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.

Extracting characteristic impedance of a transmission line referenced to a meshed ground plane

Abstract: Meshed power and ground planes are commonly used in today's flexible printed circuit board (PCB). In this paper, a methodology to extract the effective characteristic impedance as well as the per-unit-length parameters of a transmission line with a meshed reference plane is proposed based on an equivalent transmission line model. The validity of this methodology is confirmed through comparison with full-wave simulations.

Calibration Loop Antenna for Multiple Probe Antenna Measurement System

Abstract: In order to achieve high accuracy in measurements of the multiple probe antenna measurement system (MPAMS), an omnidirectional calibration antenna with a small gain variation in the horizontal polarization (named calibration loop antenna, in convention) is required. This article presents such an antenna design. The proposed calibration loop antenna consists of four arc-folded dipoles with dimensions of 52 mm $\times52$ mm $\times 1$ mm, balun structures for suppressing common mode current, and four parasitic strips for impedance matching on each of the top and bottom planes. The experimental results show that the proposed calibration loop antenna has a small gain variation in the horizontal polarization less than 0.16 dB in a bandwidth of 20% (2.25–2.75 GHz), and its 10-dB return loss bandwidth is 18.2%. Also, the cross-polarization ratio in the operating bandwidth is greater than 24 dB. Along with the desired omnidirectional radiation pattern, the low profile and compact design further make the proposed calibration loop antenna a suitable selection for calibration in MPAMS.

Including SMT ferrite beads in DC power bus and high-speed I/O line modeling

Abstract: Surface mount technology (SMT) ferrite beads are often used in high-speed digital circuit designs to mitigate noise. The common modeling approach is to include SMT ferrite beads as equivalent lumped LCR circuits. The work presented in this paper included SMT ferrite beads as a frequency-dependent impedance in a PEEC-like modeling tool denoted CEMPIE, a circuit extraction approach based on a mixed-potential integral equation formulation. Agreement with measurements demonstrates the approach. The applications shown are segmentation of power areas for noise isolation, and I/O line filtering.

Investigation of crosstalk among vias

Abstract: Crosstalk among vias is a critical problem in high-speed digital circuits, deteriorating signal quality and increasing jitter, especially when circuit density is high. Underlying mechanism of crosstalk among vias is investigated in this paper. Using a physics-based equivalent circuit model, crosstalk as a function of various geometrical parameters, including parallel plane pair thickness, layer count in printed circuit board (PCB) stackup, ground via patterns, and parallel plane pair dimensions, has been investigated. A multi-step crosstalk evaluation procedure is proposed based on the study for PCB layout-design verifications.

EMI reduction evaluation with flexible absorbing materials and ferrite cores applied on cables

Abstract: Cables, represented by monopole antennas and coated with magneto-dielectric absorbing materials or containing ferrite cores, can be used to estimate how much electromagnetic interference (EMI) reduction the corresponding coatings cause. Two-dimensional finite element method (2D-FEM) has been developed to calculate the EMI reduction by taking advantage of the axial symmetry of the geometry. A standard technique based on the 7/3-mm coaxial air line and vector network analyzer measurements is used to extract the relative permeability and permittivity of the flexible absorbing materials or ferrites. With the extracted parameters, both the input impedance and the EMI reduction on cables coated with absorbing materials or containing a ferrite choke can be calculated by the 2D-FEM, and the input impedance is also compared with the experiment result. At last, EMI reduction values of absorbing sheet material and ferrite are evaluated by 2DFEM based on realist geometry of cables.

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.