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1. A Practical Distributed ADMM Solver for Billion-Scale Generalized Assignment Problems

Author

Zhou, Jun, Qi, Feng, Hua, Zhigang, Jian, Daohong, Liu, Ziqi, Wu, Hua, Zhang, Xingwen, and Yang, Shuang

Subjects
Computer Science - Data Structures and Algorithms
Abstract

Assigning items to owners is a common problem found in various real-world applications, for example, audience-channel matching in marketing campaigns, borrower-lender matching in loan management, and shopper-merchant matching in e-commerce. Given an objective and multiple constraints, an assignment problem can be formulated as a constrained optimization problem. Such assignment problems are usually NP-hard, so when the number of items or the number of owners is large, solving for exact solutions becomes challenging. In this paper, we are interested in solving constrained assignment problems with hundreds of millions of items. Thus, with just tens of owners, the number of decision variables is at billion-scale. This scale is usually seen in the internet industry, which makes decisions for large groups of users. We relax the possible integer constraint, and formulate a general optimization problem that covers commonly seen assignment problems. Its objective function is convex. Its constraints are either linear, or convex and separable by items. We study to solve our generalized assignment problems in the Bregman Alternating Direction Method of Multipliers (BADMM) framework where we exploit Bregman divergence to transform the Augmented Lagrangian into a separable form, and solve many subproblems in parallel. The entire solution can thus be implemented using a MapReduce-style distributed computation framework. We present experiment results on both synthetic and real-world datasets to verify its accuracy and scalability.

Published
2022

4. Daily point-of-care ultrasound-assessment of central venous catheter-related thrombosis in critically ill patients: a prospective multicenter study

Author

Wu, Chunshuang, Zhang, Mao, Gu, Wenjie, Wang, Caimu, Zheng, Xudong, Zhang, Junfeng, and Zhang, Xingwen

Subjects
Medical research -- Health aspects, Medicine, Experimental -- Health aspects, Catheterization -- Health aspects, Blood clot -- Health aspects, Thrombosis -- Health aspects, Health care industry
Abstract

Purpose Central venous catheter (CVC)-related thrombosis (CRT) is a known complication in critically ill patients. However, its clinical significance remains unclear. The objective of the study was to evaluate the occurrence and evolution of CRT from CVC insertion to removal. Methods A prospective multicenter study was conducted in 28 intensive care units (ICUs). Duplex ultrasound was performed daily from CVC insertion until at least 3 days after CVC removal or before patient discharge from the ICU to detect CRT and to follow its progression. CRT diameter and length were measured and diameter > 7 mm was considered extensive. Results The study included 1262 patients. The incidence of CRT was 16.9% (95% confidence interval 14.8-18.9%). CRT was most commonly found in the internal jugular vein. The median time from CVC insertion to CRT onset was 4 (2-7) days, and 12% of CRTs occurred on the first day and 82% within 7 days of CVC insertion. CRT diameters > 5 mm and > 7 mm were found in 48% and 30% of thromboses. Over a 7-day follow-up, CRT diameter remained stable when the CVC was in place, whereas it gradually decreased after CVC removal. The ICU length of stay was longer in patients with CRT than in those without CRT, and the mortality was not different. Conclusion CRT is a frequent complication. It can occur as soon as the CVC is placed and mostly during the first week following catheterization. Half of the thromboses are small but one-third are extensive. They are often non-progressive and may be resolved after CVC removal., Author(s): Chunshuang Wu [sup.1] [sup.2] [sup.3], Mao Zhang [sup.1] [sup.2] [sup.3], Wenjie Gu [sup.1] [sup.2] [sup.3], Caimu Wang [sup.4], Xudong Zheng [sup.5], Junfeng Zhang [sup.6], Xingwen Zhang [sup.7], Shijin Lv [...]

