carried out to study the mutual couplings between multiple antennas in addition to their radiation characteristics, considering the effects not only from handset case and LCD, but also from many other components, such as battery, speaker, PCB, etc. space is required, and the efficiency of the FEM for the treatment of inhomogeneous dielectric bodies. The approach proves to be especially efficient when both transmitter and receiver need to be included in the same modeling session. It is also a preferred method for bioelectromagnetic problems such as radiation hazard with specific absorption rate (SAR) calculations. Dual-Band WLAN Antenna Hybrid FEM/MoM As one of the most popular full-wave analysis approaches that solve Maxwell’s Equations for high frequency electromagnetic problems, the finite element method (FEM) is intrinsically suitable for such problems since it is very efficient on modeling 3D volumes that have complex geometrical details and material inhomogeneities. However, as FEM formulation doesn’t incorporate the Sommerfeld radiation condition, usually the radiation condition in FEM implementations is applied using appropriate absorbing boundary condition (ABC), or perfectly matched layer (PML) technique. This requires the domain of discretization be extended far from the source region. The integral equation method such as Method of Moments (MoM) is an ideal formulation for open boundary radiating/scattering structures. As a result, the domain of discretization can be kept to a minimum. The hybrid FEM/MoM exploits the benefits from both techniques: the efficiency of the MoM for the treatment of open boundary radiating structures because no discretization of three-dimensional (3-D) In this study, a dual-band flat-plate antenna was extracted from the commercial software Antenna Magus for the quick creation of the antenna model. The antenna design was originally proposed [1] with a shorted parasitic strip element to widen the upper band such that the antenna covers both 2.4 GHz and 5.2/5.8 GHz bands. The model was then loaded into the software FEKO for full-wave analysis. Figure 1 shows the triangular mesh generated for MoM solver in FEKO, with enlarged view on the radiating strips where finer mesh was created to better capture the surface current distribution. After running the MoM solver in FEKO, the reflection coefficient as a function of frequency was plotted and shown in Figure 2. Figure 3 and Figure 4 illustrate the computed surface currents and radiation patterns for the antenna at 2.4 GHz and 5.5 GHz respectively, before it’s integrated into the mobile device. Performance Evaluation of the Antenna at Device Level Once the antenna is integrated into the mobile devices such as smartphones or tablets, the effect of surrounding components from near-field environment has to be considered, as the overall performance of the antenna will get degraded if no adjustment is made. More efforts are typically needed for 4G LTE and 802.11n applications as MIMO is required and the coupling/isolation Figure 1. Meshed antenna with enlarged view on radiating strips. Figure 2. Computed S11 for the WLAN antenna. 6 ANTENNA SYSTEMS & TECHNOLOGY FALL 2012 WWW.ANTENNASONLINE.COM http://WWW.ANTENNASONLINE.COM

Table of Contents for the Digital Edition of Antenna Systems & Technology - Fall 2012

Antenna Systems & Technology - Fall 2012
Table of Contents
Editor’s Choice
Performance Evalutaion of Antenna Integration of Mobile Devices Through Full-Wave Analysis
Base Station Antenna Evolution and Revolution
Antennas
Mobile Antenna Systems 2012 - Conference Preview
Manufacturing/Design
Components
Test & Measurement
Wireless Communication
Industry News
Marketplace

Antenna Systems & Technology - Fall 2012