Design and development of high linearity millimeter wave traveling-wave tube for satellite communications

The linearity of the traveling-wave tube is a very important characteristic for a modern communication system. To improve the linearity of the traveling-wave tube at no expense of the saturated output power and overall efficiency, a modified pitch profile combined with a small adjustment of operating parameters is proposed. The optimal design of the helix circuit is evaluated theoretically by a large signal analysis, and the experimental test is also carried out to make a comparison of performance between the novel and original designed traveling-wave tubes. The experiments show that the saturated output powers and efficiencies of these two tubes are close to each other, while the linearity of the traveling-wave tube is obviously improved. The total phase shift and AM/PM conversion at saturation of the novel tube, averaged over the operating band, are only 30.6°/d B and 2.5°/d B, respectively, which are 20.1°/d B and 1.6°/d B lower than those of the original tube, respectively. Moreover, the third-order intermodulation of the novel tube is up to 2.2 d Bc lower than that of the original tube.

A novel slotted helix slow-wave structure for high power Ka-band traveling-wave tubes

A novel slotted helix slow-wave structure （SWS） is proposed to develop a high power, wide-bandwidth, and high reliability millimeter-wave traveling-wave tube （TWT）. This novel structure, which has higher heat capacity than a conven- tional helix SWS, evolves from conventional helix SWS with three parallel rows of rectangular slots made in the outside of the helix tape. In this paper, the electromagnetic characteristics and the beam-wave interaction of this novel structure operating in the Ka-band are investigated. From our calculations, when the designed beam voltage and beam current are set to be 18.45 kV and 0.2 A, respectively, this novel circuit can produce over 700-W average output power in a frequency range from 27.5 GHz to 32.5 GHz, and the corresponding conversion efficiency values vary from 19% to 21.3%, and the maximum output power is 787 W at 30 GHz.

A staggered double vane circuit for a W-band traveling-wave tube amplifier

Based on the combination of a staggered double vane slow wave structure （SWS） and round electron beam, a 200-W W-band traveling-wave tube （TWT） amplifier is studied in this paper. The main advantages of round beam operation over the sheet beam is that the round beam can be formed more easily and the focus requirement can be dramatically reduced. It operates in the fundamental mode at the first spatial harmonic. The geometric parameters are optimized and a transition structure for the slow wave circuit is designed which can well match the signal that enters into and goes out from the tube. Then a TWT model is established and the particle-in-cell （PIC） simulation results show that the tube can provide over 200-W output power in a frequency range of 88 GHz-103 GHz with a maximum power of 289 W at 95 GHz, on the assumption that the input power is 0.1 W and the beam power is 5.155 kW. The corresponding conversion efficiency and gain at 95 GHz are expected to be 5.6% and 34.6 dB, respectively. Such amplifiers can potentially be used in high power microwave-power-modules （MPM） and for other portable applications.

Analysis of impact pressure,rock-breaking effect,and ground vibration induced by the disposable CO_(2)fracturing tube

The technology of expansion fracturing with liquid CO_(2)(EFLCO_(2))has attracted increasing attention due to reduced vibration and damage.The disposable fracturing tube has been developed and is gradually replacing the Cardox tube.However,there is a lack of impact pressure testing of disposable tubes under real working conditions,selection of gas explosion design parameters,and systematic analysis of blasting vibration.This limitation has constrained the widespread application of disposable fracturing tubes in engineering.A joint monitoring of the pressure-time curves in the disposable tubes and boreholes was conducted.The rock-breaking effect of varying hole spacing parameters in the EFLCO_(2)design was analyzed,and a systematic study was carried out on the vibration peak value,frequency,and energy characteristics.The results show that(1)the pressure distribution characteristics,stress peak value,and duration in the disposable tubes are different from those of Cardox tubes,which show multi-peak distribution,low-pressure peak value,and short duration.The correlation between the pressure in the disposable tube,filling pressure,and liquid CO_(2)weight is established,and a theoretical calculation method for the borehole wall pressure is proposed;(2)The hole spacing in rocks of different hardness is suggested;and(3)At the same scale distance,the peak particle velocity(PPV)caused by EFLCO_(2)(PPVCO_(2))is significantly smaller than that caused by blasting(PPVexplosive).The ratio of PPVexplosive to PPVCO_(2)is a power function related to scale distance,and a distance-related zonality exist in this relationship.The frequency composition of the vibration signal caused by EFLCO_(2)is relatively simple with a narrow frequency band.Its PPV and energy are mainly concentrated in the low-frequency band.This research contributes to the optimization of disposable fracturing tubes,gas explosion design,and vibration hazard control.

