The Art of Power Dividing:A Review for State-of-the-Art Planar Power Dividers

In this paper,massive state-of-theart planar power dividers are presented and discussed. The innovations of these superiorly-performanced power dividers lie in the performance breakthrough,physical configurations and function integrations. Eventually,based on the trend presented,the future of the power dividers is predicted. This paper might have inspiration significance to illuminate the way for the development of power dividers.

Compact UWB Power Divider, Analysis and Design

In this paper, two ultra-wide band power dividers are introduced. Compact equal power divider is considered firstly where an extended transmission lines and double open stubs are used in order to increase the bandwidth. Secondly, an unequal UWB power divider is introduced where multi-stage impedance is used. The proposed power dividers are fabricated and measured. The overall sizes of the proposed power dividers are 11.37 × 17.87 mm2 for the equal one and 12.13 × 29.03 mm2 for the unequal power divider. The simulated results are compared with the measured results and good agreement is obtained.

A power divider based on a new kind of composite right/left-handed transmission line (CRLH TL) unit

A new power divider, composed of a novel composite right/left-handed (CRLH) transmission line (TL) unit, is proposed. The properties of the power divider based on four CRLH TL unit cells are investigated theoretically. By adjusting the parameters of the capacitors and the inductors, the power divider shows perfectly symmetric power division at 5.13 GHz, return loss up to ?24 dB, with the transmitted power being close to ?3.1 dB. The phenomena are demonstrated by simulation results. Being compact in size and low-cost, the proposed power divider is very suitable for microwave and millimeter wave integrated circuits.

A new type of Wilkinson dual-frequency power divider with symmetrical transmission line stubs

To realize equal power splitting at two arbitrary gigahertz-frequencies, this paper presents a new type of Wilkinson dual frequency power divider, consisting of three-section transmission lines and a series RLC(resistor, inductor and capacitor)circuit. By equating the [ABCD] matrix of the proposed circuit to that of the quarter-wave impedance transformer, coupled with even/odd mode analyses, the design equations of the proposed network are derived. For verification, two dual-frequency power dividers with dual-band operating frequencies at 0.6 GHz and 3.0 GHz, and 3.8 GHz and 10 GHz respectively are designed and simulated. Simulation results show that the dual-band ratio of the proposed power divider can be as large as 5. Comparisons of the simulation results at X-band and S-band with different power dividers indicate that the proposed dual-band power divider performs better under the scenario of the upper operating frequency extending to X-band.

Property uniformity of thick nickel-based alloy plate for nuclear power steam-generator divider plate

This paper introduces a thick 690 nickel-based alloy plate produced by the former Baosteel Special Steel Co.,Ltd.used as the steam-generator divider plate in the pressurized water reactor nuclear power plant.According to the product characteristics and design requirements of the thick nickel-based alloy plate,multidimensional sampling and testing were conducted to investigate its microstructure and mechanical properties.The results show that all the property indexes of the thick hot-rolled nickel-based alloy plate meet the design requirements,and there is good uniformity in the microstructure and mechanical properties in different dimensions.These findings indicate that China has mastered the core manufacturing technology of thick nickel-based alloy plates for their use as divider plates in nuclear power steam generators.

A Miniaturized Broadband Wilkinson Power Divider Using Micro-Strip Branch Lines

A miniaturized broadband Wilkinson power divider is proposed. Micro-strip branch lines are introduced to replace multiple resistors used in multi-stage Wilkinson power dividers to increase the bandwidth of single-stage Wilkinson power dividers. To demonstrate its performance, an improved single-stage Wilkinson power divider with four micro-strip branch lines was designed. Simulated results show that the insert loss is better than 3.2 dB, the input return loss, output return loss, and isolation are better than 15 dB respectively, across a 76% bandwidth from 18 to 40 GHz. .

