Dual Band Switched Beam Textile Antenna for 5G Wireless Communications

This paper presents the single element dual band switched beam textile antenna.The antenna can operate at frequencies of 0.7 and 2.6 GHz using for 5G wireless communication applications.Textile fabric is considered to be used for substrate layer at the parts of a microstrip antenna for wireless body area network.The beam pattern of antenna can be switched into two directions by changing the position of shorted-circuit points at each edge of antenna.The main beam direction is 45°/225°when corner A is shorted while it steers at 135°/315°when corner B is shorted circuit.The advantage of the proposed antenna is the decrease of the problems like interference,light weight,flexibility and ability to switch beam easily.In addition,the results of the fabricated antenna are compared with the simulated ones.Moreover,the antenna is bent with curvature radius of 6 mm in forward direction.The effects of the bent antenna are studied.The results can confirm that radiation patterns of the bending antenna can be pointed into two directions when changing the positions of shorted circuit.Therefore,the proposed antenna can switch beam patterns,it is flexible,and it can operate at dual-band frequency on textile.

Beam-Switching Antenna Based on Plane Dipole Structure

A novel method for designing a beam-switching antenna with the plane dipole is presented. The antenna is composed of double dipoles placed at the center of an active square structure that is divided in four equal sectors by metallic sheets. Metallic patches at the outside of the structure are used to enhance the radiation performance of the antenna. In each step, the diodes in one sector are on, whereas other diodes are off. The sector with off-state diodes defines the direction of the radiation pattern. An antenna model is designed on the substrate of FR4. The proposed antenna operates from 4.8 GHz to 5.5 GHz with gain of 6.3 dBi and F/B （front to back ratio） of 13.2 dBi when the operating frequency is 5.2 GHz. The antenna radiation pattern can be swept in the entire azimuth plane in four steps with a 3 dB beamwidth of 90%. The results reveal that the antenna could be used in the base station of the wireless communication systems.

A 2.4 GHz Switched Beam Antenna for Indoor Applications Using Angle of Arrival Estimation

This study introduces a new design of planar antenna array for ISM band applications at 2.4 GHz. This prototype is switched beam antenna, namely planar antenna with four meandered slotted triangular elements (PAFMSTE), which is proposed for wireless indoor applications. The Base Station (BS) equipped with this planar antenna is preferred to be at the center position on the room ceiling to cover all sectors of the room. It is designed to use four directional triangular elements arranged to form a square planar antenna array. The PAFMSTE is used to obtain optimal directivity in four directions in azimuth plane with 3 dB beamwidth of 90°at a specific orientation of 30°in elevation plane. Switched parasitic technique is used to enable PAFMSTE to steer a directional beam through four locations by using four PIN diodes switches. The High Frequency Structure Simulator (HFSS) is used as an efficient simulation tool to optimize the performance of the PAFMSTE antenna. The fabrication and measurements of the PAFMSTE antenna are introduced. The proposed antenna enable radio positioning via Angle of Arrival (AOA) information collected from nearby devices. Then, the Cramér-Rao Bound (CRB) is presented for AOA estimation using identically and equally spaced antenna elements. The CRB depends on the directivity, where the maximum values of CRB are 1.35 × 10-3 and 8 × 10-3 at HPBW of 60° and 90°, respectively.

基于LSTM的多站点协作波束切换算法

毫米波频段拥有非常丰富的频谱资源,支持更高速的数据传输,因此成为通信领域近年来的研究热点。基于大规模输入输出(Massive Multiple Input Multiple Output,mMIMO)的波束成形技术可以有效补偿毫米波的高路损,是5G毫米波通信中的一项关键技术。但是在高速移动场景下,信道变化加速,必须进行频繁的波束切换才能保证良好的通信质量,故而大大增加了信令开销与资源消耗。如何在高动态场景下降低波束切换开销、提升波束切换速度与效率成为关键问题。针对直射径(Light of Sight,LOS)被遮挡情况下的复杂信道环境,文中提出了一种基于长短期记忆(Long Short Term Memory,LSTM)网络的多站点协作波束切换算法,根据过去一段时间的波束信息,学习信道环境与服务波束序号的内在联系,并预测当前时刻切换的最佳波束。仿真结果表明,与基于当前信道环境信息的遍历搜索算法相比,所提波束切换算法在上行发射功率较高时性能接近,在上行发送功率较低时,性能更优,体现了所提算法的优势。

