Design, Construction and Validation of a High-Performance OATS

The state of the art on the open-area test site (OATS) has been introduced. Key technologies on the design and validation of a high-performance OATS have been provided. Some famous OATS in the world regarding their structure, the dimensions of the ground plane (GP), the location of the control room, and performance are listed in a table. A case study is provided on NIM’s high-performance OATS. Many details are open for the first time, which show the fine design. A measurement uncertainty example has been provided in measuring the free-space antenna factor of biconical antennas. These results are based on the author’s many years of experience, with lots of valuable data and photos. It is intended for calibration laboratories, for EMC antenna users, for writing EMC standards, as well as for the assessors in EMC.

Investigation of Broadband Printed Biconical Antenna with Tapered Balun for EMC Measurements

This article investigates the design, modeling, and fabrication of small-size (150 × 90 × 1.6 mm) broadband printed biconical antenna. The proposed antenna is intended for use a reference antenna for electromagnetic interference measurement inside the EMC chamber. The reflection coefficient (S11-parameter) is verified by modeling the equivalent circuit of the structure in terms of lumped elements. This structure offers a −10 dB impedance bandwidth (from 0.65 GHz to 2.3 GHz) with the tapered balun feeding method. Therefore, it has a high probability of estimating the electromagnetic waves emitted from several applications such as GSM, LTE, UMTS, 3G, Wi-fi, Bluetooth, ZigBee and more. The simulated standard antenna parameters are compatible with the measured parameters results. Furthermore, azimuth omnidirectional radiation pattern and well-realized gain (3.8 dBi) are achieved, reflecting good values of antenna factor compared to the commercial design.

Design of a Miniaturized Rectangular Multiturn Loop Antenna for Shielding Effectiveness Measurement

This paper proposes a novel miniaturized rectangular loop antenna sensor consisting of a multiturn wire and a cuboid ferrite core. The lateral surface of the ferrite core is tightly wound by the multiturn wire. To verify its feasibility, the antenna sensor is fabricated, and the antenna factor (AF) levels are measured using the three-antenna method from the very low frequency (VLF) to the high-frequency (HF) bands. The measured AF levels are 31.8 dB (with a covering plastic case) and 33.1 dB (without a covering plastic case) at 30 kHz. In addition, the proposed antenna is employed in the shielding effectiveness measurement of a small commercial cabinet to observe its suitability for shielding effectiveness (SE) measurement of small shielding enclosures. The SE values averaged over the frequency range from 10 kHz to 3 MHz are 4.1 dB and 12 dB in the horizontal and vertical polarizations, respectively.

Results of the national antenna intercomparison 2017/2018 within the German Calibration Service (Deutscher Kalibrierdienst – DKD)

In an intercomparison organized within the framework of the German Calibration Service (Deutscher Kalibrierdienst – DKD), seven different calibration laboratories participated in the measurement of the antenna factor for three different antennas according to different standards. Between August 2017 and April 2018, measurements have been performed on a hybrid antenna, a logarithmic-periodic antenna and on an Open Ended Waveguide.

Calibration Proposal for UHF Partial Discharge Measurements at Power Transformers

The continuous, non-intermitted service of electrical grids relies on the reliability of their assets, e.g., power transformers. Local insulation defects can result in serve failures such as breakdowns with severe subsequent costs. The prevention of such events is crucial. Hence, partial discharge (PD) activity at power transformers is evaluated directly in the factory before shipment. Additionally, PD activity can be monitored during service using the ultra-high frequency (UHF) method. In this contribution, a calibration procedure is proposed for the UHF method. The calibration process is required to ensure both, reproducibility and comparability of UHF measurements: Only a calibrated UHF measurement procedure can be introduced supplementary to IEC 60270 in acceptance tests of power transformers. The proposed calibration method considers two factors: The influence of the UHF-antenna’s sensitivity and the PD recorder characteristics including accessories such as cable damping, pre-amplifier, etc. The former is addressed by a characterization of UHF sensors using the standard antenna factor (AF) in a gigahertz transverse electromagnetic (GTEM) cell. The PD recorder’s influence is corrected by using a defined, invariable test signal as reference for all recording devices. A practical evaluation of the proposed calibration procedure is performed in a laboratory setup using different UHF recording devices and UHF sensors using artificial PD signals and real voltage-driven PD sources.

PERFORMANCE ANALYSIS FOR DIRECTION-FINDING CIRCULAR ANTENNA ARRAY

This paper considers circular antenna arrays comprised of symmetrical dipole radiators applied in communication, navigation and monitoring systems. Despite their widespread use, a number of significant issues is underinvestigated. Among them are frequency dependence of the antenna factor (the ratio of the electric field intensity module to the voltage amplitude at the load connected to the output terminals) of the circular antenna array elements in the correct electrodynamic setting. The purpose of this paper is to analyse the antenna factor frequency dependence of a single dipole antenna with different geometry and load both in free space and as circular antenna element. The estimation of phase difference error between the circular antenna array elements caused by their cross coupling is also of interest.Specific expressions are obtained for the antenna factor of the dipole antenna for single-mode and three-mode approximations. The limits of their applicability in frequency band are considered. The solution to the coupled integral equations is obtained using the Galerkin method with piecewise sinusoidal current distribution and with an arbitrary number of basis functions for eight- and four-element circular antenna array. This solution may be generalized to an arbitrary number of circular antenna array elements. It is demonstrated that to improve the antenna factor frequency dependence it is advisable to use dipole antennas with high-resistance load, as well as with large diameter. Phase errors for different circular antenna array element signals are considered with respect to the reference element. The dependence of these phase errors on the circular antenna array geometry is presented. It is concluded that there are significant oscillations of the antenna factor when the dipole is the part of the circular antenna array. They are caused by cross coupling between the circular antenna array elements, which significantly depend on the element spacing. The results presented may be of interest to phase direction finder development engineers.