Power consumption and flow field characteristics of a coaxial mixer with a double inner impeller

A coaxial mixer meeting the actual demand of a system with high and variable viscosity is investigated. It has an outer wall-scraping frame and a double inner impeller consisting of a four-pitched-blade turbine and Rushton turbine. The power consumption and flow field characteristics of the coaxial mixer in laminar and transitional flow are simulated numerically, and then the distribution of velocity field, shear rate and mass flow rate are analyzed. The simulation results indicate that the outer frame has little effect on the power consumption of the double inner impeller whether in laminar or transitional flow, whereas the inner combined impeller has a great effect on the power consumption of the outer frame. Compared with the single rotation mode, the power consumption of the outer frame will decrease in co-rotation mode and increase in counter-rotation mode. The velocity, shear rate and mass flow rate are relatively high near the inner impeller in all operating modes, and only under double-shaft agitation will the mixing performance near the free surface be improved.In addition, these distributions in the co-rotation and counter-rotation modes show little difference, but the co-rotation mode is recommended for the advantage of low power consumption.

Numerical investigation of granular mixing in an intensive mixer:Effect of process and structural parameters on mixing performance and power consumption

Discrete element method(DEM)simulations of particle mixing process in an intensive mixer were conducted to study the influence of structural and process parameters on the mixing performance and power consumption.The DEM model was verified by comparing the impeller torque obtained from simulation with that from experiment.Impeller and vessel torque,coordination number(CN)and mixing index(Relative standard deviation)were adopted to qualify the particle dynamics and mixing performance with different parameters.A method based on cubic polynomial fitting was proposed to determine the critical mixing time and critical specific input work during the mixing process.It is found that the mixing performance and energy efficiency increases with the decrease of impeller offset.The mixing performance is improved slightly with the increase of blade number and the impeller with 3 blades has the highest energy efficiency due to its low input torque.Results indicate that the energy efficiency and the mixing performance increase with the decrease of filling level when the height of granular bed is higher than that of blade.

Synergistic and interference effects in coaxial mixers: Numerical analysis of the power consumption

This paper is concerned with the design and application of coaxial mixers with the aid of analysis of interaction between each individual impeller. Two types of coaxial mixers pitched blade turbine(PBT)-helical ribbon(HR)and inner-outer HR operated in laminar regime were studied experimentally and numerically. The interaction implies synergistic and interference effects, which was revealed through the investigation of axial circulation rate, energy dissipation rate and power consumption. The influence factors including rotational speed ratio,rotating mode and impeller configuration were explored systematically. Quantitative analysis of power consumption involves three parameters: rate of variation in power consumption, interactive mode and ratio of power consumption. Analysis indicated that some important properties were embodied in the power curve.These properties are one-way and two-way interactions, critical speed ratio and dominant impeller. Finally, a new suggestion for power estimation was given.

A low power quadrature up-conversion mixer for WSN application

This paper presents an up-conversion mixer for 2.4GHz wireless sensor networks in 0. 181xm RF complementary metal-oxide semiconductor （CMOS） technology. It is based on a double-balanced Gilbert cell type. With two Gilbert cells it was applied quadrature modulation. Operational ampli- tiers are used in this design to improve the conversion gain under low power consumption. The mixer design is based on 0.18txm RF CMOS process. And the mixer test results indicate that under 1.8V power supply, with input frequency 2.4 - 2.4835GHz, the conversion voltage gain is 1.2 - 2dB. When the output frequency is 2.4GHz, its power gain is -4.46dB, and its input referred 1 dB com- pression point is -11.5dBm and it consumes 1.77mA current.

Analysis and Design of a Quadrature Down-Conversion Mixer for UHF RFID Readers

A quadrature mixer with a shared transconductor stage is analyzed,including voltage conversion gain, linearity, noise figure, and image rejection. The analysis indicates it has better performance than a conventional Gilbert mixer pair in commutating mode. A quadrature down-conversion mixer based on this topology is designed and optimized for an ultra high frequency RFID reader. Operating in the 915MHz ISM band, the presented quadrature mixer measures a conversion gain of 12.5dB,an IIP3 of 10dBm, an IIP2 of 58dBm, and an SSB noise figure of 17.6riB. The chip was fabricated in a 0. 18μm 1P6M RF CMOS process and consumes only 3mA of current from a 1.8V power supply.

