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Passive Intermodulation Measurement:Challenges and Solutions

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Engineering 2022年第7期8卷 181-191页

作者： Zhanghua Cai Lie Liu Francesco de Paulis Yihong Qi general test systems inc. Shenzhen 518000China College of Electrical and Information Engineering Hunan UniversityChangsha 410082China UAq EMC Laboratory Department of Industrial and Information Engineering and EconomicsUniversity of L’AquilaL’Aquila 64100Italy

In modern wireless communication systems,the signal-to-noise ratio(SNR)is one of the most important performance *** the other radio frequency(RF)performance of the components is well designed,passive intermodulation(PIM)interference may become an important factor limiting the system’s *** it is a base station,an indoor distributed antenna system,or a satellite system,there are stringent PIM level requirements to minimize interference and enhance network capacity in multicarrier *** for systems of high power and wide bandwidth such as 5G wireless communication,PIM interference is even more *** to the complexity and uncertainty of PIM,measurement is the most important means to study and evaluate the PIM performance of wireless communication *** this review,the current main PIM measurement methods recommended by International Electrotechnical Commission(IEC)and other standard organizations are introduced,and several key challenges in PIM measurement and their solutions(including the design of PIM tester,the location of the PIM sources,the design of compact PIM anechoic chambers,and the evaluation methods of PIM anechoic chambers)are *** challenges are of great significance to solve PIM problems that may arise during device characterization and verification in real wireless communication systems.

关键词： Passive intermodulation(PIM) PIM source location Anechoic chamber

A 2×2 MIMO Throughput Analytical Model for RF Front End Optimization

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Journal of Communications and Information Networks 2020年第2期5卷 194-203页

作者： Penghui Shen Yihong Qi Xianbin Wang Wei Zhang Wei Yu College of Electric and Information Hunan UniversityChangsha 410082China general test systems inc. Shenzhen 518000China Cheng Laboratory Shenzhen 518000China Department of Electrical and Computer Engineering Western UniversityLondonON N6A 5B9Canada School of Electrical Engineering and Telecommunications University of New South WalesSydney NSW 2052Australia

With a given communication protocol,performance optimization of a multiple-input multipleoutput(MIMO)wireless system mainly lies on the design of the radio frequency(RF)front ***,the optimization is mainly achieved based on experiences,such as promoting the multiple antenna gains and reducing their *** experience-based method works to a certain extent,but is inefficient since the final performance impact by each sub-system is not *** challenge lies on how to find the most limiting factor that restricts the overall communication *** paper presents an analytical model for throughput calculations of 2×2 MIMO wireless system,which is built on a first step of maximum rate calculated under the chosen protocol and channel,followed by a second step of throughput baseline measurement,and continued with the third step of throughput calculations of the overall system according to the actual settings of *** model can provide a detailed diagnostic report of each RF factor,which will directly point out the imperfections and make the troubleshooting and debugging much more ***,throughput is analyzed in a mathematical approach that allows the performance more predictable during the design phase.

关键词： throughput analytical model MIMO RF performance optimizations

From intrinsic dielectric loss to geometry patterns: Dual-principles strategy for ultrabroad band microwave absorption

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Nano Research 2021年第5期14卷 1495-1501页

作者： Bin Quan Weihua Gu Jiaqi Sheng Xinfeng Lv Yuyi Mao Lie Liu Xiaogu Huang Zongjun Tian Guangbin Ji College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing210016China School of Chemistry and Materials Science Nanjing University of Information Science&TechnologyNanjing210044China National Center of Supervision and Inspection on Additive Manufacturing Products Quality Wuxi214000China shenzhen general test systems inc Taohuayuan Hi-Tech ParkShenzhen518102China College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing210016China

As electromagnetic absorbers with wide absorption bandwidth are highly pursued in the cutting-edge electronic and telecommunication industries, the traditional dielectric or magnetic bulky absorbers remain concerns of extending the effective absorption bandwidth. In this work, a dual-principle strategy has been proposed to make a better understanding of the impact of utilizing conductive absorption fillers coupled with implementing artificial structures design on the absorption performance. In the comparison based on the microscopic studies, the carbon nanotubes (CNTs)-based absorbers are confined to narrow operating bandwidth and relatively fixed response frequency range, which can not fulfill the ever-growing demands in the application. With subsequent macroscopic structure design based on the CNTs-based dielectric fillers, the artificial patterns show much more broadened absorption bandwidth, covering the majority of C-band, the whole X-band, and Ku-band, due to the tailored electromagnetic parameters and more reflections and scatterings. The results suggest that the combination of developing microscopic powder/bulky absorbers and macroscopic configuration design will fundamentally extend the effective operating bandwidth of microwave.

