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In this paper, a reexamined estimate of the test fixture validation factor (TFVF) of fixtures for shielding effectiveness (SE) measurements in a reverberation chamber is shown. The fundamental conditions for the applicability of the model shown here are a large aperture between the chambers, whose transmission cross section is well approximated by the geometrical optics, and an isolation between the chambers greater than or equal to 10 dB, as specified in this paper. The model is applicable for both nonmarginal and marginal SE values; but, in the latter case, the requested isolation between the two chambers has to be met with no sample in the aperture. For nonmarginal SE values, the conditions requested for the applicability of the model are practically the same as those requested in the standard IEC 61000-4-21. The model is applicable to SE measurements of gaskets as well. The results show that the TFVF used in the standard procedure IEC 61000-4-21 has to be updated to achieve more accurate measurements of SE in light of the studies conducted on this topic. We give such an update in this study. [ABSTRACT FROM AUTHOR]

As we know, air breakdown would occur if the power of a microwave pulse, which radiates from an aperture antenna, was high enough, the transmission of microwave could be hindered. Based upon this assumption, this paper intends to report on the mathematical deduction of the maximum power radiated from an aperture antenna before air breakdown in the near-field region. It also presents the calculations in the power density enhancement factors corresponding to different kinds of aperture field distributions in the near-field region of a circular cophasal aperture. In addition, this paper also proposes a formula by the field equivalence principle for calculating the normalized power density on axis. The results showed that the air breakdown in the near-field region could be a limiting factor for the maximum power, depending on aperture radius, the field distribution in the aperture plane, the frequency, and the pulse width of a microwave pulse. [ABSTRACT FROM PUBLISHER]

We discuss a fundamentally new method for electric (E) field strength (V/m) metrology applicable to the near-field. This new approach is significantly different from currently used field measurement techniques in that it is based on the interaction of radio-frequency (RF) E-fields with Rydberg atoms (alkali atoms placed in a glass vapor cell that are excited optically to Rydberg states). The applied RF E-field alters the state of the atoms. The Rydberg atoms act like an RF-to-optical transducer, converting an RF E-field strength to an optical-frequency response. In this new approach, we employ the phenomena of electromagnetically induced transparency (EIT) and Autler-Townes splitting. The RF transition in the four-level atomic system causes a split of the EIT transmission spectrum of a probe laser into two peaks. This splitting is easily measured and is directly proportional to the applied RF E-field amplitude. The significant dipole response of Rydberg atoms enables this technique to make self-calibrating measurements over a large frequency band including 500 MHz to 500 GHz (and possibly up to 1 THz and down to 10s of megahertz). In this paper, we report on our results in the development of this metrology approach, including the first fiber-coupled vapor-cell for E-field measurements. We also discuss key applications, including self-calibrated measurements, millimeter-wave and sub-THz measurements, field mapping, and sub-wavelength and near-field imaging. We show results for mapping the fields inside vapor cells, for measuring the E-field distribution along the surface of a circuit board, and for measuring the near-field at the aperture in a cavity. We also discuss the uncertainties of this measurement technique. [ABSTRACT FROM PUBLISHER]

This paper presents an accurate model of a circular aperture with full parabolic-in-square aperture distribution that can be applied to reflectors, antenna arrays, microwave lenses, or other aperture antennas. The proposed aperture distribution is a weighted sum of the parabolic in square on a pedestal and parabolic tapered distributions. It permits the analysis and design of efficient aperture antennas with a low sidelobe level. The main far-field parameters of antenna radiation, aperture taper efficiency, directivity, radiated power, half-power beamwidth, and sidelobe level can be determined with simple formulas. Additionally, the applied aperture distribution permits accurate near-field estimation. A new analytical solution of the Helmholtz equations for an on-axis near field is derived. A comparison of the obtained solution with known analytical results based on the Fresnel approximation is presented. Verification of the new near-field formula favorably coincides with near-field numerical simulations using electromagnetic software FEKO. [ABSTRACT FROM PUBLISHER]

