Victor Khilkevich

An Effective Method of Probe Calibration in Phase-Resolved Near-Field Scanning for EMI Application

Near-field scanning can be used to determine the far-field emissions of electronic devices. In general, this requires phase-resolved electric and magnetic near-field data. To capture a broad frequency range relatively quickly, a multichannel oscilloscope can be used for data capture. The phase relationship of the fields between different space points and between the electric and the magnetic field needs to be known. Consequently, it is required to determine the complex-valued probe factor (PF) of the probe, cable, and amplifier chain. This paper presents a fast and efficient calibration method which uses the same setup and instruments during calibration and measurement, and it allows for easy and economical integration of the calibration hardware and software into the scanning system. Known fields are created by a microstrip trace driven with a comb generator. By referencing measured data to this known field, the PF is obtained over a broad frequency range by capturing one time-domain waveform.

Estimating Radio-Frequency Interference to an Antenna Due to Near-Field Coupling Using Decomposition Method Based on Reciprocity

In mixed radio-frequency (RF) and digital designs, noise from high-speed digital circuits can interfere with RF receivers, resulting in RF interference issues such as receiver desensitization. In this paper, an effective methodology is proposed to estimate the RF interference received by an antenna due to near-field coupling, which is one of the common noise-coupling mechanisms, using decomposition method based on reciprocity. In other words, the noise-coupling problem is divided into two steps. In the first step, the coupling from the noise source to a Huygens surface that encloses the antenna is studied, with the actual antenna structure removed, and the induced tangential electromagnetic fields due to the noise source on this surface are obtained. In the second step, the antenna itself with the same Huygens surface is studied. The antenna is treated as a transmitting one and the induced tangential electromagnetic fields on the surface are obtained. Then, the reciprocity theory is used and the noise power coupled to the antenna port in the original problem is estimated based on the results obtained in the two steps. The proposed methodology is validated through comparisons with full-wave simulations. It fits well with engineering practice, and is particularly suitable for prelayout wireless system design and planning.

Attenuation in Extended Structures Coated with Thin Magneto-Dielectric Absorber Layer

Thin absorbing layers containing magnetic alloy or ferrite inclusions can be efiectively used for attenuating common-mode currents on extended structures, such as power cords, cables, or edge- coupled microstrip lines. An analytical model to evaluate attenuation on the coaxial line with the central conductor coated with a magneto- dielectric layer is proposed and validated by the experiments and numerical modeling. The analytical model is validated using available magneto-dielectric samples of difierent thicknesses. This model can serve for comparing and predicting the absorptive properties of difierent samples of magneto-dielectric materials, whose compositions may be unknown, but dielectric and magnetic properties can be determined by independent measurements over the specifled frequency ranges. From modeling the absorption in a coaxial line with a wrapped central conductor, it could be concluded whether it is reasonable to use this particular material in such applications as a shield on an Ethernet or other cable, for reducing potential common-mode currents and unwanted radiation in the frequency range of interest.

Modeling absorbing materials for EMI mitigation

In this study, the parameters of magnetic absorbing materials were measured and used to predict their effectiveness at reducing total radiation power from a heat sink. The parameters of absorbing materials were measured using a transmission line method and fitted using the Debye model. By comparing S-parameters and power loss between a simulated and measured microstrip line, the fitted material parameters were validated. The heat sink model has also been investigated to determine the radiation mitigation with lossy materials.

Measurement-Based Modeling and Worst-Case Estimation of Crosstalk Inside an Aircraft Cable Connector

Crosstalk within cable bundles can degrade system performance. In aircraft systems that use shielded twisted pairs, the crosstalk occurs primarily in the connector where individual signal wires are not shielded or twisted. In many cases, the parameters which determine crosstalk within the connector are unknown because the connector is closed and wires cannot be easily accessed. Expanding on prior research [14], a methodology for measuring coupling parameters and modeling crosstalk within aircraft cable connectors at low frequencies (<;400 MHz) was developed. The values of mutual inductance and capacitance were extracted from measurements made with a vector network analyzer (VNA). The characteristics of the individual wires were extracted from VNA-measured TDR response. The accuracy of the model was evaluated through comparison of simulated and measured results. Additionally, a closed-form solution was developed to estimate the worst-case envelope of the differential crosstalk. The calculated results match the measured peak values well. This worst-case crosstalk estimate allows effective evaluation of the impact of crosstalk within different connectors. The developed method can be effective for analyzing complex aircraft cable assemblies and connectors without requiring extensive knowledge of the assembly procedure.

