基于UWB的消防员室内协同定位算法

为了在复杂火场环境下获取消防员的精确位置,提出基于超宽带(ultra-wideband,UWB)的消防员室内协同定位算法,充分利用目标到UWB基站以及到其他目标的测距信息进行定位.采用线性拟合方式对测量距离中存在的标准偏差进行预处理;针对目标位置解算及非视距(non-line-of-sight,NLOS)误差缓解问题,...     

基于特征模理论分析的超宽带小型化准八木天线设计

文中设计了一款超宽带准八木天线。根据特征模理论对传统的准八木天线进行分析,并结合天线理论,在不改变天线原有尺寸的情况下,通过采用弯折、切槽等技术,增大了电流路径,拓宽了低频的工作带宽。天线尺寸为0.256 λ₀×0.256 λ₀×0.002 λ₀(λ₀为最小工作频率所对应的波长),工作带宽为0.78 GHz～1.58 GHz。与初始天线相比,相对带宽从32.0%提高至67.8%。通过前后比可以看出,天线具有良好的定向性能,可以满足人脑探测活动的需求。     

超宽带脉冲信号波形失真仿真与分析

超宽带无线信道的频率依赖特性直接影响到超宽带接收机的设计和以脉冲波形为基础的多址技术。本文针对频率依赖特性对超宽带脉冲信号波形产生的影响,分别从相位谱和幅度谱两个方面分析超宽带脉冲信号的相位失真和幅频失真特性,建立了描述脉冲波形失真特性的数学模型。使用该模型对高斯二阶导数脉冲信号的波形失真进行仿真分析,得到了只发生相位响应失真、只发生幅度响应失真、以及同时发生相位—幅度响应失真的脉冲波形。     

改进蝴蝶算法的神经网络天线建模

为提高天线建模效率,改变传统建模方法速度慢、效率低的问题,提出了一种用改进的蝴蝶算法(BOA)优化多层前馈神经网络(back propagation neural network, BPNN)的天线建模方法。首先,以多层前馈神经网络为基础网络,建立蝴蝶算法优化的BP神经网络,解决BP神经网络预测精度低的问题。其次,在蝴蝶算法中融入天牛须算法(BAS),用天牛须算法替代蝴蝶算法的局部寻优过程,减小蝴蝶算法的空间复杂度、解决蝴蝶算法易陷入局部最小值的问题,创建改进的BOA-BP神经网络对天线进行精准建模。设计实例表明,该网络的预测精度达到了99.60%,相比于传统的BPNN和未改进蝴蝶算法优化的BPNN,预测S₁₁的误差分别减少了47%和40.9%。此外,改进的BOA算法的运行时间相对于粒子群算法和遗传算法也分别减小了80.86%和82.79%,大大降低了网络运行的时间成本。综上,改进的BOA优化后的BPNN的建模精度和速度均得到了提高,验证了改进的蝴蝶算法作为一种新型神经网络优化策略的可行性和有效性。     

Defected Ground Structure Multiple Input-Output Antenna For Wireless Applications

In this paper, the investigation of a novel compact 2 × 2, 2 × 1, and 1 × 1 Ultra-Wide Band (UWB) based Multiple-Input Multiple-Output (MIMO) antenna with Defected Ground Structure (DGS) is employed. The proposed Electromagnetic Radiation Structures (ERS) is composed of multiple radiating elements. These MIMO antennas are designed and analyzed with and without DGS. The feeding is introduced by a microstrip-fed line to significantly moderate the radiating structure’s overall size, which is 60 × 40 × 1 mm. The high directivity and divergence characteristics are attained by introducing the microstrip-fed lines perpendicular to each other. And the projected MIMO antenna structures are compared with others by using parameters like Return Loss (RL), Voltage Standing Wave Ratio (VSWR), Radiation Pattern (RP), radiation efficiency, and directivity. The same MIMO set-up is redesigned with DGS, and the resultant parameters are compared. Finally, the Multiple Input and Multiple Output Radiating Structures with and without DGS are compared for result considerations like RL, VSWR, RP, radiation efficiency, and directivity. This projected antenna displays an omnidirectional RP with moderate gain, which is highly recommended for human healthcare applications. By introducing the defected ground structure in bottom layer the lower cut-off frequencies of 2.3, 4.5 and 6.0 GHz are achieved with few biological effects on radio propagation in human body communications. The proposed design covers numerous well-known wireless standards, along with dual-function DGS slots, and it can be easily integrated into Wireless Body Area Networks (WBAN) in medical applications. This WBAN links the autonomous nodes that may be situated either in the clothes, on-body or beneath the skin of a person. This system typically advances the complete human body and the inter-connected nodes through a wireless communication channel.     