Published
2023
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5. Learning (Re-)Starting Solutions for Vehicle Routing Problems

Author

Zhang, Xingwen and Yang, Shuang

Subjects
Computer Science - Artificial Intelligence, Computer Science - Machine Learning
Abstract

A key challenge in solving a combinatorial optimization problem is how to guide the agent (i.e., solver) to efficiently explore the enormous search space. Conventional approaches often rely on enumeration (e.g., exhaustive, random, or tabu search) or have to restrict the exploration to rather limited regions (e.g., a single path as in iterative algorithms). In this paper, we show it is possible to use machine learning to speedup the exploration. In particular, a value network is trained to evaluate solution candidates, which provides a useful structure (i.e., an approximate value surface) over the search space; this value network is then used to screen solutions to help a black-box optimization agent to initialize or restart so as to navigate through the search space towards desirable solutions. Experiments demonstrate that the proposed ``Learn to Restart'' algorithm achieves promising results in solving Capacitated Vehicle Routing Problems (CVRPs).

Published
2020

6. Solving Billion-Scale Knapsack Problems

Author

Zhang, Xingwen, Qi, Feng, Hua, Zhigang, and Yang, Shuang

Subjects
Computer Science - Distributed, Parallel, and Cluster Computing, Computer Science - Artificial Intelligence, Computer Science - Data Structures and Algorithms
Abstract

Knapsack problems (KPs) are common in industry, but solving KPs is known to be NP-hard and has been tractable only at a relatively small scale. This paper examines KPs in a slightly generalized form and shows that they can be solved nearly optimally at scale via distributed algorithms. The proposed approach can be implemented fairly easily with off-the-shelf distributed computing frameworks (e.g. MPI, Hadoop, Spark). As an example, our implementation leads to one of the most efficient KP solvers known to date -- capable to solve KPs at an unprecedented scale (e.g., KPs with 1 billion decision variables and 1 billion constraints can be solved within 1 hour). The system has been deployed to production and called on a daily basis, yielding significant business impacts at Ant Financial.

Published
2020

9. On the Relationship Between the OpenAI Evolution Strategy and Stochastic Gradient Descent

Author

Zhang, Xingwen, Clune, Jeff, and Stanley, Kenneth O.

Subjects
Computer Science - Neural and Evolutionary Computing
Abstract

Because stochastic gradient descent (SGD) has shown promise optimizing neural networks with millions of parameters and few if any alternatives are known to exist, it has moved to the heart of leading approaches to reinforcement learning (RL). For that reason, the recent result from OpenAI showing that a particular kind of evolution strategy (ES) can rival the performance of SGD-based deep RL methods with large neural networks provoked surprise. This result is difficult to interpret in part because of the lingering ambiguity on how ES actually relates to SGD. The aim of this paper is to significantly reduce this ambiguity through a series of MNIST-based experiments designed to uncover their relationship. As a simple supervised problem without domain noise (unlike in most RL), MNIST makes it possible (1) to measure the correlation between gradients computed by ES and SGD and (2) then to develop an SGD-based proxy that accurately predicts the performance of different ES population sizes. These innovations give a new level of insight into the real capabilities of ES, and lead also to some unconventional means for applying ES to supervised problems that shed further light on its differences from SGD. Incorporating these lessons, the paper concludes by demonstrating that ES can achieve 99% accuracy on MNIST, a number higher than any previously published result for any evolutionary method. While not by any means suggesting that ES should substitute for SGD in supervised learning, the suite of experiments herein enables more informed decisions on the application of ES within RL and other paradigms.