关键词： geometry patterns numerical simulation three-dimensional(3D)printing broadband microwave absorption

Over-the-air measurement for MIMO systems

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Frontiers of Information Technology & Electronic Engineering 2021年第8期22卷 1046-1058页

作者： Jun LI Yihong QI Jun FAN College of Electrical and Information Engineering Hunan UniversityChangsha 410082China general test systems inc. Shenzhen 518054China Department of Research and Development Peng Cheng LaboratoryShenzhen 518000China Department of Research and Development LinkE Technologies(Hengqin)Zhuhai 519030China

Over-the-air(OTA)testing is an industry standard practice for evaluating transceiver performance in wireless *** the fifth generation(5G)and beyond wireless systems with high integration,OTA testing is probably the only reliable method to accurately measure the transceiver performance,suitable for certification as well as for providing feedback for design verification and ***,multiple-input multiple-output(MIMO)technology is extensively applied for stable connection,high throughput rate,and low *** this paper,we provide an overview of the three main methods for evaluating the MIMO OTA performance,namely,the multiprobe anechoic chamber(MPAC)method,the reverberation chamber plus channel emulator(RC+CE)method,and the radiated two-stage(RTS)method,with the aim of providing a useful guideline for developing effective wireless performance testing in future 5G-and-beyond wireless systems.

关键词： Over-the-air(OTA)testing Wireless performance testing Fifth generation(5G)and beyond Multiple-input multiple-output(MIMO) Multiprobe anechoic chamber(MPAC) Radiated two-stage(RTS) Reverberation chamber plus channel emulator(RC+CE)

Improvement of decentralized random decrement technique for data processing in wireless sensor network

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Earthquake Engineering and Engineering Vibration 2016年第3期15卷 627-635页

作者： Liu Chengyin Xu Chunchuan Teng Jun School of Civil and Environmental Engineering Harbin Institute of Technology Shenzhen Graduate School Underground systems Inc. 84 Business Park DriveArmonk

The Random Decrement Technique （RDT）, based on decentralized computing approaches implemented in wireless sensor networks （WSNs）, has shown advantages for modal parameter and data aggregation identification. However, previous studies of RDT-based approaches from ambient vibration data are based on the assumption of a broad-band stochastic process input excitation. The process normally is modeled by filtered white or white noise. In addition, the choice of the triggering condition in RDT is closely related to data communication. In this project, research has been conducted to study the nonstationary white noise excitations as the input to verify the random decrement technique. A local extremum triggering condition is chosen and implemented for the purpose of minimum data communication in a RDT-based distributed computing strategy. Numerical simulation results show that the proposed technique is capable of minimizing the amount of data transmitted over the network with accuracy in modal parameters identification.

关键词： RDT decentralized computing wireless sensor networks nonstationary

Rapid processing of ferrite ceramics with promising magneto-dielectric characteristics

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Journal of Advanced Dielectrics 2017年第6期7卷 42-47页

作者： Zhuohao Xiao Chuanhu Wang Lie Liu Zhihong Yang Ling Bing Kong School of Materials Science and Engineering Jingdezhen Ceramic Institute Jingdezhen 333001 P.R.China School of Materials Science and Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Department of Material and Chemical Engineering Bengbu University Bengbu 233030AnhuiP.R.China general test systems inc.shenzhen 518102GuangdongP.R.China College of Materials Science and Technology Nanjing University of Aeronautics and Astronautics Nanjing 211100 P.R.China

Ferrite ceramics,Ni_(0.88)Zn_(0.07)Co_(0.05)Fe_(1.98)O_(4),with the addition of 4 wt.%Bi_(2)O_(3) as sintering aid,were fabricated by using a simple one-step processing without involving the step of calcination.X-ray diffraction(XRD)results indicated that single phase ferrite ceramics can be achieved after sintering at 1000℃ for 2 *** samples demonstrated relative densities in the range of 97-99%.Desired magneto-dielectric properties have been approached by adjusting the sintering temperature and sintering time *** technique is believed to be applicable to other ceramic materials.