细长竹木圆棒双激光对射自动检测系统设计

针对细长竹木圆棒胚体存在的表面凹坑、开裂等外观缺陷,设计了一种双激光对射式自动检测系统。机械结构采用载物链条使细长竹木圆棒整体平移并在弹性压板下滚动,由对称布置的双激光斜入射至压板和圆棒贴合部位,实现对竹木圆棒表面的双螺旋扫描和空隙检测;控制部分以西门子S7-200 Smart PLC为主体,设计了与实体链条同步的数字链条进行并行控制。测试结果表明,系统相对于人工检测漏检率为0,具有成本低、效率高、可靠性高、易于使用等特点,可有效解决细长竹木圆棒胚体表面质量初筛问题。

一种宽带双极化波束切换微带天线的设计

以海港码头集装箱堆场的远程(无人化)操控系统为应用背景,提出一种控制方法简单和可实现性好的宽带双极化波束切换微带天线系统。该系统整体由微带阵列天线和波束控制电路两部分组成,其中微带阵列天线包含天线阵A和天线阵B两种类型。所涉及的双极化微带天线采用新型双贴片结构,使得天线实现较宽工作带宽的同时保持较高的极化隔离度;同时,通过在底层辐射贴片上开正方形环槽,实现天线的小型化。波束控制电路采用SP6T射频开关芯片,通过合理的电路设计布局,将两组射频开关集成于一块电路板,在保证低损耗、高速的多波束切换的同时减小了电路尺寸。实测结果表明:该天线的带宽达到21.8%(反射系数小于-10 dB),隔离度大于20 dB,在整个工作频段内该天线系统六个波束能够无缝覆盖-90°~90°工作区,增益优于12 dBi,双极化性能良好。

低地球轨道卫星星座地球固定足印模式覆盖域切换方法

在低地球轨道卫星星座中,当采用地球固定足印模式时,波束在覆盖域之间的切换会影响对地覆盖的仰角,进而影响通信质量。针对地球固定足印模式下的覆盖域切换问题,提出了一种覆盖域切换方法。首先,设计了覆盖域划分机制,使覆盖域拓扑保持规则性;然后,以最大限度地增大波束对地面的最小仰角为目标,设计了切换时刻选择机制和目标覆盖域选择机制。所提方法考虑了极轨星座和倾斜轨星座的差异,同时支持2种星座。以OneWeb和Telesat星座为仿真场景,验证了所提方法。仿真结果表明,所提方法能够有效增大波束对地面覆盖的最小仰角,从而有助于提升链路质量。

智能高速铁路中基于低轨卫星网络的通信关键技术研究

智能高速铁路是构建现代综合交通运输体系的重要组成部分,建立支持高移动性、高速率、高可靠性、高实时性的通信链路是列车安全运行的基石。针对高速铁路空间跨度范围大、轨旁通信设备成本高、越区切换频繁等问题,探讨基于低轨卫星互联网技术实现车地通信的可能性及关键技术。分析智能高速铁路通信业务需求并根据不同的业务类型采用对应的专网或公网进行承载。研究了基于公网卫星互联网络的高速铁路无线接入架构。并在此基础上进一步探讨了面向智能高速铁路的卫星接入与低时延传输、星地链路多普勒频偏、星内/间波束切换等关键技术,以期实现低时延、高可靠的星地通信链路。

跨座式单轨换梁型道岔制造工艺

[目的]由于跨座式单轨换梁型道岔部件种类多、内部结构复杂、变形风险大,在制造过程中容易出现零部件安装位置度超差、焊接热变形及应力集中等问题,导致产品达不到设计质量的要求。因此,有必要对跨座式单轨换梁型道岔的制造工艺进行系统性的研究。[方法]介绍了跨座式单轨换梁型道岔概况;分析了跨座式单轨换梁型道岔结构特征和材料属性,从制造工艺重难点、工艺路线规划、工艺设计及工装设计等多个方面进行了针对性的研究;提出一套适用于跨座式单轨换梁型道岔的制造工艺,并对所提制造工艺的实施效果进行了验证。[结果及结论]所采用的工装胎架与焊接工艺能够将道岔各部件的尺寸精度控制在设计要求范围内,配合振动时效处理能够有效改善结构应力的分布状态、降低结构焊后残余变形风险,确保道岔装配后的线型尺寸达标。

下穿铁路咽喉道岔区线路加固体系研究

研究目的:由于道岔区轨道刚度和质量分布不均匀及其固有的不平顺性,结构受力比正线复杂。道岔一直是病害高发区域和养护维修的难点,因此顶桥下穿铁路咽喉道岔区比铁路正线风险高、难度大。基于此,本文提出一种新的受力性能好、适用范围广、应用于顶桥下穿多股道铁路咽喉道岔区的加固体系。研究结论:(1)横梁按照简支梁结构计算与实际横梁受力状态不相符,对纵横梁加固体系进行数值模拟分析时,将纵梁、钢轨、扣轨梁及岔枕等构件考虑在内,与实际工程中横梁的受力状态较为相符;(2)路基模量的变化对横梁和钢轨位移影响较小,为防止施工中顶桥区域及其两侧路基塌陷,建议采取适当注浆措施;(3)本文研究对顶桥下穿多股道既有铁路道岔区工程加固体系设计具有借鉴意义。