In this paper, Robinson's analytical formulation is extended to calculate the shielding effectiveness of an shielding enclosure at off-axis observation points with an off-axis aperture. First, we give the procedure of extending the original analytical formulation. Then, the transmission-line matrix method (TLM) is utilized to validate the extended analytical formulation. The application range of the extended method is decided by comparing to TLM, and the good agreement between the results calculated by two methods indicates that the extended analytical formulation is efficient in predicting the shielding effectiveness of an enclosure at different observation points with an off-axis aperture. Through the intensive calculation and analysis, the distribution of SE inside the enclosure and the variation of SE with aperture position can be obtained, which may be used as a guideline for designing shielding enclosures. [ABSTRACT FROM AUTHOR]

A statistical modeling technique known as the random coupling model (RCM) is an effective method for estimating the probabilistic magnitudes of induced voltages on objects within a closed, complex, three-dimensional (3-D) enclosure. The limitations of the RCM to predict electromagnetic wave coupling into an enclosure with apertures are examined. We experimentally demonstrate the applicability of the RCM to estimate the probabilistic magnitudes of voltages induced on ports in a complex 3-D enclosure with an electrically large aperture. This study is a first step toward being able to predict effects on sensitive electronic targets in large, real-world, lossy enclosures such as office buildings, ship compartments, and aircraft compartments. [ABSTRACT FROM PUBLISHER]

An asymmetric wideband dual-polarized bilateral tapered slot antenna (DBTSA) is proposed in this letter for wireless EMC measurements. The DBTSA is formed by two bilateral tapered slot antennas designed with low cross polarization. With careful design, the achieved DBTSA not only has a wide operating frequency band, but also maintains a single main-beam from 700 MHz to 20 GHz. This is a significant improvement compared to the conventional dual-polarized tapered slot antennas, which suffer from main-beam split in the high-frequency band. The innovative asymmetric configuration of the proposed DBTSA significantly reduces the field coupling between the two antenna elements, so that low cross polarization and high port isolation are obtained across the entire frequency range. All these intriguing characteristics make the proposed DBTSA a good candidate for a dual-polarized sensor antenna for wireless EMC measurements. [ABSTRACT FROM AUTHOR]

A formula is derived for the field excited in a perfectly conducting rectangular cavity by an external field incident on a small aperture or localized group of apertures in a cavity wall. It is assumed that the cavity is part of a larger system and that a separate estimate has been made of the external field near the aperture. The formula is shown to produce results in good agreement with results derived using specialized codes. [ABSTRACT FROM AUTHOR]

A simple circuital approach to evaluate the shielding effectiveness (SE) of rectangular enclosures with apertures is proposed, considering oblique incidence and polarization. The scope of the proposed model is extended beyond 1 GHz, including higher order modes of the cavity. Furthermore, apertures are not required to be on the front face of the enclosure. In the proposed model, the SE of the enclosure with apertures on multiple sides can be simply calculated by vector decomposition. The proposed model has been successfully verified by using a conventional full-wave simulation tool. We also measured the SE of a manufactured aluminum enclosure with apertures on multiple sides. [ABSTRACT FROM AUTHOR]

In this work, an assessment of the influence of the field probes on the uncertainty in the measurements of the electric and magnetic field in the vicinity of aperture antennas is presented. A uniform aperture distribution is considered because the field of a tapered distribution aperture can be reduced to that of a uniform one. Moreover, the effect of probe size and configuration is presented through a comparison between the theoretically calculated and the expected values. Field probes of a single or more perpendicular dipoles are investigated. The maximum permissible length of the dipoles for an accurate field assessment depends on the field's gradient. In the regions where the relative amplitude and phase of the electric field along the measuring device does not exhibit considerable variation, even half-wavelength dipoles can be used. It is also found that probes with sizes less than 0.1λ ensure measurement uncertainty less than 0.5 dB for field variation up to 7 dB/λ. [ABSTRACT FROM AUTHOR]