Experimental study on gas–liquid dispersion and mass transfer in shear-thinning system with coaxial mixer

The effects of impeller type, stirring power, gas flow rate, and liquid concentration on the gas–liquid mixing in a shear-thinning system with a coaxial mixer were investigated by experiment, and the overall gas holdup, relative power demand, and volumetric mass transfer coefficient under different conditions were compared. The results show that, the increasing stirring power or gas flow rate is beneficial in promoting the overall gas holdup and volumetric mass transfer coefficient, while the increasing system viscosity weakens the mass transfer in a shearing–thinning system. Among the three turbines, the six curved-blade disc turbine(BDT-6) exhibits the best gas pumping capacity; the six 45° pitched-blade disc turbine(PBDT-6) has the highest volumetric mass transfer coefficient at the same unit volume power.

A numerical study of mixing intensification for highly viscous fluids in multistage rotor-stator mixers

How to achieve uniform mixing of highly viscous fluids with low energy consumption is a major industry demand and one of the hot spots of mixing research.A typical multistage rotor-stator mixer(MRSM)equipped with a distributor was investigated to disclose the effects on the mixing performance and power consumption for highly viscous fluids via numerical simulation,considering the influence factors associated with different geometric parameters of both MRSM and the distributor.The mixing index and power consumption are used to evaluate the performance of the mixers.The dimensionless correlations for the mixing index and the power consumption are established considering the factors including the flow rate,rotor speed,the number of mixing units.Adopting the optimized mixer with the distributor(X1-T1),the mixing index increases to 0.85(obviously higher than 0.46 for the mixer T1 without a distributor),meanwhile the corresponding power consumption is about 1/5 of that of T1 achieving the same mixing effect.It illustrates that the distributor can significantly improve the mixing of highly viscous fluids in the MRSM without the cost of large power consumption.These results would provide a guidance on the design and optimization of multistage rotor-stator mixers in industrial applications.

Kenics型静态混合器中幂律流体与颗粒混合过程分析

针对Kenics型静态混合器内固体颗粒在幂律流体中的孤岛现象的产生机理进行研究。运用Fluent数值模拟固相颗粒与CMC水溶液在Kenics静态混合器中的混合过程,并利用浓度变异系数(COV)对颗粒分布特性进行量化分析。研究表明:提高流体表观黏度和流体入口速度,颗粒停留时间缩短,COV值降低,混合效果提高。在第4~8个扭旋叶片中间截面上均形成了两对对称的无粒子孤岛,降低流体表观黏度和提高流体入口速度,孤岛边界更清晰。扭旋叶片诱导的内流涡旋和近壁面涡旋有较高的涡量,涡旋中心局域形成无粒子孤岛,相邻叶片交错区域,随着涡旋耗散孤岛消失。

弥合教育数字鸿沟——美国《国家教育技术规划(NETP 2024)》报告要点与思考

2024年1月,美国教育部发布第七版《国家教育技术规划(NETP 2024)》,从教育数字资源访问、数字教育教学设计和教育数字化使用领域等角度,提出了数字访问、设计和使用三种教育数字鸿沟,呼吁采取行动,为支持学习技术的获取、设计和使用的不平等建立系统解决方案。了解该规划有助于厘清教育数字化转型中存在的数字鸿沟,为学习者和教育者提供公平获取教育技术的机会。文章采用内容分析法和比较分析法,阐述美国发布该规划的背景和目的,比较了七版规划的差异,分析和勾勒规划的侧重点,并从技术整合视角论述了教育数字化转型中存在的数字鸿沟及其缓解策略,最后从教育强国建设视角反思了该规划对我国教育技术发展规划的启示,以期为加速教育数字化转型,加快建设教育强国提供参考。