Bending of Timoshenko beam with effect of crack gap based on equivalent spring model

Considering the effect of crack gap, the bending deformation of the Timoshenko beam with switching cracks is studied. To represent a crack with gap as a nonlinear unidirectional rotational spring, the equivalent flexural rigidity of the cracked beam is derived with the generalized Dirac delta function. A closed-form general solution is obtained for bending of a Timoshenko beam with an arbitrary number of switching cracks. Three examples of bending of the Timoshenko beam are presented. The influence of the beam＇s slenderness ratio, the crack＇s depth, and the external load on the crack state and bending performances of the cracked beam is analyzed. It is revealed that a cusp exists on the deflection curve, and a jump on the rotation angle curve occurs at a crack location. The relation between the beam＇s deflection and load is bilinear, each part corresponding to an open or closed state of crack, respectively. When the crack is open, flexibility of the cracked beam decreases with the increase of the beam＇s slenderness ratio and the decrease of the crack depth. The results are useful in identifying non-destructive cracks on a beam.

Practical realization of dual S arm antenna for beam steering applications

A dual S shaped micro strip antenna with a realistic feed is proposed for generation of tilted beam radiation pattern pertaining for beam steering applications. To achieve this, four feeding points are located at a distance of 5.6 mm from the antenna centre. These feeding points when excited one by one generate four tilted beams in four different space quadrants, thus yielding a beam steerable antenna. Importantly, since the proposed antenna is symmetrical in the structure, all the four tilted beams have the same radiation pattern characteristics. A further enhancement of the antenna bandwidth is also achieved using 100-μm capacitive coupling between the feed and the antenna strip.

Impact of Phase Noise on TDMS Based Calibration for Spaceborne Multi-Beam Antennas

For spaceborne multi-beam antennas(MBAs), time division multiplexed switching(TDMS) based calibration receiver can reduce implementation costs effectively and is very suitable for large-scale applications. However, in practice, random phase noise imposed by noisy local oscillators can cause significant performance degradation in TDMS-based calibration systems. Characterization of phase noise effects is therefore crucial for practical applications. In this paper, we analyze the impact of phase noise on the calibration performance for a MBA system. Specifically, we derive the relationship between the probability of correct amplitude/phase estimation and various practical factors involving the signal-to-noise ratio(SNR), the standard deviation of phase noise, the given tolerance region, and the length of the spreading code. The results provide high efficiency for evaluating the calibration performance of the MBAs based on TDMS, especially for precisely anticipating the impact of phase noise. Finally, the accuracy of the derived results is assessed by simulations in different scenarios.

上跨电气化铁路系杆拱桥吊杆更换技术

顺河高架系杆拱桥为长90 m的下承式拱桥,是连接济南市南北交通的干线,并跨越胶济铁路济南东站西侧交通要道。检测发现该桥吊杆存在不同程度的损伤,需全部更换。新吊杆采用GJ15-19型环氧钢绞线整束挤压式吊杆,内部钢绞线采用5层隔离防腐,以提高耐久性。桥梁跨越高铁等电气化线路,下部作业空间受限,施工窗口期短,采用配置转换梁的抱箍式临时兜吊系统和梁底移动式挂篮更换吊杆。抱箍式临时兜吊系统张拉端设置在拱肋与桥面之间,避免了施工对公路交通的影响,且抱箍可拆卸重复利用;转换梁和梁底移动式挂篮克服了梁下作业空间小的难题,实现了铁路运营零干扰的目标。吊杆更换时首先安装临时吊杆实现第一次荷载转移后拆除原吊杆,然后安装新吊杆实现第二次荷载转移,全桥吊杆更换完成后进行全桥调索,最后进行新吊杆防腐和临时吊杆拆除。吊杆更换后桥梁受力状态良好,桥面线形满足设计要求。

100 kHz高功率高光束质量纳秒激光振荡器

高功率、高重复频率纳秒脉冲激光广泛应用于激光切割、激光焊接等领域。随着激光重复频率的提升,特别是高于50 kHz时,单个周期有限的时间内难以积累足够的上能级粒子,调Q脉冲的稳定性成为了激光器设计的难点。当前主要采用主振荡器的功率放大器(MOPA)方案,直接振荡获得兼具高功率、高重复频率及高光束质量的纳秒脉冲激光还比较困难。通过对激光动力学过程的仿真模拟,定量分析了高重复频率调Q过程中脉冲强度稳定性与泵浦速率的关系,并利用负透镜使振荡器工作在具有较大基模体积的热近非稳区,实现了Nd:YAG声光调Q激光振荡器在高重复频率、高功率、高光束质量三方面的均衡设计。首次利用侧泵模块实现了100 kHz高功率高光束质量纳秒脉冲激光的直接振荡产生,脉冲强度的离散系数仅为0.041,激光输出功率超过142 W,脉冲宽度为165 ns,光束质量因子M^(2)为1.5。