关键词： Ferrite dielectric property magnetic property magneto-dielectric

Bioinspired Spiral Soft Pneumatic Actuator and Its Characterization

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Journal of Bionic Engineering 2021年第5期18卷 1101-1116页

作者： Zhiyuan Zhang Xueqian Wang Deshan Meng Bin Liang shenzhen Key Laboratory of Intelligent Robotics Tsinghua Shenzhen International Graduate SchoolShenzhen 518055China Institute of Robotics and Intelligent systems ETH Zurich8801 ZurichSwitzerland Research Institute of Tsinghua University at shenzhen Shenzhen 518057China School of Aeronautics and Astronautics Sun Yat-Sen UniversityShenzhen 518107China

Soft robots have unique advantages over traditional rigid robots and have broad application prospects in many *** expand their bioinspired applications,we propose a novel Soft Pneumatic Actuator(SPA)associated with spiral configuration inspired by the structure and unwinding motion of the seahorse *** erent from bending motion of common soft actuators,the spiral SPA can generate unwinding motion as input air pressure ***,to explore the eff ect of diff erent initial spiral types on unwinding performance,three typical spiral SPAs are designed and simulated while keeping the outside arc of actuator body ***,a static model of the spiral SPA is established by combining the hyperelastic material model,geometric relationships,and virtual work *** improve model accuracy,two geometric correction parameters are employed and their physical significance is analyzed by finite element ***,a prototype of the logarithmic spiral SPA(Log_spiral SPA)is fabricated and a Fiber Bragg Grating(FBG)sensor array is designed to detect and reconstruct unwinding shapes of the ***,the unwinding performance,static model and output force capability of the prototype are tested and ***,we discuss prospects for this novel spiral SPA and test its practical applications in inchworm-like motion,assisting finger rehabilitation and object capture.

关键词： Soft robotics Spiral Soft actuator Virtual work principle Fiber Bragg grating

The influence of an Si_xN_y interlayer on a GaN film grown on an Si(111) substrate

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Chinese Physics B 2012年第12期21卷 494-498页

作者：彭冬生陈志刚谭聪聪 Key Laboratory of Optoelectronic Devices and systems of Ministry of Education and Guangdong Province Shenzhen University

A method to drastically reduce dislocation density in a GaN film grown on an Si（111） substrate is newly developed. In this method, the SixNy interlayer which is deposited on an A1N buffer layer in situ is introduced to grow the GaN film laterally. The crack-free GaN film with thickness over 1.7 micron is successfully grown on an Si（lll） substrate. A synthesized GaN epilayer is characterized by X-ray diffraction （XRD）, atomic force microscope （AFM）, and Raman spectrum. The test results show that the GaN crystal reveals a wurtzite structure with the （0001） crystal orientation and the full width at half maximum of the X-ray diffraction curve in the （0002） plane is as low as 403 arcsec for the GaN film grown on the Si substrate with an SixNy interlayer. In addition, Raman scattering is used to study the stress in the sample. The results indicate that the SizNy interlayer can more effectively accommodate the strain energy. So the dislocation density can be reduced drastically, and the crystal quality of GaN film can be greatly improved by introducing an SixNy interlayer.

关键词： SixNy interlayer silicon substrate GaN film Raman scattering

Flashover Characteristics of Dry Band-water band on Hydrophobic Surfaces

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CSEE Journal of Power and Energy systems 2024年第1期10卷 392-400页

作者： Xiaohan Wu Fanghui Yin Bin Cao Daiming Yang Shichao Shao Liming Wang Tsinghua-Berkeley shenzhen Institute(TBSI) Shenzhen 518055China shenzhen International Graduate School Tsinghua UniversityShenzhen 518055China shenzhen Polytechnic School Shenzhen 518055China

Due to their outstanding anti-flashover characteristics,composite insulators have been extensively applied in power systems.A lot of research has investigated flashover characteristics of hydrophobic specimens with artificial water ***,the phenomenon is not consistent with that of the contaminated composite *** the test specimens covered with water droplets,there is no obvious leakage current before the flashover and no obvious relationship between flashover voltage and the conductivity of water *** the contaminated composite insulator surface,there are short continuous arcs on the insulators before critical flashover,making insulators look like a luminous *** that under these two conditions,the proportion of water along the insulation distance is different,the flashover characteristic of“dry band-water band”on a hydrophobicity surface is analyzed in the present *** influence of the water band parameter(including length,width,and conductivity)as well as the length of dry band is *** this basis,the arc generation and development process of the surface covered with“dry band-water band”is *** research results improve the understanding of the flashover process on contaminated composite insulators.

关键词： Flashover characteristics hydrophobicity partial arc water band