An Open Rectangular Waveguide Grating for Millimeter-Wave Traveling-Wave Tubes

Millimeter-wave traveling-wave tube （TWT） prevails nowadays as the amplifier for radar, communication and electronic countermeasures. The rectangular waveguide grating is a promising all-metal interaction circuit for the millimeter-wave TWT with advantages of high power capacity, fine heat dissipation, scalability to smaller dimen- sions for shorter wavelengths, compact structure and robust performance. Compared with the traditional closed structure, the open rectangular waveguide grating （ORWG） has wider bandwidth, lower cut-off frequency, and higher machining precision for higher working frequencies due to the open transverse. It is a potential structure that can work in the millimeter wave and even Terahertz band. The rf characteristics including dispersion and interaction impedance are investigated by both theoretic calculation and software simulation. The influences of the structure parameters are also discussed and compared, and the theoretical results agree well with the simula- tion results. Based on the study, the ORWG will favor the design of a broadband and high-power millimeter-wave TWT.

Design of a Novel Folded Waveguide for 60-GHz Traveling-Wave Tubes

The 60-GHz traveling-wave tube （TWT） prevails nowadays as the amplifier for the satellite communication and electronic countermeasures. The folded waveguide （FW） is a promising all-metal slow-wave structure （SWS） for the 60-GHz TWT with advantages of robust performance, fine heat dissipation, considerable power and bandwidth. A novel FW periodically loaded with rectangular grooves is analyzed for the purpose of gaining higher power and gain. The rf characteristics are investigated by numerical simulation, and the nonlinear large- signal performance of such a TWT is analyzed by a 3I） particle-in-cell code MAGIC. Compared with normal circuits, relatively higher continuous-wave power （40-56 W） and similar bandwidth （5 GHz） are predicted by simulation. Meanwhile, the designed operation voltage is 10.5 kV, which keeps the low-voltage advantage of the popular helix TWT competitor. The novel FW will favor the design of a broadband and high-power 60-GHz TWT

Design of a re-entrant double-staggered ladder circuit for V-band coupled-cavity traveling-wave tubes

The re-entrant double-staggered ladder slow-wave structure is employed in a high-power V-band coupled-cavity traveling-wave tube. This structure has a wide bandwidth, a moderate interaction impedance, and excellent thermal dissipation properties, as well as easy fabrication. A well-matched waveguide coupler is proposed for the structure. Combining the design of attenuators, a full-scale three-dimensional circuit model for the V-band coupled-cavity traveling- wave tube is constructed. The electromagnetic characteristics and the beam wave interaction of this structure are investigated. The beam current is set to be 100 mA, and the cathode voltage is tuned from 16.8 kV to 15.8 kV. The calculation results show that this tube can produce a saturated average output power over 100 W with an instantaneous bandwidth greater than 1.25 GHz in the frequency ranging from 58 GHz to 62 GHz. The corresponding gain and electronic efficiency can reach over 32 dB and 6.5%, respectively.

An open-styled dielectric-lined azimuthally periodic circular waveguide for a millimeter wave traveling-wave tube

An open-styled dielectric-lined azimuthMly periodic circular waveguide （ODLAP-CW） for a millimeter-wave traveling-wave tube （TWT） is proposed, which is a modified form of a dielectric-lined azimuthally periodic circular waveguide （DLAP-CW）. The slow-wave characteristics of the open-styled DLAP-CW are studied by using the spatial harmonics method, which includes normalized phase velocity and interaction impedance. The complicated dispersion equations are numerically solved with MATLAB and the results are in good agreement with the simulation results obtained from HFSS. The influence of structural parameters on the RF properties is investigated based on our theory. The numerical results show that the optimal thickness of the metal rod can increase the interaction impedance, with the dielectric constant held fixed. Finally, the slow-wave characteristics and transmission properties of an open-styled structure are compared with those of the DLAP-CW. The results validate that the mode competition is eliminated in the improved structure with only a slight influence on the dispersion characteristics, which may significantly improve the stability of an open-styled DLAP-CW-based TWT, and the interaction efficiency is also improved.