基于位置信息辅助的网格化波束切换方法

随着通信技术的发展,越来越高的通信频段得以采纳。然而电磁波衍射能力随频率的增加而降低,新一代通信系统变得更加依赖视距传播。在复杂移动场景下频繁切换波束,增加了过多的系统开销和延迟。针对该问题,提出一种基于位置信息辅助的网格化波束切换方法,利用可视路径中存在时最佳波束对保持不变的特点,划分网格波束一一对应关系及覆盖分布结构,建立位置⁃波束映射表,基于用户位置信息和运动状态计算下一时刻切换点。仿真和分析结果表明,所提方法相比非网格切换方式系统频谱效率显著提高,且所提正六边形网格切换性能优于方格,波束切换概率降低了50%,保障了通信质量,验证了基于位置信息辅助的网格化波束切换方法的合理性。

基于扇区化光波束切换的站址受限可见光通信覆盖方法

传统的静态朗伯和非朗伯光波束配置难以较好地解决发射器站址受限问题。针对单一发射器的应用场景,提出了一种基于扇区化光波束切换的信道站址受限可见光通信覆盖方法。该方法采用商业可用的倾斜非朗伯光波束,根据接收器在不同位置反馈的状态信息,动态地确定能提供最佳覆盖信噪比的候选光波束,构建定向传输链路。仿真结果表明:在典型室内环境下,与传统静态朗伯光波束配置相比,该方法通过增加2个或3个候选扇区波束切换选项,接收器可分别获得4.48 dB、5.94 dB的平均信噪比增益。

K波段可调功率分配比的MEMS五端口环形结研究

提出了一种基于MEMS悬臂梁开关的五端口环形结的结构,以实现可调谐的功率分配比。在结构上,采用MEMS悬臂梁开关控制环形结信号线是否接地短路,进而控制整体电路的拓扑结构,达到输出端口的功率分配比可调的效果。建立了五端口环形结等效电路的S参数微波系统模型,并通过理论模型与仿真结果相比较,验证了模型的正确性。利用该模型可知,对于四分之一波长时,在UP态,端口1的微波信号功率被等分至端口2和端口4,端口3和端口5近乎无输出;在DOWN态,端口1的微波信号功率被分至端口2、端口3、端口4和端口5输出,其中端口2和端口4的输出功率相等,而端口3和端口5的输出功率为端口2或端口4的一半。经过有限元软件验证,在K波段中心频率22 GHz附近,UP态时S_(11),S_(31),S_(51)均小于-20 dB,S_(21),S_(41)均大于-3.3 dB;DOWN态时S_(11)小于-17 dB,S_(21)-S_(31)和S_(41)-S_(51)均接近3 dB,验证了设计的有效性。

基于天通卫星系统的天基测控技术

针对卫星测控资源紧缺的现状,为满足未来大规模卫星用户对测控资源的使用便利性这一需求,研究利用天通卫星进行近地低轨卫星测控服务的能力。天通作为高轨移动通信卫星系统,具有传输实时方便、服务安全可靠和综合效费比高等多方面的特点。首先,分析了天通卫星对不同倾角、轨道高度卫星的测控覆盖时长,以及对载人航天任务空间站和火箭进行测控的服务能力。然后,基于天通民用系统现有的系统架构,详细介绍了天通系统支持低轨测控的系统改造方案以及工作流程。最后,结合目前的技术发展趋势和天通卫星能力现状,描述了天通卫星在天基测控和低速中继两种任务场景中的应用前景。

面向低空预警雷达的信号处理控制平台设计与实现

为应对以民用无人机为代表的低小慢目标“黑飞”“滥飞”所带来的低空安全威胁以及巡航导弹、战术导弹所带来的低空军事威胁,文中引入数字波束合成技术,设计并实现了一种面向低空预警雷达的信号处理控制平台,该平台具有实时性强、运算量大、传输速率高等特点。通过选用高速光纤传输与串行总线VPX技术,同时采用高性能模数转换器、超大规模现场可编程门阵列及高速专用数字信号处理芯片,实现了此平台的硬件架构设计,并在此平台上实现了一种基于数据流驱动的软件信号处理方案。得益于灵活的系统架构和丰富的硬件资源,该信号处理控制平台可以适应新技术的快速应用,便于低空预警雷达功能的升级扩展及性能的进一步提升,有效应对低空威胁。