Published
2017

11. Effects of Silicon Formulations on Cold Tolerance of Rice Seedlings.

Author

Ren Hongyu, Wang Wenbo, Li Xuecong, Li Shuai, Wen Yahuan, and Zhang Xingwen

Subjects
EFFECT of silicon on plants, RICE, COLD-tolerant plants
Abstract

To investigate the effects of silicon formulations on the cold tolerance of rice seedlings, Song Japonica 16 (not cold tolerant) and Dongnong 427 (cold tolerant) rice varieties were used as test materials and four different types of silicon formulations, Si-50-G, Si-60-G, Si-T-G, and Si-E-G, were applied as foliar sprays at the seedling stage, and a control group CK (equal amount of distilled water) was set up. One week after the first silicon spray, two types of rice were subjected to low-temperature stress treatments at day/night temperatures of 12 °C/10 °C for 2, 4, 6, and 8 days. The effects of different silicon formulations on the chlorophyll, proline (Pro) and soluble sugar contents as well as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities of rice seedlings under low-temperature stress were compared to find out the effects of silicon formulations on the cold tolerance of rice seedlings. The results showed that silicon formulations could significantly increase the chlorophyll content of rice seedling leaves, with Si-50-G being the most effective, with a significant increment of 40.17% compared to the CK at 2 days of low temperature. Four silicon formulations significantly increased the proline content and soluble sugar content of rice leaves at low temperature for 4-8 days. For Song Japonica 16, the most significant increment in leaf POD activity was observed in Si-E-G treatment at 2, 4 and 8 days of temperature stress, with 73.58%, 20.95% and 217.24% increases compared to the CK, respectively. For 4 and 6 days of temperature stress, the most significant increase in CAT activity was observed in Si-E-G treatment, with 25.70% and 75.78% increases compared to the CK, respectively. For Dongnong 427, the Si-60-G treatment showed the highest increase in leaf SOD activity for 4 and 8 days of temperature stress, with significant increases of 58.15% and 82.76% compared to the CK, respectively, and the Si-E-G treatment showed the highest increase in leaf POD activity for 2 and 8 days of temperature stress, with significant increases of 97.75% and 245.10% compared to the CK, respectively. It showed that the spraying of silicon formulations could significantly enhance the cold tolerance of rice. This study provided a scientific basis for the rational use of silicon formulations to enhance cold tolerance in rice and had important theoretical and practical significance for ensuring sustainable high and stable rice yields in Heilongjiang Province, as well as for the development of silicon fertilizers. [ABSTRACT FROM AUTHOR]

Published
2024

15. Differential Expression Analysis of Proteins Regulated by Rare Earth Cerium in Soybean Leaves at Seedling Stage.

Author

Ren Hongyu, Zhang Tianren, Miao Yanli, Li Haoyang, Zhang Shuying, and Zhang Xingwen

Subjects
PROTEIN expression, CERIUM, SOYBEAN
Abstract

This study was to explore the functional mechanism of rare earth regulating soybean leaves and the characteristics and functions of differentially expressed proteins under the regulation of rare earth. In this study, Dongnong 42 was used as material, and 30 mg ⋅ L-1 CeCl3 solution was sprayed on soybean leaves at the seedling stage. Tandem mass tag (TMT) quantitative proteomics technique and bioinformatics analysis were used to identify soybean leaf proteins. A total of 8 510 proteins were identified, and 127 differentially expressed proteins (DEPs) in response to rare earth cerium regulation were identified, among which 64 were upregulated and 63 were down-regulated. The gene ontology (GO) annotation indicated that DEPs were mainly involved in metabolic process, cellular process, response to stimulus, biological regulation, and response to a stimulus; DEPs in cell module categories were mainly involved in cells, cell part, organelle, membrane, membrane part, organelle par, and protein-containing complex; DEPs in molecular functional categories were mainly involved in catalytic activity, binding and antioxidant activity. Kyoto encyclopedia of genes and genomes (KEGG) pathway significantly enriched starch and sucrose metabolism, glycolysis/gluconeogenesis, galactose metabolism, pentose phosphate pathway, and MAPK signaling pathway-plant. These DEPs were mainly involved in photosynthesis, glucose metabolism and stress response. Forty-six differential protein interaction networks were identified by protein interaction network analysis. This experiment provided a reference for studies of the mechanism of rare earth cerium regulating soybean leaf function from the proteomic perspective. [ABSTRACT FROM AUTHOR]

Published
2024

20. The Pharmacokinetics/Pharmacodynamics and Neurotoxicity of Tigecycline Intraventricular Injection for the Treatment of Extensively Drug-Resistant Acinetobacter baumannii Intracranial Infection

