Cross-Modulation Interference and Mitigation Technique for Ultrawideband PPM Signaling

The detection issues of ultrawideband (UWB) signals depend on the type of modulation scheme that is used during the transmission. Cross-modulation interference (CMI) is a problem that is specific to UWB pulse-position-modulation (PPM) signaling. In this paper, the effects of CMI on the performance of noncoherent UWB receivers are analyzed. The probabilities of error for transmitted-reference (TR) and energy detector (ED) receivers in the presence and absence of CMI are derived. Optimal and suboptimal CMI avoidance algorithms, which are based on novel acquisition techniques, are proposed for Rake receivers. The results show that the performance degradation in both receivers, which is due to the CMI effects, can be significant, depending on the modulation index. TR receivers still can be functional in the presence of CMI, and the target performance level determines the modulation index to be used. It is unlikely that effects of CMI on the performance of ED receivers in the presence of CMI are more severe relative to TR receivers, and the performance level is not acceptable. As a result, PPM signaling is not an appropriate modulation technique for ED receivers that are operating in the CMI region, unless CMI mitigation algorithms can be developed. Furthermore, the proposed optimal and suboptimal algorithms are two promising schemes for avoiding the CMI effects and, consequently, for improving the performance of Rake receivers operating in the CMI region.     

一种2.45 GHz微波二极管整流电路

为了提高用于微波无线功率传输的微波整流效率,本文采用微带结构实现了一个2.45 GHz的微波二极管整流电路.仿真实验结果证明在输入功率约为20 dBm的情况下,获得了大于50%的整流效率.通过完善和改进电路,可以进一步提高整流的效率,并应用于微波整流天线.     

熔拉与腐蚀光纤探针传输特性的研究

用实验方法测量了用熔拉或腐蚀的方法制备的光纤探针的传输效率随光纤圆锥角的变化关系,作出传输效率曲线,通过测定光纤探针传输效率的实验,我们看到:在小锥角的情况下,用熔拉法制备的光纤探针与腐蚀的方法制备的光纤探针的传输效率基本相同。在大锥角的情况下,用腐蚀法制备的光纤探针传输效率高于熔拉的方法制备的光纤探针的传输效率。在锥角为50.4°时,腐蚀的光纤探针传输效率为78.8%,熔拉的光纤探针传输效率为76.6%。在相同的条件下,两者的传输效率的差别随入射光波长的增加而下降。     

基于改进蚁群算法的高能效WSN协作传输策略*

针对传统传感器网络分簇不均匀,数据传输能耗相对较高的问题,提出了I-CoopACO(Cooperative transmission scheme based improved Ant Colony Optimal algorithm)算法.该算法在协作LEACH (Low Energy Adaptive Clustering Hierar-chy)的技术基础上,改进了成簇过程,使得分簇规模更加均匀;在稳定传输阶段,利用节点剩余能量和传输功耗构建启发因子,通过改进的蚁群算法搜索下一跳中继节点获得最优节点,使得传输功耗更低,能耗更均衡.仿真结果表明,在随机分布的感知网络中,I-CoopACO算法减少了传输能耗,均衡了网络负载,延长了网络工作寿命,比协作LEACH算法延长了64.93％的工作寿命.     

400 Mbit/s CMI transmission experiment using a 1.3 ?m LED

A 400 Mbit/s CMI optical transmission experiment has been successfully conducted, using an LED, a GI multimode fibre and a 250 MHz bandwidth monolithic equalising amplifier. In this experiment, 5 km transmission distance has been achieved. The transmission characteristics and required transmission bandwidth are reported.     

A novel method for progressive image transmission using blocked wavelets

The techniques of progressive image transmission (PIT) divide image delivery into several phases. PIT's main objective is to efficiently and effectively provide an approximate reconstruction of the original image in each phase. Therefore, this study proposes the blocked wavelet progressive image transmission (BWPIT) method based on the wavelet transformation and the spatial similarity of pixels, to reduce the bit-rate and increase the image quality in an early phase of PIT. Experimental results show that the transmission bit-rate and the image quality of BWPIT are significantly better than those of bit-plane method (BPM), improved bit-plane method (IBPM), and wavelet-based progressive image transmission (WbPIT) method in each early phase.     

基于电流镜积分的红外探测器读出电路设计

详细分析了电流镜积分(CMI)读出电路的工作原理、设计过程和CMI结构的噪声,并用CSMC 0.5μm CMOS工艺对所设计的电路进行仿真和版图设计,仿真结果表明CMI结构在电源电压为5 V,积分电容为2 pF时能提供一个较大的电荷存储能力(6.25x107个电子);在光生电流为50 pA时,探测器偏压稳定在3.615...     

