家用电器的抗浪涌干扰抑制

频谱分析表明,标准测试浪涌波的能量主要分布在低频部分,但其高频部分的能量也是不容忽视的.为了进行可靠的浪涌保护以及满足电磁兼容的要求,压敏电阻与瞬态二极管进行浪涌抑制是十分必要的.     

浪涌保护器件的测试和试验方法（续二）

3.测试和试验方法 3.1 试验浪涌波形为了能良好地保护设备不受浪涌冲击,SPD应通过合理的试验浪涌波检验,需要两种试验浪涌波,一是电缆配对线与地线之间的浪涌波,另一是配对的两导线之间的浪涌波。两种试验浪涌波可通过设备浪涌能量及浪涌电压故障的概率分布和所采用的浪涌数据确定。     

提高多元胞结构半导体放电管浪涌能力的研究

讨论了半导体放电管能量损耗对其浪涌能力的影响.结果表明减小长基区宽度可以明显地降低器件的开通和通态能量损耗,从而有效提高器件的浪涌能力.     

双芯IGCT浪涌电流鲁棒性研究

作为晶闸管类器件,双芯集成门极换流晶闸管(Dual IGCT)必须具备的抗浪涌电流能力研究鲜见报道。基于多单元集成的器件仿真结构模型,揭示了Dual IGCT在浪涌电流下工作时,总电流在GCT-A部分和GCT-B部分间的分配比例会随晶格温度升高而减小。在此基础上,分析了寿命控制技术对Dual IGCT浪涌鲁棒性的影响。结果表明,增大GCT-B的载流子寿命可以提高器件的浪涌鲁棒性,但同时会增大器件的功耗;而在对GCT-B进行载流子寿命控制时,引入具有较大寿命对温度依赖系数的复合中心,可以有效提高Dual IGCT浪涌电流鲁棒性,同时不影响器件的其他性能。最后,提出了一种工艺成本较低的阳极短路Dual IGCT新结构,其在浪涌电流下的晶格温升与传统的Dual IGCT相比大幅减小(约150 K),呈现出极高的抗浪涌能力。     

电缆与连接器(十)

（上接2009年第3期79页） 3．5．11浪涌抑制器件的组合应用 有时候靠一个浪涌抑制器件（SPD）很难满足所有的需求,为了优化SPD的浪涌抑制性能,同时减小生产成本,可以将多个SPD组合使用。图3AT是一个能够承受高功率的气体放电管（GDT）和一个箝位动作迅速的金属氧化物压敏电阻（MOV）的组合应用情况。GDT被触发后可以吸收大部分浪涌能量,当产生过压时,串联电感可以使GDT触发,而MOV可以保护负载不受GDT触发电压的影响。     

机载设备的浪涌抑制

首先分析了机载设备浪涌的特点,对GJB181-1986和GJB181A-2003的浪涌指标进行了详细的分析对比.在此基础上提出了对电压浪涌的抑制方法,分别实现了对机载设备的过压浪涌、欠压浪涌的抑制,并提出了同时实现过压浪涌和欠压浪涌抑制而不中断负载工作的方法.最后对电流浪涌的抑制方法进行了介绍.     

电源的雷电浪涌效应及加固技术研究

雷电浪涌是雷电对电子系统的一种重要的作用形式。雷电对电子系统的影响主要表现在对电源电路的浪涌破坏和干扰上。为研究雷电浪涌对电源的冲击效应,进行了雷电浪涌对直流电源的冲击实验。实验表明,雷电浪涌对直流电源有很大的干扰作用,可使电源产生大的波动或高频噪声。在雷电流涌冲击实验的基础上,对直流电源进行了加固实验,并取得了良好的效果。     

模拟电路浪涌信号产生机理的研究与仿真

针对某型雷达模拟电路中存在的浪涌信号,提出了一种简单、实用的冲激响应理论分析方法。对雷达产生浪涌信号的一个典型电路进行仿真,得出模拟电路产生浪涌的一个重要原因是晶体管的瞬间导通电流过大。提出了一些防止浪涌信号对模拟电路冲击的措施。     