Author

Huang,Qi, Zhang,Xingwen, Jia,Aijun, Jiang,Yu, and Xie,Liangyi

Subjects
Pharmacology, Infectious Diseases, Infection and Drug Resistance, Pharmacology (medical)
Abstract

Qi Huang,1 Xingwen Zhang,2 Aijun Jia,2 Qi Huang,3 Yu Jiang,4 Liangyi Xie5 1Department of Pharmacy, Hunan Provincial People’s Hospital (The first-affiliated hospital of Hunan normal university), Changsha, People’s Republic of China; 2Emergency Intensive Care Unit, Hunan Provincial People’s Hospital (The first-affiliated hospital of Hunan normal university), Changsha, People’s Republic of China; 3Department of Pharmacy, Xiangya Hospital, Central South University, Changsha, People’s Republic of China; 4Institute of Emergency Medicine, Hunan Provincial People’s Hospital (The first-affiliated hospital of Hunan normal university), Changsha, People’s Republic of China; 5Department of Laboratory Medicine, Hunan Provincial People’s Hospital (The first-affiliated hospital of Hunan normal university), Changsha, People’s Republic of ChinaCorrespondence: Qi Huang, Hunan Provincial People’s Hospital (The first-affiliated hospital of Hunan normal university), Jiefangxi Road N.61, Changsha, Hunan, People’s Republic of China, Tel +86-731-81866105, Email q12600073@163.comObjective: This study aimed to provide feasible suggestions for intraventricular injection of tigecycline to treat intractable Acinetobacter baumannii intracranial infections by studying its pharmacokinetics/pharmacodynamics and neurotoxicity.Methods: A simple and reliable two-dimensional high-performance liquid chromatography (2D-HPLC) method was used to determine tigecycline concentration. The pharmacokinetics (PK) of tigecycline in cerebrospinal fluid (CSF) was investigated by performing therapeutic drug monitoring (TDM). The pharmacodynamics (PD) of tigecycline was evaluated by its minimum inhibitory concentration (MIC) against XDR A. baumannii. CCK8 assay was used to evaluate the cytotoxicity of different concentrations of tigecycline effect on PC12 cells, and apoptosis assay was analyzed by flow cytometry.Results: Tigecycline retention time in 2D-HPLC was 7.636 min. The lower limit of quantitation (LLOQ) was 0.1mg/L, which met the requirements of concentration determination for TDM. The MIC50 and MIC90 values of tigecycline for A. baumannii were 2 and 4 mg/L, respectively. After a dose of 5mg tigecycline, Cmax in CSF was 37.894 mg/L which was high above the MIC values. The t1/2 of tigecycline was estimated to be 2.73 hours. Tigecycline significantly decreased cell viability as assessed and induced apoptosis of the PC12 cell. The IC50 value of PC12 cells treated with tigecycline was about 51.35 mg/L.Conclusion: Intraventricular injection of tigecycline is a promising method for treating XDR A. baumannii intracranial infection. Since a high concentration of tigecycline in CSF may have potential neurotoxicity, and the t1/2 was short, giving small doses of less than 5 mg at least twice a day may be safer and more effective. Intraventricular injection of tigecycline must be selected cautiously and best carried out under TDM.Keywords: tigecycline, intraventricular injection, XDR A. baumannii, intracranial infection, TDM

Published
2022

27. Biodiversity promotes ecosystem functioning despite environmental change

Author

Hong, Pubin, Schmid, Bernhard, De Laender, Frederik, Eisenhauer, Nico, Zhang, Xingwen, Chen, Haozhen, Craven, Dylan, De Boeck, Hans J, Hautier, Yann, Petchey, Owen L, Reich, Peter B, Steudel, Bastian, Striebel, Maren, Thakur, Madhav P, Wang, Shaopeng, Sub Ecology and Biodiversity, Ecology and Biodiversity, University of Zurich, Mori, Akira, Wang, Shaopeng, Sub Ecology and Biodiversity, and Ecology and Biodiversity