Application of Emission Source Microscopy Technique to EMI Source Localization above 5 GHz

This paper presents the utilization of the emission source microscopy (ESM) technique to localize active sources of radiation on a PCB. For complex and large systems with multiple sources, localizing the sources of radiation often proves difficult. Near-field scanning provides limited information about the components contributing to far-field radiation. Two-dimensional synthetic aperture radar, a well-known technique used to diagnose and align phase array antennas, is adapted as emission source microscopy and utilized here for this alternative application. This paper presents the source localization methodology, along with simulation and measurement results. The results show that the proposed method can detect multiple active sources on a complex PCB.

The Impact of Near-Field Scanning Size on the Accuracy of Far-Field Estimation

The impact of near-field scanning sizes on the accuracy of far-field estimations is studied using a U-shape trace above a large ground plane as an example. Simulation model is built in commercial software and the planar near fields above the trace are obtained. Fourier Transform of the planar near fields is used to calculate the far-field radiations. Different sizes of planar scanning area are chosen and their corresponding computed far field patterns and maximum values are compared with those obtained by the software. It demonstrates that too small scanning size may lead to large errors in far-field calculations. Relationship between scanning plane height and planar scanning size is derived for accurate far field estimation, which is guidance for the extraction of accurate IC radiated emission model by planar near-field scanning technique.

Transfer Function Method for Predicting the Emissions in a CISPR-25 Test-Setup

The CISPR-25 standard is used in the automotive industry to characterize the electromagnetic radiation of electronic components. The setup is comprised of an electronic device, a cable harness, a metallic table, and an antenna. Dimensions stretch from a couple of meters for the setup to fractions of a millimeter for printed circuit board features. Numerical prediction of radiated emissions (RE) is of great usefulness for prediction of potential electromagnetic compatibility nonconformities in the early design process, but extremely difficult to be done for this setup as a whole. In this paper, we demonstrate how RE can efficiently be computed based on a setup as commonly used to model conducted emissions only, i.e., electric control unit and harness on infinite-ground plane. Applying Huygens principle and using it to generate a fixed transfer function between a particularly chosen Huygens surface and the antenna, we arrive at a novel computing scheme for RE. The scheme is applied for the antenna model and antenna factor-based calculations and demonstrates agreement with measurements within 5 dB range.

Nonlinear capacitors for ESD protection

In order to protect electronic products from Electrostatic Discharge (ESD) damage, multi-layer ceramic capacitors (MLCC) are often used to bypass the transient ESD energy. Most dielectric materials used in MLCC are nonlinear, since the dielectric constant decreases with increasing voltage, reducing the capacitance value, thus degrading the ESD protection effect. Using a large initial capacitance value will ensure sufficient ESD protection; however, the shunt capacitors also limit the signal bandwidth of the ESD-protected data channel, thus setting a maximal capacitance value at data voltage levels. This paper investigates the nonlinearity of capacitors and suggests improved tradeoff between ESD protection and data bandwidth by using the Antiferroelectric (AFE) capacitors as ESD protection. The dielectric constant of AFE material increases with increasing voltage. The voltage dependence of X7R and AFE capacitors are measured using static and nanosecond transient measurements. The ESD protection effectiveness with different material capacitors are compared by simulation. Due to very limited availability of suitable AFE material samples only hand-made capacitors have tested without investigating the long term stability of the material.

Phase-Resolved Near-Field Scan Over Random Fields

This letter discusses an averaging technique for phase-resolved scanning of the fields generated by multiple uncorrelated stochastic sources. This method can separate the field contribution of each noise source into the resulting field patterns as if the sources that are not of interest were turned off. The scanned data can be used to localize the emission sources and to calculate the far-field pattern and total radiated power.