Blockchain and IIoT Enabled Solution for Social Distancing and Isolation Management to Prevent Pandemics

Pandemics have always been a nightmare for humanity, especially in developing countries. Forced lockdowns are considered one of the effective ways to deal with spreading such pandemics. Still, developing countries cannot afford such solutions because these may severely damage the country’s economy. Therefore, this study presents the proactive technological mechanisms for business organizations to run their standard business processes during pandemic-like situations smoothly. The novelty of this study is to provide a state-of-the-art solution to prevent pandemics using industrial internet of things (IIoT) and blockchain-enabled technologies. Compared to existing studies, the immutable and tamper-proof contact tracing and quarantine management solution is proposed. The use of advanced technologies and information security is a critical area for practitioners in the internet of things (IoT) and corresponding solutions. Therefore, this study also emphasizes information security, end-to-end solution, and experimental results. Firstly, a wearable wristband is proposed, incorporating 4G-enabled ultra-wideband (UWB) technology for smart contact tracing mechanisms in industries to comply with standard operating procedures outlined by the world health organization (WHO). Secondly, distributed ledger technology (DLT) omits the centralized dependency for transmitting contact tracing data. Thirdly, a privacy-preserving tracing mechanism is discussed using a public/private key cryptography-based authentication mechanism. Lastly, based on geofencing techniques, blockchain-enabled machine-to-machine (M2M) technology is proposed for quarantine management. The step-by-step methodology and test results are proposed to ensure contact tracing and quarantine management. Unlike existing research studies, the security aspect is also considered in the realm of blockchain. The practical implementation of the proposed solution also obtains the results. The results indicate the successful implementation of blockchain-enabled contact tracing and isolation management using IoT and geo-fencing techniques, which could help battle pandemic situations. Researchers can also consider the 5G-enabled narrowband internet of things (NB-IoT) technologies to implement contact tracing solutions.     

Design of compact fractal patch antenna for X/Ku/K-band applications

This paper presents a fractal-based compact new monopole antenna for wideband applications. The miniaturization has been achieved by incorporating Minkowski and Koch-snowflake fractals. The proposed antenna design is etched on top of Rogers RT/5880 dielectric material with a dimension of $8.10\times 8.10$ mm². The antenna is designed, analyzed, fabricated, and tested in the laboratory. The proposed geometry operates over a 8.62–22.40 GHz with fractional bandwidth (FBW) of 88.84% and VSWR is less than 2. The proposed monopole antenna exhibits nearly omnidirectional radiation patterns over the entire resonating band with a gain of 1–2.91 dBi and a radiation efficiency of more than 60.5%. Also, the measured results of the prototype make an excellent agreement with the simulated counterpart. Further, the antenna gives good time-domain characteristics. Therefore, the proposed miniaturized antenna can be used in X/Ku/K-band applications.     

基于厚薄膜混合基板的超宽带垂直互联设计

针对三维集成电路中基板层间信号垂直互联问题，基于厚薄膜基板的优良特性，设计了一种超宽带的同轴到带状线再到微带线的过渡结构，能够工作到80 GHz。这种垂直结构采用LTCC为基板，旋涂BCB膜层，适用于系统级封装。该结构利用“水滴”匹配的方法，并嵌入空气腔抑制寄生电容，有效地改善了互联结构的射频传输性能。仿真结果表明，其背靠背（同轴-带状线-微带线-带状线-同轴）结构在0～80 GHz频段范围内，回波损耗均低于-17 dB，插入损耗均优于-0.5 dB，驻波比均低于1.35，具有良好的超宽带传输特性。     

Parachute shape ultra-wideband wearable antenna for remote health care monitoring

Wireless body area networks (WBAN) is used to measure patients' health conditions continuously. Different kinds of sensors are required to measure health conditions. When such types of antennas are used on the human body, they are flexible with the movements. The usage of wearable devices is currently increasing in the biomedical field. The presented wearable antenna is suitable for biomedical applications. The presented ultra-wideband (UWB) flexible parachute shape wearable antenna is fabricated on a jeans textile substrate. The prototype antenna has a −10 dB measured impedance bandwidth of 5800 MHz (7 to 12.8 GHz) with average radiation efficiency of 75.28%. The prototype antenna's size is 40 × 40 mm² (1.32 × 1.32 ${\lambda }_0^2$ at centre frequency 9.9 GHz) and a peak gain of 4.5 dB at 12.33 GHz. The fabricated antenna is suitable for biomedical applications in X-band frequencies and can be implemented with a low-cost manufacturing process. The radiating element is made by conductive copper tape. Muscle-equivalent phantoms are used to analyze the body effect on antenna performance. The radiation effect emitted by the presented antenna on the human body is calculated by the specific absorption rate (SAR) value. The maximum SAR value of the proposed antenna is 1.84 W/kg at 12.33 GHz. This leads to promising results for wearable applications related to remote health care monitoring, such as biotelemetry and mobile health with a sensor-driven approach.     

超宽带MIMO印刷单极子天线的设计

为了适应UWB系统对天线小型化的需求,设计了一款紧凑型UWB-MIMO天线,天线尺寸仅为23 mm×31 mm×1.6 mm。通过引入阶梯状结构,极大改善了天线带宽。测试结果显示所设计的UWB-MIMO天线的阻抗带宽为2.9～28 GHz,带宽比为9.6∶1。整个频段内互耦程度小于-15 d B,中高频段小于-20 d B,很好地满足了UWB系统对MIMO天线带宽和互耦程度的要求。在此基础上,对地板进行改造,实现了天线的双陷波特性。