Subjects
stress gradient hypothesis, Environmental change, UFSP13-8 Global Change and Biodiversity, Evolution, Biodiversity, 10127 Institute of Evolutionary Biology and Environmental Studies, Behavior and Systematics, ecosystem function, Ecosystem, 910 Geography & travel, Biology, Ecology, Evolution, Behavior and Systematics, biodiversity, Ecology, Global change, Interspecific competition, environmental change, Nutrients, Droughts, meta-analysis, Chemistry, Geography, 10122 Institute of Geography, 1105 Ecology, Evolution, Behavior and Systematics, Complementarity (molecular biology), Phytoplankton, Ecosystem management, 570 Life sciences, biology, 590 Animals (Zoology), Species richness
Abstract

Three decades of research have demonstrated that biodiversity can promote the functioning of ecosystems. Yet, it is unclear whether the positive effects of biodiversity on ecosystem functioning will persist under various types of global environmental change drivers. We conducted a meta-analysis of 46 factorial experiments manipulating both species richness and the environment to test how global change drivers (i.e. warming, drought, nutrient addition or CO2 enrichment) modulated the effect of biodiversity on multiple ecosystem functions across three taxonomic groups (microbes, phytoplankton and plants). We found that biodiversity increased ecosystem functioning in both ambient and manipulated environments, but often not to the same degree. In particular, biodiversity effects on ecosystem functioning were larger in stressful environments induced by global change drivers, indicating that high-diversity communities were more resistant to environmental change. Using a subset of studies, we also found that the positive effects of biodiversity were mainly driven by interspecific complementarity and that these effects increased over time in both ambient and manipulated environments. Our findings support biodiversity conservation as a key strategy for sustainable ecosystem management in the face of global environmental change.

Published
2022
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31. Biodiversity promotes ecosystem functioning despite environmental change

Author

Hong, Pubin, primary, Schmid, Bernhard, additional, De Laender, Frederik, additional, Eisenhauer, Nico, additional, Zhang, Xingwen, additional, Chen, Haozhen, additional, Craven, Dylan, additional, De Boeck, Hans J., additional, Hautier, Yann, additional, Petchey, Owen L., additional, Reich, Peter B., additional, Steudel, Bastian, additional, Striebel, Maren, additional, Thakur, Madhav P., additional, and Wang, Shaopeng, additional

Published
2021
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34. Design of an X-band TR module based on SICL

Author

Chen He, Zhang Guoan, Sun Chao, and Zhang Xingwen

Subjects
Physics, Dimension (vector space), business.industry, Electromagnetic shielding, X band, Phase (waves), Optoelectronics, Radio frequency, business, Noise figure, Signal, Excitation
Abstract

An X-band four-channel T/R module is designed and fabricated based on SICL(Substrate Integrated Coaxial Line). The module's transmitting channel has high gain and high power and the RF signal is transmitted through SICL to reduce signal leakage. Combined with the method of metal frame, it decreases the crosstalk between the input and output ports of transmitting channel, enhances the signal shielding ability, and reduces the risk of self excitation. Test results show that the dimension of the TR module is $110\text{mm}^{\ast}80\text{mm}^{\ast}10\text{mm}$ , with transmitting power ≥ 35W, receiving gain >35dB, noise figure < 3dB, phase consistency ≤± 15 ° and gain consistency ≤ 1dB.

Published
2021

35. Research on Simulation Technology of RF Microsystem Based on Hardware-in-the-Loop Simulation

Author

Wei Wei, Zhang Xingwen, Xinxing Fei, Wang Yong, and Sun Biao

Subjects
Physical verification, Hardware_GENERAL, Computer science, Frequency band, Microsystem, Miniaturization, Hardware-in-the-loop simulation, Electronic engineering, Electronics, Solid modeling, Radio frequency
Abstract

RF microsystems are the development trend of the miniaturization of electronic devices in the future. As an important means to realize the efficient development of RF microsystems, high precision simulation technology is currently receiving extensive attention. Aiming at the RF microsystem in the Ku frequency band, this paper adopts the hardware-in-the-loop simulation method combining three-dimensional electromagnetic field modeling technology and MMICs cascaded circuit parameter extraction technology to realize the research and verification of the simulation method of the RF microsystem. After physical verification and testing, the simulation results are highly consistent with the test results. In the 6 ∼ 18 GHz frequency band, the simulation accuracy is better than 90%, which can meet the application requirements of high precision simulation of RF microsystems.

