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.

Coaxial Cable Bragg Grating Sensors for Large Strain Measurement

Abstract: In this paper, a new coaxial cable Bragg grating (CCBG) is developed as a strain sensor and the sensor's capacity for large range strain measurement in structural health monitoring (SHM) is demonstrated for the first time. The sensor device is comprised of regularly spaced periodic discontinuities along a coaxial cable. The discontinuities are fabricated using a computer numerical controlled (CNC) machine to drill holes in the cable. Each discontinuity generates a weak reflection to the electromagnetic wave propagating inside the cable. Superposition of these weak reflections produces a strong reflection at discrete frequencies that can be explained by Bragg grating theory. By monitoring the resonant frequency shift of the sensor's reflection or transmission spectra, strain measurement sensitivity of 20μe and a dynamic range of 50000μe (5%) were demonstrated for axial strain measurements. The experimental results show that the CCBG sensors perform well for large strain measurement needed in structural health monitoring (SHM).

Study of Thickening Soldermask Coated Microstrip Lines on High-Speed PCBs for Crosstalk Reduction in DDR5

Abstract: Far-end crosstalk (FEXT) is one major factor impacting performance of DDR signals on printed circuit board (PCB) external layers (microstrip routing). Bigger spacing can help reduce FEXT. However, as there are lots of DDR signals, in most cases, there is little room to increase spacing. In this paper, we develop a simple and efficient DDR5 crosstalk reduction approach by using thickening soldermask coated microstrip lines (TSCMLs). The type of soldermask is regular low-loss material, which is mainly used for resistance welding transform. The simulated results show the achieved FEXT can maintain under −36.0 dB from dc to 16 GHz, and 23 dB reduction in FEXT is achieved at 3.2GHz in comparison with the initial microstrip lines. The measured results show that the peak FEXT voltage can be decreased by 83% of that without thickening soldermask. The experimental results are in agreement with the simulation and both validate the proposed design.

Tunable Intermodulation Generator for Passive Intermodulation Tester Calibration

Abstract: As a key step to guarantee passive intermodulation (PIM) test accuracy, PIM calibration for PIM tester draws great attention these days. This paper provides three solutions to realize tunable PIM calibration standard sources for PIM tester calibration. Two types of nonlinearity sources are applied while three circuit or cavity structures are developed to control these sources. By using different strategies, the proposed PIM sources can generate controllable PIM references with different ranges that cover most PIM test ranges. In the experiments, the PIM signal stability is evaluated as well as PIM dynamic range. They show the minimal PIM fluctuation as less as 1dB, while the maximal dynamic range can reach 50dB. As these solutions have various sizes and function, they can be utilized according to different test requirements and easily integrated with PIM tester. These solutions can help develop new generation of PIM testers.

FEXT Reduction Using Mushroom Structures Thickened Soldermask for DDR5 PCBs

Abstract: Far-end crosstalk (FEXT) between adjacent signal lines is one of the most critical factors affecting signal integrity (SI) in double data rate 5 (DDR5) printed circuit boards (PCBs). In this paper, a new method for FEXT reduction, based on mushroom structures thickened soldermask (MSTS) for coupled signal lines, is proposed and investigated. From the simulated S-parameters results, FEXT of this proposed method can be suppressed among a very wide frequency range. Additionally, the FEXT is decreased more than 25dB around the main frequency of DDR5, compared with the traditional signal routing. Finally, both frequency and time domains results show that our proposed method could significantly improve the performance of SI and dramatically reduce FEXT for DDR5 system designs.

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.