基于六点刚度试验的输送带翘曲问题分析

圆管带式输送机具有封闭运输的优点,但相较于普通带式输送机也存在一些缺点,如输送带横向刚度引起的输送带翘曲问题。文中针对输送带翘曲问题,基于六点刚度试验进行输送带仿真模型的建立,并通过仿真模型对输送带翘曲现象进行了定性分析。结果表明,输送带的翘曲量与输送带的横向刚度呈非线性增加的关系,与张力呈非线性减小的关系,并且随托辊间距的增加而增加,本研究为输送带的选型和圆管带式输送机的设计提供一定的参考。

6 W@80 K空间同轴脉管制冷机设计与实验研究

针对某空间红外载荷需求,基于Sage平台搭建了同轴脉管制冷机整机模型,根据仿真结果对冷头结构参数进行了设计计算。在此基础上,利用实验方法探究了回热器填充方式、惯性管组合方式、充气压力、输入功率、冷头方向对制冷机性能的影响,并与仿真结果比较,两者吻合度较高。研制成功的脉管制冷机整机质量为3.5 kg,输入功率150 W时,无负荷制冷温度为39.74 K,可获得7.23 W@80 K的冷量,整机相对卡诺效率13.26%,在空间用同轴脉管制冷机中处于先进水平。

基于EDEM仿真玉米高位投种结构参数分析与试验

为解决育种小区玉米高位投种过程中播种质量和粒距均匀性普遍较差等问题,针对排种器与导种管相对位置对粒距均匀性的影响进行了研究分析。通过对投种过程的理论分析,得出高速作业不同粒距条件会影响种子脱离种盘时产生的水平方向分速度,使得种子在导种管内产生碰撞,导致其排出的轨迹无法预测,播种粒距均匀性也随之下降。利用EDEM离散元分析软件对投种过程进行仿真试验,结果表明:在垂直距离344mm的条件下,150~230mm粒距采用水平距离82mm,230~300mm粒距采用水平距离84mm,能够在满足农艺要求并获得较好的粒距均匀性。进行了台架试验验证,结果表明对比未优化单体,优化后的单体能够获得较好的播种质量,粒距均匀性变异系数最大为12.04%,符合小区玉米精密播种的作业要求。

某拱形空间管桁架结构稳定性能分析

大跨空间结构常因整体稳定不足而造成严重的安全隐患,针对某实际工程中拱形空间管桁架结构采用参数化分析方法进行整体稳定性能分析研究,考虑了缺陷幅值、重要杆件以及几何参数等因素对结构稳定承载力的影响。研究表明:在不利组合工况作用下,临界荷载系数为6.03,结构稳定性较好;结构对初始缺陷不敏感,其稳定系数变化不足4%;斜腹杆局部失稳下结构仍具有较强的承载能力;考虑双重非线性效应,在一定范围内增大其宽高比和外径比可以显著提高结构稳定承载能力,并给出宽高比控制在0.5~1之间、外径比控制在0.5左右的设计建议。研究结果为此类结构的设计与施工提供了参考。

翅片管式换热器翅片结构对空气侧性能的影响

建立5mm管径翅片管式换热器百叶窗翅片的物理模型和数学模型,模拟分析百叶窗翅片开窗角度和换热器管间距对空气侧性能的影响,结果表明:在相同迎面风速下,空气侧的换热量及表面传热系数均随百叶窗开窗角度的增大而增大,风机功率随之大幅增加;空气侧的换热量及表面传热系数均随管间距的减小而增大;综合考虑换热量、风机功率及空气侧表面传热系数,开窗角度20°、管间距17.1 mm时换热器空气侧性能更优。

龙门山生物多样性博览园电气设计策略探讨

结合成都世园会邛崃分会场——龙门山生物多样性博览园项目实例,归纳博览建筑电气设计基本原则;分析供配电系统设计的关键点和难点问题;阐述光导筒节能照明;探讨展厅高大空间消防电气设计、温室展厅植被保障供电问题。