Published
2021

42. Supercontinuum Generation by Ghost Pulse

Author

Zhang, Xingwen

Subjects
Negative chirp, Ghost pulse, 500 Natural sciences and mathematics::530 Physics::530 Physics, Supercontinuum generation
Abstract

This dissertation provides a novel method to generate negatively chirped supercontinuum (SC) and details the design, fabrication and complete characterization of the generated SC. According to the SPM theory, an inverse Gaussian pulse should be able to generate negatively chirped SC. In this thesis this kind of inverse Gaussian pulse is termed as “ghost pulse”. However, in practice it is impossible to produce an inverse Gaussian pulse because the pulse intensity can not be negative. Therefore, in order to generate negatively chirped SC, the first difficult challenge is how to obtain the desired ghost pulse. In this work, a 4f-line pulse shaping system and a sum-frequency generation (SFG) setup were built and performed to produce a stable ghost pulse. Due to the Fourier transform limit, narrow spectral bandwidth corresponds to long pulse duration. Thereby, the 4f-line pulse shaping system can produce a long duration pulse E_4f (t) (τ_p≈2 ps) by narrowing the spectral bandwidth of the input pulse. Afterwards, a sum-frequency generation (SFG) nonlinear process was performed between this long pulse E_4f (t) and a fundamental pulse E(t) (τ_p≈200 fs). The center energy of the pulse E_4f (t) was depleted due to the SFG process and thus a ghost pulse E_ghost (t) was obtained. The formation of this ghost pulse was verified by a commercial autocorrelator device and a home-built FROG (frequency-resolved optical gating) setup. Pumping by this ghost pulse and using YAG and sapphire crystals as the working media, we have succeeded in generating negatively chirped SC. For the sake of contrast, a control experiment using the fundamental pulse (τ_p≈200 fs) to generate SC was also carried out. The generated SCs were experimentally characterized with the help of different techniques including autocorrelator, FROG and NOPA (non-collinear optical parametric amplifier). The validation of the experimental results by these different strategies allows us to check the properties of the generated SC systematically. The NOPA and autocorrelator results reveal that the SC generated by ghost pulse is negatively chirped in a round-about way. The FROG results directly prove that the SC is purely generated by ghost pulse and is clear negatively chirped, while the SC generated by fundamental pulse is positively chirped., Diese Dissertation beschreibt eine neuartige Methode zur Erzeugung von negativ gechirptem Superkontinuum (SC) und beschreibt detailliert das Design, die Herstellung und die umfassende Charakterisierung der erzeugten SC. Nach der SPM-Theorie sollte ein inverser Gaußscher Puls in der Lage sein, negativ gechirpte SC zu erzeugen. In dieser Arbeit wird ein solcher inverser Gaußscher Impuls als "Ghost pulse" bezeichnet. Jedoch ist es praktisch unmöglich, einen inversen Gaußschen Puls zu erzeugen, da die Pulsintensität nicht negativ sein kann. Um eine negativ gechirpte SC zu erzeugen, besteht die erste schwierige Herausforderung daher darin, den gewünschten Ghost pulse zu erhalten. In dieser Studie wurden ein 4f-Linien-Impulsformungssystem und ein Summenfrequenzerzeugung-Setup (SFG) aufgebaut und angewendet, um einen stabilen Ghost pulse zu erzeugen. Aufgrund der Begrenzung durch die Fourier-Transformation entspricht eine schmale spektrale Bandbreite einer langen Pulsdauer. Dadurch kann das 4f-Linien-Pulsformungssystem einen Puls E_4f (t) (τ_p≈2 ps) mit langer Dauer erzeugen, indem es die spektrale Bandbreite des Eingangspulses verengt. Anschließend wurde ein nichtlinearer Summenfrequenzerzeugungsprozess (SFG) zwischen diesem langen Impuls E_4f (t) und einem Fundamentalimpuls E(t) (τ_p≈200 fs) durchgeführt. Die Zentralenergie des Pulses E_4f (t) war aufgrund des SFG-Prozesses verringert und so wurde ein Ghost pulse E_ghost (t) erzeugt. Die Formung dieses Ghost pulse wurde durch ein kommerzielles Autokorrelator-Gerät und eine selbst gebaute frequenzaufgelöste optische Nachweismethode (FROG) verifiziert. Mit diesem Ghost pulse konnten in YAG- und Saphirkristallen negativ gechirptes SC erzeugt werden. Aus Kontrastgründen wurde auch ein Kontrollexperiment mit einem Fundamentalpuls (τ_p≈200 fs) zur Erzeugung von SC durchgeführt. Die erzeugten SCs wurden experimentell mit Hilfe einer Vielzahl verschiedener Techniken wie Autokorrelator, FROG und nicht-kollinearer optischer parametrischer Verstärker (NOPA) charakterisiert. Die Validierung der experimentellen Ergebnisse durch diese verschiedenen Strategien erlaubt es uns, die Eigenschaften der erzeugten SC systematisch zu überprüfen. Die Ergebnisse der NOPA und des Autokorrelators zeigen, dass die durch den Ghost pulse erzeugte SC negativ gechirpt wird. Die FROG-Ergebnisse demonstrieren direkt, dass der SC alleine durch den Ghost pulse erzeugt wird und negativ gechirpt ist, während der durch Fundamentalimpulse erzeugte SC positiv gechirpt ist.

