Plane-wave Shielding Effectiveness Research Articles

Accurate Measurement of the True Plane-Wave Shielding Effectiveness of Thick Polymer Composite Materials via Rectangular Waveguides.

This paper presents a methodology for accurately gauging the true plane wave shielding effectiveness of composite polymer materials via rectangular waveguides. Since the wave propagation of the waveguides is not in the form of plane wave patterns, it is necessary to post-process the S-parameters for the measured data of the waveguide lines to obtain such patterns and ascertain the effectiveness of true plane wave shielding. The authors propose two different methods to achieve this. The first applies simple renormalization of S-parameters, where reference impedance is changed from the value for the waveguide to that for free space, which ensures good accuracy of shielding effectiveness with a small degree of discontinuity across the range of frequencies. The other relies on rigorous extraction of the composite materials’ effective permittivity and permeability ascertained from rectangular waveguides; afterward, plane wave shielding effectiveness is calculated analytically and gives very high accuracy. Both procedures assume the given samples are isotropic in character. We validated the accuracy of the methodologies by conducting tests on a set of synthetic samples of 2 mm thickness with unit permittivity and variable conductivity and on a dielectric material of known permittivity (FR4 laminate). The applicability of both methods was further proven by analyzing the isotropic composite materials, a process involving the use of iron particles embedded in a dielectric matrix. The synthetic samples and an FR4 material were tested to check the accuracy of the methods. Based on numerical studies and measurements, we concluded that materials with a shielding effectiveness of up to 25 dB could be measured at a maximum amplitude error of 1 dB to 3dB to a frequency of 18 GHz, depending on the relative permittivity of the material; hence, the first method was suitable for approximation purposes. For maximal accuracy, the second method typically demonstrated an amplitude error of below 0.5 dB to the same frequency across the entire range.

The Shielding Effectiveness of a Narrow Slot Exposed to a Nearby Dipole Source and a Plane Wave

This paper presents the shielding effectiveness (SE) characteristics of a metallic wall with a narrow slot when exposed to a nearby dipole source or a plane wave. In order to characterize the dipole source SE, a radiation field, including the near field from the dipole source, is calculated. The results show that the dipole source SE depends on the source and field points. This SE is different from the plane wave SE in that it fluctuates with the position of the dipole source; the fluctuation period is about 0.5λ.

Comments on "Shielding effectiveness of conductive polymers

The authors comment that K. Naishadham (see ibid., vol.34, no.1, p.47-50, 1992) calculated the plane-wave shielding effectiveness of conductive polymers as a function of frequency. As indicated, a comparison to the measured result of the DC conductivity indicates that the microwave conductivity at room temperature is within a small percentage of the DC result, and therefore can be used for a wide frequency range. The conductivity of the polymers is given by /spl sigma/=2/spl pi/f/sub 0//spl epsiv//sub 0//spl epsiv/ and is assumed invariant for all frequencies. Based on the invariability of polymers' conductivity for all frequencies, they calculated the shielding effectiveness of the polymers. Discrepancies are found by comparing these figures to those of Naishadham. It is concluded that shielding effectiveness calculated by Naishadham was done under the assumption of frequency-invariant /spl epsiv/ instead of /spl sigma/.

Electromagnetic shielding behavior of wire-mesh screens

The electromagnetic shielding behavior of bounded-junction wire-mesh screens is discussed in the frequency range where the individual meshes are electrically small. The screen, whose meshes are assumed to be square, is described by a equivalent sheet impedance operator. The plane-wave shielding effectiveness of a planar-mesh screen is derived. The problem of coupling between antennas on either side of the planar mesh is addressed, and its applicability to the measurement of mesh properties is described. The low-frequency electric and magnetic shielding afforded by mesh enclosures is considered. Because of the reactive character of the mesh surface, the plane-wave shielding effectiveness decreases with increasing frequency. The enclosure's magnetic-field shielding effectiveness increases with increasing frequency, but saturates at a maximum value that depends on the geometry of the enclosure, the mesh size, and the mesh wire radius. The enclosure electrostatic-field shielding effectiveness depends only on the enclosure and mesh geometries.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Thin-Film Shielding for Microcircuit Applications and a Useful Laboratory Tool for Plane-Wave Shielding Evaluations

The results of plane-wave shielding effectiveness tests on vacuum deposited metallic thin films are discussed. The test data are presented in graphical form for thin films of copper, aluminum, silver, gold, and nickel. Shielding effectiveness as high as 90 dB was obtained. In addition, a novel test instrument and measurement technique were devised for this study. The test procedure is described, design information for the construction of the test device is given, and a theoretical basis for its use is presented.

Plane-wave shielding effectiveness studies of thin films

A novel technique for determining the plane-wave shielding effectiveness of thin films utilizing a TEM mode structure has been previously described. This letter presents some of the results obtained. In addition, note is made of an error which existed in the original measurement setup and its effect on the results is discussed.

A useful technique for evaluating the plane-wave shielding effectiveness of thin films

A useful technique for evaluating the plane-wave shielding effectiveness of thin films