Field analysis of penetrable conductive shields by the finite-difference time-domain method with impedance network boundary conditions (INBCs)

Impedance network boundary conditions (INBCs) are implemented in the finite-difference time-domain (FDTD) method to analyze the electromagnetic field around penetrable shield structures. The shield region is eliminated from the computational domain and the INBCs are applied on the new boundary surfaces, i.e., shield surfaces, to take into account the field discontinuity produced by the shield. The INBCs represent an important extension of the well-known surface impedance boundary conditions (SIBCs) since the INBCs model accurately the coupling of the electromagnetic fields through penetrable shields and lead to a significant reduction of the number of the FDTD unknowns. The INBC expressions are given analytically in both frequency and time domains, and the INBC implementation in a FDTD code is discussed. The proposed INBC-FDTD method is numerically efficient because the resulting convolution integrals are recursively solved. Furthermore, approximate time-constant INBCs are proposed which are valid for many practical applications. The analysis of transient electromagnetic fields around penetrable conductive shields in simple test configurations are presented and compared with the analytical solution

A Microstrip Array of Aperture-Coupled Patches for UMTS Base Stations

The rising popularity of wireless communication systems has induced a demand for more and more efficient systems, able to serve larger numbers of users, to provide higher transmission speeds and to operate in more complex environments. The present limited available bandwidth and the growing request for capacity require new channels to be multiplexed. This objective can be accomplished by employing smart antenna systems at the base station. A smart antenna can be used to direct the main beam toward the desired user and to set pattern s in the direction of interferers. Such a system can be seen as channel multiplexing in the spatial domain, which increases both carrier-to-interference ratio (C/I) and system capacity. Moreover, it is important to note that dual-polarization sensors provide a diversity scheme. In this framework, plusmn;45 deg; slanted polarizations are preferred to vertical/horizontal (V/H) polarizations because they form identical azimuthal patterns and are equally sensible to horizontally and vertically polarized signals. A dual-polarized microstrip array panel is proposed, which can be used as a smart antenna in the framework of Universal Mobile Telecommunication Systems (UMTS)

A new hybrid technique for field evaluation inside a biological medium

The accurate evaluation of the electromagnetic field inside a human head due to the radiation of a cellular telephone is a challenge that is involving many research group all over the world. Some numerical methods are used to cope with this problem, but each of them has some limitation. The method proposed is a combination of the Method of Moment (MoM) in time domain and the FDTD, for the combination of the two permits to overcome the intrinsic limitation of each of them. In particular it permits a better description of the source (by MoM) and the human head (by FDTD)

A wideband dual-polarized stacked patch antenna for base stations

This paper proposes a wideband dual-polarized slot-coupled stacked patch antenna operating at UMTS, WLAN (2.4 GHz) and UMTS II frequency bands. The antenna has been designed and optimized by using Ansoft Designertrade. A prototype has been realized and measurements were carried out showing good performance in the whole required bandwidth (33.4% bandwidth

Measurement system for thin shield effectiveness

In this paper an optimization of the set-up for the shielding effectiveness measurement of a closed thin enclosure is shown. Various sort of noise, due to the measuring set-up, can superimpose to the signal of interest, making difficult to recover it from what is received by the instruments. A complete analysis of the problems that arise in the case of ESD, CW conducted and CW radiated excitations is presented, together with their solutions

MoM-FDTD hybrid technique for analysing scattering problems

The authors present a new hybrid technique for analysing complex electromagnetic problems, combining a marching on in time version of the MoM and the FDTD. The use of the equivalence principle allows the problem to be separated into two simpler problems, and a proper set of equivalent sources is defined to account for the coupling between actual sources and scatterers

A wideband dual-polarized stacked patch antenna

A wideband dual-polarized slot-coupled stacked patch antenna operating in the UMTS (1920–2170 MHz), WLAN (2.4–2.484 GHz), and UMTS II (2500–2690 MHz) frequency bands is described. Measurements on a prototype of the proposed patch antenna confirm good performance in terms of both impedance matching and isolation

Development of a hybrid MOMTD/FDTD technique for EMC problems: Analysis of the coupling between ESD transient fields and slotted enclosures

The penetration of the field radiated by an indirect ESD into a shielded enclosure through an aperture has been analysed by a new hybrid numerical technique. In fact, the combination of the marching on in time version of the Method of Moment (MoMTD) and the Finite-Difference Time-Domain (FDTD) method allows to study more efficiently and accurately typical EMC problems. In particular, the use of the equivalence principle with a proper set of fictitious currents (accounting for the coupling) permits to divide the complex original problem into two simpler problems: the radiation of the source, analysed by MoMTD, and the field scattering outside and inside the slotted shield, studied by FDTD method. The validation of the model is assessed by setting up an accurate measurement in a well controlled environment using a network analyser. It consists of a monopole on a ground plane, fed by a voltage pulse that radiates a perfectly conducting box with a small horizontal aperture, facing the antenna in its near field region. The numerical results are compared with those from experiment and show a good agreemen

Differential planar antennas for 2.4/5.2 GHz WLAN applications

In this paper, three different configurations of planar antennas with a 100 Omega differential input impedance for dual-band WLAN applications, have been designed and compared. The proposed antennas provide dual-band operation in the 802.11a/b/g frequency bands without using a balun (balanced feeding). The best return loss performance has been obtained with the dual-band printed dipoles which are also characterized by a relatively straightforward design and tuning procedure. Measurements on constructed prototypes are shown at the conferenc