Published
2021
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46. Design of Odd Equal Divider Power Synthesis Circuit

Author

Zhang Xingwen, Sun Biao, Kang Xiaoke, and Wang Yong

Subjects
business.industry, Computer science, Amplifier, Electrical engineering, Power (physics), Broadband, Hardware_INTEGRATEDCIRCUITS, Wireless, business, Electrical impedance, TO-18, Hardware_LOGICDESIGN, Interpolation, Electronic circuit
Abstract

As a core part of the power amplifier, the power synthesis unit is concerned to meet the launch requirement of electromagnetic equipment. This paper present two kinds of design methods covering 6 to 18 GHz. One approach is adopt an unequal powder combination with a 1:2 between 2-way powder divider and impedance to realize odd equal power output by high and low impedance circuit matching; an alternate approach is a sector broadband synthesis circuit structure of multi-section to achieve higher power signal transmission through cavity or micro-strip circuit model. It can be seen from the simulation results that for both synthesis circuits, the interpolation loss is less than 0.5 dB and the out-put wave ratio is less than 1.3, which meets the high power synthesis demand of broadband power amplifier.

Published
2020

47. Design of A Miniaturized Ultra-wideband Down Converter Module

Author

Wei Wei, Sun Biao, Zhang Xingwen, Wang Yong, and Xing Jun

Subjects
Digital down converter, business.industry, Computer science, Component (UML), Radar imaging, Process (computing), Electronic engineering, Wireless, Ultra-wideband, Overlay, Modular design, business
Abstract

In order to meet the requirements of electromagnetic countermeasure and radar systems, a miniaturized variable frequency module from 8 to 16GHz is proposed. The module adopts the modular design idea, which is implemented by the vertical overlay assembly of two independent modules, which reduces the plane size. Using multi-layer media substrate combined with bare-chip micro-assembly process, the component size is reduced and circuit integration is improved. In order to realize the requirements of generalization, the module adopts a three-stage mixing scheme, integrates the functions of phase shift, attenuation, pre-selected filtering, and can be powered by a single point from +8 to +20V, making it convenient for use. The measured results show that the compact ultra-wide band down converter meets all the specifications, and can be widely used in various occasions.

Published
2020

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