超高功率电弧炉变压器和电抗器技术参数设计

电弧炉变压器主要作用是降低供电电压,产生大电流,在保证供电效率的情况下,适应电弧炉冶炼所需的电弧弧长,保证电弧炉冶炼过程的安全性。同时提供不同挡位的电压和电流,以满足冶炼过程需要。电抗器主要作用是增加线路的无功功率,降低短路电流和功率因数,稳定电弧燃烧。同时提供不同挡位的电抗,以满足冶炼过程不同工况的需要。变压器和电抗器技术参数的合理设计是保证电弧炉稳定冶炼的关键,依据电弧炉所需的冶炼效率及出钢量,系统分析电弧炉变压器和电抗器参数的设计原理。从分析可知,变压器的容量是基于电弧炉的通电时间及出钢量进行确定,而变压器的二次电压、额定电流及电抗器容量等参数是基于电弧冶炼稳定性的约束条件进行计算。计算结果与JB/T 9640-2014参考值进行对比分析,结果匹配度较好。

声共振混合器高黏度流体混合的功耗特性研究

声共振混合利用机械共振产生高加速度振动,从而促进流体流动,其功耗特性对于其设计及应用具有重要作用。为研究声共振混合器的功耗特性,基于CFD建立了声共振混合过程仿真模型,分析了高黏度流体声共振混合过程壁面对物料的作用力和做功功率,探究了黏度和振动参数改变对混合器功耗特性的影响,并建立了声共振混合器混合功率的预测函数。研究结果表明,在混合过程中,壁面对液相做功的瞬时功率呈现先减少后稳定波动的趋势,而有效功率呈现先增加后稳定波动的趋势,这种不同的变化趋势是由于两者的相位差发生变化所导致的。增加振幅、频率或等加速度下低频大振幅都能够增加瞬时功率和有效功率,并减少液相进入稳定流动阶段所需吸收的外界能量。

基于阶梯阻抗谐振器的双频宽带滤波功分器

为了更好地满足无线通信系统对多功能、多频段射频前端器件的要求,提出了一种基于阶梯阻抗谐振器的双频宽带滤波功率分配器。首先,使用单个T形谐振器实现双频滤波单元,同时采用阶梯阻抗技术引入了单独可调的高次模用于展宽双频功分器的高频通带带宽;其次,利用枝节加载技术实现额外谐振模式的引入,展宽了双频滤波功分器低频通带带宽;为了实现小型化设计,对部分微带线进行弯折,使得整个电路结构更加紧凑。此外,利用T形谐振器自身的滤波特性和在微带馈线上加载的开路枝节,在带外产生四个可控的传输零点,提高了通带外选择性;通过在微带馈线上加载扇形枝节和在输出端口引入隔离电阻,有效改善了滤波功分器的带内阻抗匹配效果和隔离度。为了进一步验证,对所提出的滤波功分器进行了加工和测试。该滤波功分器的中心频率为2.83 GHz和4.87 GHz,相对带宽分别为10.6%和11.7%,通带隔离度均大于14.5 dB。测试和仿真结果基本一致。

基于环形多模谐振器的双频滤波功分器设计

本文设计了一种基于环形多模谐振器的零点可控双频滤波功分器。通过微扰加载,实现双频滤波器功能;利用枝节加载,提高了带宽和带外选择性;采用融合设计方法,将该滤波器与功分器进行集成,完成双频滤波功分器设计;通过在输出端口间引入电阻,提高端口间隔离度。为了验证设计的正确性,设计、加工和测试了该功分器,实测结果和仿真结果基本吻合,当功分器S_(11)<-10 dB时,工作频段分别为2.14~2.52 GHz和4.54~4.84 GHz,端口间隔离度最大达到45 dB。