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.

Improved target impedance and IC transient current measurement for power distribution network design

Abstract: An improved definition of target impedance is proposed in this paper, which is derived from the time-domain waveforms of the IC transient current and the allowable voltage fluctuation. The proposed target impedance removes the unnecessary constraint in the original definition and allows for more cost-effective power distribution network (PDN) designs for consumer electronic products. A measurement procedure to obtain IC transient current waveforms is also developed for the PDN designs utilizing power traces. The proposed target impedance and the measurement procedure have been validated using practical functioning designs.

Enhancing signal path characteristics in a circuit board

Abstract: A circuit board includes multiple signal layers, in which signal lines are routed, and power reference plane layers, in which power reference planes (e.g., power supply voltage or ground) are provided. Vias are passed through at least one signal layer and at least one power reference plane layer, or alternatively, vias are passed through at least two power reference plane layers. In one arrangement, a first clearance is defined around the via at the signal layer and a second clearance is defined around the via at the power reference plane layer. The second clearance is larger in size than the first clearance to match or tailor the impedance of the via as closely as possible with the impedance of the signal line that the via is electrically connected to. In another arrangement, clearances around vias at different power reference plane layers are selected to have different sizes to enhance the ability of one of the power reference plane layers (the one with a smaller clearance size) to carry a higher current level.

Modeling DC power-bus structures with vertical discontinuities using a circuit extraction approach based on a mixed-potential integral equation

Abstract: The DC power-bus is a critical aspect in high-speed digital circuit designs. A circuit extraction approach based on a mixed-potential integral equation is presented herein to model arbitrary multilayer power-bus structures with vertical discontinuities that include decoupling capacitor interconnects. Green's functions in a stratified medium are used and the problem is formulated using a mixed-potential integral equation approach. The final matrix equation is not solved, rather, an equivalent circuit model is extracted from the first-principles formulation. Agreement between modeling and measurements is good, and the utility of the approach is demonstrated for DC power-bus design.

Improving electromagnetic compatibility performance of packages and SiP modules using a conformal shielding solution

Abstract: High-speed digital and wireless devices radiate unintentional electromagnetic noise, which can affect the normal operation of other devices within the same system, causing intra-system electromagnetic interference (EMI) problems, or contribute to the total radiated EMI from the system, resulting in potential system-level EMI issues. PCB and system level shielding may alleviate the system-level EMI between wireless PCB board and the outside environment, but seldom prevent the intra-system EMI within the shielding enclosure. Package and System in Package (SiP) level shielding is desirable to shield the unintended radiation and protect the other circuits on board. Traditionally an external metal lid is employed to isolate the radiation from an IC, but the package cost and the size penalty due to the solder pads for shield attachment make the solution unattractive. In this paper, a new shielding technology for IC packages based on metal spray coating (conformal shielding) is presented. By spraying a conductive material on the sides of the package, a very thin metal layer is constructed around the top and four sides of a package. This very thin sprayed metal layer adds zero penalty to the package size and works similar to a solid metal shielding with very good shielding effectiveness; hence, it is suitable for wireless infrastructure, tele-communications, and high-speed digital applications.

Toward QoI and Energy Efficiency in Participatory Crowdsourcing

Abstract: Today's smartphones are also fundamentally transforming the traditional understanding of “crowdsourcing” to an emerging type of participatory task-oriented application. It aims to support the so-called “Citizen Science efforts” for knowledge discovery to understand human behavior and measure/evaluate their opinions. To facilitate these scenarios, in this paper, we propose a novel efficient network management framework for participatory crowdsourcing. Specifically, we first formulate the optimization problem and propose a closed-form optimal solution to meet the quality-of-information (QoI) requirements of the task while minimizing the energy consumption variance among participants. We then largely extend the traditional framework of Gur Game for distributed decision making to recommend different levels of information contribution for each participant by merging multiple automaton chains into a single chain with multiple steady states. By modeling the user bidding behaviors, we propose a few incentive-based participant selection schemes to maximize the platform's benefits and meet participants' expectations. We extensively evaluate the proposed schemes under the Massachusetts Institute of Technology (MIT) Social Evolution data set, where both QoI requirements of the request and credit saving are successfully achieved, with a satisfactory level of energy consumption fairness among participants.

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.