浪涌在发射机配电系统中的危害与预防

文章对尖峰浪涌产生的原因、危害以及抑制浪涌的原理进行了分析,介绍了使用浪涌抑制器时应注意的事项,并通过发射机中抑制浪涌的实际应用,提出了预防浪涌和其他干扰所必须采取的措施。     

应用NTC实现电源浪涌保护技术研究

研究应用NTC实现半导体设备电源浪涌保护技术,对电源浪涌的成因、NTC的特点及电源浪涌保护的原理进行了分析,设计了NTC电源浪涌保护电路,并通过实验展示了NTC抑制浪涌的能力与效果。     

Sensing OFDM systems with timing and frequency offset for cognitive radio networks

In this paper, we consider the detection of orthogonal frequency division multiplexing with timing and frequency offset for cognitive radio over fast time‐varying multipath channels. By making different assumptions on the availability of the timing and frequency offset at the secondary user, we derive two algorithms based on likelihood ratio test and generalized likelihood ratio test, respectively and theoretically obtain the detection performances of them. The proposed algorithms jointly utilize energy of observations and correlation of the cyclic prefix (CP) data. The extensive simulations show that the two algorithms outperform the other CP‐based methods, perform well at very low signal to noise ratio (SNR) and are robust to the CP ratio. Copyright © 2012 John Wiley & Sons, Ltd.     

Secrecy outage analysis in a hybrid cognitive relay network with energy harvesting

In this paper, we investigate the physical layer security of a hybrid cognitive relay network using an energy harvesting relay in presence of an eavesdropper. In the hybrid scheme, a secondary user (SU) as well as a cognitive relay works either in underlay or in overlay mode. In underlay, the transmit power of the SU as well as the relay is limited by the maximum acceptable interference at primary user (PU) receiver as required by an outage constraint of PU, a quality of service for PU. The secondary network consists of a decode and forward relay that harvests energy from radio frequency signal of secondary transmitter as well as PU transmitter to assist the SU in forwarding the information signal to the destination. A time switching relaying protocol is used at the relay. We evaluate the secrecy outage probability of secondary relay network assuming that channel state information of the interfering links from both the SU and relay transmitter to PU receiver is imperfect. Our results reveal the impact of imperfect channel state information, energy harvesting time, tolerable interference threshold, and PU outage constraint on the secrecy outage probability of SU.     

Multi-Rate Access Schemes for MC-CDMA

In order to accommodate different types of traffic in future wirelesscommunications, it is necessary to consider a system, which can operatesatisfactorily at multiple transmission rates. Due to its capability to copewith the hostile frequency selective fading, that limits transmission rate,and its suitability to handle multi-rate data, multi-carrier CDMA (MC-CDMA)has recently drawn considerable attention as a suitable candidate forsupporting multimedia services in wireless communications. Multi-rate accessschemes where users are able to transmit at different data rates on MC-CDMAsystems are presented in this paper. Four multi-rate access schemes: uncodedfixed spreading length (UFSL), coded fixed spreading length (CFSL), multi-codefixed spreading length (MFSL) and variable spreading length (VSL) schemes areproposed. With these schemes, different traffic such as voice, video and highrate data can be transmitted seamlessly through one MC-CDMA infrastructure.A chip-level minimum mean square error combining (MMSEC) technique is employedfor joint energy combining and interference cancellation purpose. Theperformance of these schemes with MMSEC is compared by both theoreticalderivations and simulation results under frequency selective Rayleigh fadingchannels.     

