Jun Fan

Bio: Jun Fan is an academic researcher from Missouri University of Science and Technology. The author has contributed to research in topics: Equivalent circuit & Printed circuit board. The author has an hindex of 36, co-authored 482 publications receiving 5641 citations. Previous affiliations of Jun Fan include Ulsan National Institute of Science and Technology & University of Missouri.

Improvements in GMI probe design for time-domain transient current measurements

Abstract: Measurement techniques for time-domain transient currents are widely needed in many EMC applications. Demonstrated to have a lot of potential for this purpose, giant magnetio-impedance (GMI) probes are studied in this paper. Improvements in the probe design, including a balanced circuit for increased signal to noise ratio and an on-probe magnetic-field bias circuit, are proposed. These improvements in the probe design make the GMI probes more suitable for practical applications of time-domain transient current measurements.

Cable Harness Modeling Using MTL Parameters Derived from Integral Equations

Abstract: A method to calculate equivalent Multiconductor Transmission-Line (MTL) parameters through integral equations is proposed in this paper. In the mixed-potential integral equations (MPIE), the elements of harness part are converted to MTL parameters based on the relations between MTL parameters and partial elements of 1-D wire segments. Then, to include the effects of reference metal plane nearby, the equivalent MTL parameters can be derived from the MPIE equations with modified harness elements by keeping the solutions on harness part the same. The current distributions on wires calculated using the equivalent MTL parameters have good correlations with the results from the original MPIE solver, and the understanding on the behavior of cable harness routing over nonideal reference plane can be analyzed in more detail and accurately with the extracted equivalent MTL parameters.

Providing shields for systems

Abstract: A supplemental shield is used to cover a radiation leakage path through a chassis of the system. The supplemental shield is attached to at least one surface in the system to cover the radiation leakage path. In one arrangement, the supplemental shield has an adhesive portion to attach the supplemental shield to the at least one surface.

Estimating Electromagnetic Emissions from a Site Installation with Multiple Racks of Server Equipment

Abstract: More than hundreds, sometimes even thousands, of servers operate simultaneously inside a data center. Their radiation can be a problem and cause electromagnetic interference (EMI) issues. However, it is not feasible to perform full-wave 3D simulation of these racks because of the large electrical size of the model. In this paper, an algorithm is proposed to predict the emission from rack arrays. The equivalent dipole source is extracted from EMI measurement data of a single rack and reconstructed as a radiation source in a multiple rack model. The racks in an array can be divided into a few categories and the racks in each category have similar radiation patterns. Thus only one modeling of a representative rack is needed for each category. In order to take rack to rack scattering into consideration, a simplified model for each category is developed and method of moments is used to describe the radiation of representative racks. After the radiation calculations from a representative rack in all the categories are completed, the total radiation from the data center is predicted based on these representative-rack calculations. This method is much faster than the brute-force simulation of the entire data center, and is highly scalable to handle arbitrary number of racks in the data center.

Far-End Crosstalk Modeling and Prediction for Stripline With Inhomogeneous Dielectric Layers (IDLs)

Abstract: Far-end crosstalk (FEXT) is a critical factor that limits signal integrity performance in high-speed systems. The FEXT level is sensitive to the dielectric inhomogeneity of the stripline in fabricated printed circuit boards (PCBs). The dielectric of the stripline is manufactured with multiple inhomogeneous dielectric layers (IDLs) of various resin and glass fiber bundles. A marginal difference in the dielectric permittivity of the IDLs can lead to a significant change FEXT level. In this article, a practical FEXT modeling methodology for striplines is proposed by introducing the extraction method for ${{\boldsymbol{\varepsilon }}}_{\boldsymbol{r}}$ of IDLs. The new stripline model is constructed with three IDLs comprised of core, prepreg, and resin pocket, to improve the model accuracy. With the cross-sectional geometry and measured S-parameters of the coupled striplines, ${{\boldsymbol{\varepsilon }}}_{\boldsymbol{r}}$ of IDLs can be extracted. In addition, an analytical model to predict the FEXT polarity and magnitude of the stripline caused by the inhomogeneity is proposed targeted for prelayout application. The proposed models have been verified using measurement. The proposed models can provide useful analysis methodology and design guidelines to mitigate the FEXT level in high-speed systems, especially for high-volume PCB tests in the prelayout and postlayout stages.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

IEEE Transactions on Microwave Theory and Techniques and Antennas and Propagation Announce a Joint Special Issue on Ultra-Wideband (UWB) Technology

Abstract: Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.