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.

Empirical Modeling of Contact Intermodulation Effect on Coaxial Connectors

Abstract: An empirical modeling of contact nonlinearity-induced intermodulation (IM) effect on the coaxial connector is presented in this article. The IM weights on inner and outer conductors are clarified using the measurement method. The contact degeneration-induced IM evolution is quantized by considering the contact coupling effect between the inner and outer conductors. This article demonstrated a set of test methods to quantify the oxide-induced nonlinearity with contact degeneration effects, and these methods can evaluate the contact IM products and further predict the low IM lifetime of passive devices.

Validating the transmission-line based material property extraction procedure including surface roughness for multilayer PCBs using simulations

Abstract: Accurate frequency-dependent dielectric properties are important for accurate modeling of signal and power integrity problems. One method for extracting dielectric properties from fabricated multilayer printed circuit boards is based on the measured electrical property of fabricated transmission lines, denoted the “Root-omega” method. In this paper, the “Root-omega” method applied to the cases with smooth and rough conductors is validated using simulations. Potential errors in the procedure are discussed.

Impedance of an infinitely large parallel-plane pair and its applications in engineering modeling

Abstract: In this paper, a closed-form expression for the impedance of an infinitely large parallel plane pair is presented. It is applicable to practical printed circuit board (PCB) design problems where there are multiple shorting vias around the signal vias of interest. With the presence of multiple shorting vias, reflections from the plane pair edges can be neglected since the shorting vias prevent the electromagnetic energy from leaking away from the local cavity around the signal vias. The self and transfer impedance expressions can be obtained using the expansion of cylindrical waves. The impedances calculated from both the rectangular cavity model and the infinitely large plane pair model for several design examples are compared to demonstrate the effectiveness of the infinite plane pair approximation.

Desense Prediction and Mitigation from DDR Noise Source

Abstract: Ahstract- In this paper, the dipole-moment based reciprocity method is used to perform desense prediction and mitigation from the DDR noise source to the nearby RF antenna. The noise source is from the DDR signals between the application processor and the memory IC. Radiation physics of the noise source is analyzed by understanding of the current flow. Firstly, the random nature of the DDR signals is analyzed using the measurement data. Based on the measurement data, the setup of the near field scanning is further determined. The desense prediction procedures are decomposed into two steps: the forward problem and the reverse problem. In the forward problem, the noise source is approximately regarded as a single magnetic dipole moment based on the near field scanning above this specific electronic device. In the reverse problem, the transfer function from the magnetic dipole moment to the victim antenna is obtained by measuring the H field when the victim antenna radiates. Based on the measurements of forward and reverse problem, the coupled noise to the victim antenna can be analytically estimated. The estimated RFI results are compared with direct RFI measurement to validate the dipole-moment based reciprocity method. Lastly, a few methods to mitigate the desense are also discussed.

EMI Coupling Paths and Mitigation in a Board-to-Board Connector

Abstract: Cage connectors for optical subassembly I/O modules have been identified as one of the main coupling paths in an optical link at the front-end of switches and routers. In the study presented herein, the simulation model used to study electromagnetic interference coupling physics and mitigation of the optical cage connector was corroborated by comparing the measured and simulated results for the total radiated power (TRP). Currents on the adjacent ground references to the differential signal conductors caused half-wave resonant peaks in the TRP response in the frequency range of 4–18 GHz. At frequencies from 18 to 28 GHz, both full-wave simulation and analytical formulas indicate that the radiation results primarily from the currents on the signal traces. The radiation from the optical cage connector was suppressed with absorbing materials, and the coupling path was verified, together with the optical cage and module enclosure.

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.