W 波段五腔回旋速调管放大器的设计

W 波段回旋速调管具有高增益和高输出功率的特点,在军用雷达方面有广泛的应用。本方利用电磁粒子模拟 软件CHIPIC 设计了一个W 波段五腔回旋速调管,优化了互作用电路的结构和工作参数,分析了电子注与场的换能 过程以及工作频率对输出效率和增益的影响。该管的工作模式为TE01 模,当工作电压为70kV、电流为6A、频率为 93.8GHz 时获得了167.3kW 的最大输出功率和39.8%的工作效率。当工作频率为93.65GHz 时取得了50dB 的增益和 400MHz 的带宽。该模拟结果对回旋速调管在雷达方面的应用提供了理论依据。     

非正弦波通信时域正交椭圆球面波脉冲设计方法

针对非正弦波信号的频带传输问题,同时为了有效提高非正弦波通信系统的频带利用率及功率利用率,提出了时域正交椭圆球面波脉冲集设计方法。通过参数设置、频段划分、求解方程、Schmidt正交化等步骤设计时域正交椭圆球面波脉冲集,调整脉冲参数实现脉冲集信号的频谱搬移与频谱控制,脉冲集信号为频谱特性可控的带限信号。仿真结果表明:时域正交椭圆球面波脉冲集具有较好的能量聚集性,利用该脉冲集实现多路信息并行传输时,在保证系统具有较好的功率利用率前提下,系统的频带利用率可快速接近奈奎斯特速率。     

Study on Energy Stored in Thin Layers of MEMS Ultrasonic Resonance Separator

The particles suspending in liquid suffer acoustical radiation force from ultrasonic field. The force may cause particles movement and has special advantage to separate particles from liquid in Micro Electro Mechanical Systems （MEMS）. It is important to improve the energy stored in liquid layer so as to increase separation ability for decreasing drive demand in MEMS. Resonance may hugely increase the magnitude and generally be employed in micro separator. The summits of admittance spectrum show the resonance frequencies. It may come from resonance in one layer or multi layers in micro separator. This paper studies the difference of energy stored in layers at each rein frequency. It provides the way to select the most effect separation frequency other than admittance spectrum.     

压电能量收集器件基于有限元仿真比较和研究

利用压电材料制作的器件采集环境中的振动能量,并转化为电能的微尺度器件正日益受到广泛关注。通过有限元仿真分析,研究了新颖的垂直式纳米线阵列结构(VING)和常见的压电悬臂梁结构的能量收集性能。在更贴近实际情况的低频条件下计算了75 000根纳米线阵列结构和压电悬臂梁结构的输出电压以及单位体积能量输出功率,并指出了其各自的特点。最后得出结论:VING更适于在振动强度较大的环境中工作,而悬臂梁结构则更适于在接近其谐振频率的环境中工作。     

频域均衡联合基于能量排序的部分并行干扰删除检测算法

针对频率选择性信道下的DS-CDMA系统,该文提出了一种联合MMSE(最小均方误差)频域均衡与基于能量排序的部分并行干扰删除(MMSE-EOPPIC)的多用户检测算法。该算法首先采用基于重叠剪切法的MMSE频域均衡代替Rake接收机对各用户的数据信息进行初始估计,然后在干扰删除的每个迭代级根据用户能量由强到弱的顺序依次对用户进行部分干扰删除;为了提高每个迭代级检测的可靠性,该文将当前级已经检测出的能量较强用户的硬判决值用于重构当前级能量较弱用户的多址干扰(MAI)。仿真结果表明MMSE-EOPPIC检测算法可以有效提高系统的比特误码率性能。     

Energy Harvesting—Technical Analysis of Evolution,Control Strategies,and Future Aspects

This paper provides a technical analysis of energy harvesting (EH) in the field of power and energy sector, including different aspects of harvesting energy, individual case history, control strategies of harvesting in the field of power and energy sector together with the current trend and future aspects of it. EH is comparatively a new concept which is growing very fast since the 20th century and catching new generation research approaches. This paper not only describes the past and current scenarios of harvesting energy with radio frequency (RF) and renewables but also gives author’s own anticipation of the upcoming future trends of it by comparing the case histories.     

光纤色散对FFH—OCDMA系统误码率的影响

介绍了光纤色散对快跳频光码分多址（FFH-OCDMA）系统结构，分析了系统性能并进行计算机仿真。结果表明，在FFH-OCDMA系统中，光纤色散导致解码自相关光脉冲峰值功率和光脉冲取样能量的降低，进而导致系统误码率（BER）的增加，最后，提出用改变判决门限的方法来降低色散对BER的影响。