熔岩管探测的定位方法

针对月球熔岩管内定位,选取海南省海口石山火山熔洞作为模拟月球熔岩管实验区域,利用立体视觉、激光雷达和IMU传感器进行模拟月球熔岩管环境下的定位实验,应用立体视觉定位、激光扫描点云定位、视觉融合IMU定位、激光点云融合IMU以及视觉激光融合IMU定位等方法进行定位处理,对各类方法在不同光照与地形条件熔岩管环境下定位结果的平均误差与稳健性进行对比分析。实验结果表明,立体视觉在长距离行走模式下平均误差可达3.59%,但平均误差与稳健性受制于光照条件;激光雷达平均误差同视觉水平接近,局部区域平均误差为1.89%,但稳健性受数据采集率与视场角影响;立体视觉、激光雷达与IMU集成的定位在光照与地形起伏十分恶劣的熔岩管区域内取得了稳健定位结果,是进行长距离连续定位的优先选择。研究结论为后续月球熔岩探测定位传感器配置与定位方法研究提供了有益参考。

空间管桁架结构体育馆建筑施工全过程模拟研究

文中以某体育馆钢结构工程为例,对空间管桁架结构体育馆建筑施工方案进行分析。应用有限元软件对吊装阶段和卸载阶段进行模拟分析,通过对吊装阶段成果的卸荷模拟,找到施工期间处于往复荷载作用下的支架并进行加强处理;采用分级分步的卸载策略,能够显著减少构建承受的应力集中和节点变形,有效预防结构设计过程中可能产生的过度动态响应,确保整体结构的稳定性和安全性。

无人机集群曲线虚拟管道空间满足规划

虚拟管道宽度直接影响了管道内无人机的流速,但目前虚拟管道规划的方法并不能保证管道宽度,容易造成堵塞,严重影响无人机通行效率。对此,提出一种虚拟管道空间满足规划方法,可以在包含障碍物的环境中得到一条满足虚拟管道空间要求的管道生成线。主要包括路径搜索和轨迹优化,基于快速探索随机树*(rapidly exploring random tree*,RRT*)搜索,通过空间检测判断每段路径周围是否有足够空间,若无足够空间则重新拓展搜索,替换掉空间不足的路径段。在轨迹优化过程中,使用均匀B样条参数化轨迹,并设计碰撞代价函数和光滑代价函数,使轨迹远离障碍物,为虚拟管道规划提供足够空间。仿真测试验证了所提方法在大规模集群中的优越性和鲁棒性。在仿真测试中,15架无人机集群通行时间平均降低20%。

长管呼吸器应用于深水导管架施工安全管理

在国家和海洋石油行业“深水战略”背景下,海洋石油行业得到了蓬勃发展,深水海洋石油平台项目不断增多。导管架平台作为应用最广泛的固定式平台,相比于浅水导管架,建造阶段难度更大、风险较高。文章聚焦于建造阶段安全管理,重点分析管腿内受限空间施工作业风险,以及常规通风方式的特点和存在的不足之处。并重点阐述了长管呼吸器替代常规通风模式的工作原理、实际应用效果、应急管理拓展应用及可推广性,以期更好地控制安全风险,保证作业人员安全。

基于RFID的停车位车辆检测装置设计

在城市化发展过程中,汽车数量呈现快速增长趋势,城市停车难成为一个十分突出的问题。因此,设计开发一种智能高效的停车位车辆检测装置显得尤为必要。该装置主要包括独立按键、12864液晶显示、RFID射频模块、红外对管等组件。系统通过红外对管检测车辆是否进入或离开停车位,并通过RFID射频模块识别车辆的身份,判断是否有权限进行停车。当车辆进入或离开停车位时,系统会自动检测和更新停车位状态,并在12864液晶显示屏上显示相关信息。当有未经授权的车辆试图停放时,系统会控制相关设备进行警示和防护。本设计方案具有体积小、成本低、功能强大、操作简单、安装方便等优点,适用于停车场、小区等停车管理场所。

Physical design and cooling test of C-band standing wave accelerating tube

The physical design and cooling test of a C-band 2MeV standing wave （SW） accelerating tube are described in this paper. The designed accelerating structure consists of 3-cell buncher and 4-cell accelerating section with a total length of about 163mm, excited with 1MW magnetron. Dynamic simulation presents that about 150mA beam pulse current and 30% capture efficiency can be achieved. By means of nonlinear Gauss fit on electron transverse distribution, the diameter of beam spot FWHM （full width at half maximum of density distribution） is about 0.55mm. Cooling test results of the accelerating tube show that frequencies of cavities are tuned to 5527MHz and the field distribution of bunching section is about 3：9：10.