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.

Radio-frequency interference estimation by reciprocity theorem with noise source characterized by Huygens's equivalent model

Abstract: Noise coupling from a working IC to the neighboring victim antenna is estimated by decomposition based reciprocity theorem. The overall problem is decomposed into two parts. In the first part, the IC is turned on and the victim antenna is turned off, which is defined as forward problem. The second part is called reverse problem in which case the victim antenna is excited while the IC is turned off. An imaginary Huygens's box is introduced above the victim antenna for evaluating the coupled power from noise source to the victim RF antenna. The noise source is characterized by Huygens's equivalent source in the forward problem, and the victim antenna is modeled in full-wave simulation tool. With tangential E and H fields obtained in both forward problem and reverse problem, the coupled power can be estimated by numerical calculation of reciprocity theorem. The method by using Huygens's equivalent source is first validated by simulation in the forward problem. Later a test board with an IC and patch antenna is further measured to validate the overall methodology.

Identifying Interference From Multiple Noise Sources Using Only Magnetic Near Fields

Abstract: As electronic products become increasingly more complicated, multiple noise sources are likely to simultaneously interfere with the radio frequency (RF) receiver. It will be very helpful if the dominant noise source can be identified when solving the RF interference issue in a complex system. This article proposes a method to separately calculate the contributions from multiple noise sources at their overlapped frequencies so that the worse noise source could be identified even when multiple sources radiate simultaneously. The proposed method creatively employs the decomposition method based on the reciprocity theory to calculate the interference contribution from different sources. Furthermore, in the interest of reducing the near-field scanning time and complexity, the magnetic field only scanning method is developed by using the finite-element method (FEM). In the proposed method, Huygens's surface is established for each source. The tangential magnetic near fields on each Huygens's surface were then applied to solve the corresponding tangential electric fields by the FEM. Subsequently, the sources are removed while the corresponding Huygens's surfaces are maintained. The victim structure is excited under these conditions to obtain the tangential magnetic fields on Huygens's surfaces, and a novel FEM procedure is applied to obtain the tangential electric fields. Finally, based on the electric and magnetic fields, the interference from each noise source can be separately estimated based on the reciprocity theory. This method is validated by a numerical example and measurement. This approach can assist engineers in identifying the contribution of coupling from different sources and in efficiently resolving electromagnetic interference issues.

Reciprocity Theorem Based RFI Estimation for Heatsink Emission

Abstract: Heatsinks are widely used to dissipate heat in electronic devices. RF emission from heatsinks and ICs can cause radio frequency interference (RFI) issues. The existence of the heatsink affects the coupling from the noise source to the victim antenna. In this paper, the heatsink RFI problems are analyzed by two methods using reciprocity theorem. In the first method, the heatsink effect is combined with the antenna to derive the transfer function. In the second method, the heatsink can be characterized in both the source side and the antenna side on a closed 6-surface box. The physical insights and comparisons of the two RFI estimation methods based on reciprocity theorem will be investigated. The proposed methods will be utilized on a few numeric simulations for validations.

Control of Critical Coupling in a Coiled Coaxial Cable Resonator

Abstract: This paper reports a coiled coaxial cable resonator fabricated by cutting a slot in a spring-like coiled coaxial cable to produce a periodic perturbation. Electromagnetic coupling between two neighboring slots was observed. By manipulating the number of slots, critical coupling of the coiled coaxial cable resonator can be well controlled. An ultrahigh signal-to-noise ratio (over 50 dB) at the resonant frequency band was experimentally achieved from a coiled coaxial cable resonator with 38 turns. A theoretic model is developed to understand the device physics. The proposed device can be potentially used as a high quality and flexibly designed band-stop filter or a sensor in structural health monitoring.

DC ground compact wideband omnidirectional vertically polarised slot loop antenna for 4G long-term evolution applications

Abstract: A compact, wideband, omnidirectional, vertically polarised antenna without electrostatic discharge problems is proposed in this study for 4G long-term evolution applications. The proposed antenna is composed of three identical basic radiators separated by an angle of 120°. The basic radiator is based on a slot loop which is a wideband and DC ground structure. By bending the basic radiators, the antenna achieves better impedance matching and lower gain variation in the horizontal plane in a compact size. The proposed antenna reaches a fractional bandwidth of 45.5% for the voltage standing wave ratio (VSWR) <;1.5, a peak gain from 2.4 to 3.8 dBi with a gain ripple around 2 dB in the omnidirectional plane. It operates from 1700 to 2700 MHz, covering most 4G long-term evolution frequency bands. Both simulation and measurement of a prototype is done in this study to verify the antenna performance.

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.