The Effects of Digital Random Errors on the DMI Code Power Spectrum

The power spectrum of the DMI coded signal containing random errors is investigated. Results of experiments on DMI code transmission are given, confirming that low-frequency components increase according to line errors. These experimental results agree with the theoretical values for a wide error rate range. The investigation method presented in this paper can be applied to the error estimation of other line codes, such as CMI code.     

Energy efficient MAC protocol for delay‐sensitive data transmission over wireless sensor network

This paper presents an energy efficient medium access control (MAC) protocol for delay‐sensitive data transmission over wireless sensor network. In general, energy consumption and delay depend on channel monitoring interval (CMI) and data sensing period at each sensor node. Based on this fact, we propose a new preamble structure to effectively advertise CMI and avoid the overhearing problem. In order to pursue an effective tradeoff between energy consumption and delay, we also develop a CMI determining algorithm that searches for a sub‐optimal solution with a low computational complexity in a distributive way. Finally, experimental results are provided to compare the proposed MAC protocol with existing sensor MAC protocols. Copyright © 2010 John Wiley & Sons, Ltd.     

相控阵测控系统时频及标校信号一体化光传输设计

为了实现对相控阵测控系统不同通道间信号幅度、相位的精确加权,就必须保证时频信号和标校信号的准确传输.针对传统相控阵测控系统时频及标校信号传输网络设计存在的相位一致性差、安装复杂、价格高昂、后期维护性较差等问题,设计了一种新型时频及标校信号一体化光传输网络.实验测试数据分析和工程实例表明,该新型一体化光传输网络在性能、成本、可扩展性以及安装维护等方面均比传统设计有明显提升.随着相控阵测控系统的通道数越来越多,新型一体化光传输网络的工程优异性会更加突出.     

适用于多载波共频谱传输的干扰消除方式

针对多载波共频谱传输应急卫星通信系统,各干扰载波互不相关,且干扰载波的功率远大于扩频信号的功率,干扰载波对扩频信号存在严重的干扰,因此对于扩频信号的恢复,载波重构与干扰消除处理是必须的。对于多载波干扰消除其实现方式可分为串行干扰消除和并行干扰消除2种,为此分析和比较了2种典型实现方式,提出了基于数字重采样的改进方案。分析结果表明,基于数字重采样的串行干扰方式更适合多载波共频谱传输应急系统卫星通信系统的应用。     

随钻测量电磁信道分析的等效传输线法

等效传输线法用于随钻测量电磁传输信道的分析，在当前仍然是一种比较有成效的方法。本文对现有近似法中所采用的等效传输线模型作了一些改进，使之在物理图象上更为确切，并能够对井下激励装置有关参数的影响进行估计。     

Error-correcting code for optical-fibre transmission systems

A simple error-correcting code for optical-fibre transmission systems is proposed, and its correcting principle is explained. This code offers the same advantages as the CMI code, which is widely used in optical-fibre transmission systems. Moreover it has the ability to correct a single error in a block. Owing to this ability, the maximum repeater space can be increased.     

耦合传输线信道传输矩阵建模及串扰抵消效果分析

针对高速互连系统中传输线上的串扰问题,基于电磁耦合理论,研究了耦合传输线信道传输矩阵的性质,建立了以下两种情况的耦合传输线信道传输矩阵模型及其矩阵分解形式,分别是：（1）考虑受扰线两边各一条相邻微带线对受扰线的串扰;（2）考虑受扰线两边各两条相邻微带线对受扰线的串扰.给出了上述两种情况下基于耦合传输线信道传输矩阵分解形式的串扰抵消方案,并利用仿真工具ADS对其进行了验证.结果表明：信号抖动和失真大幅下降,串扰抵消效果良好,并且第二种情况下的串扰抵消效果优于第一种情况.该结果说明了在基于耦合传输线信道传输矩阵进行串扰抵消时,考虑两边各两条相邻微带线的串扰效果较好,对保持高速信号完整性具有一定的实际应用价值.     

飞控数据的远距离传输及抗干扰设计

从硬件设计、电路实现方面介绍了一种用于对飞控数据进行远距离传输的实现过程,并且就传榆过程中的干扰因素进行了分析,提出了一些相应的解决措施,经过对传统的远距离传输方法进行了分析以后系统采用了一种新型的并行传输的方法来实现飞控数据和地面测试台之间数据的传输,所设计的新型通信方式可以提高传输的速度,增强了抗干扰能力,可在复杂工业环境下正常运行。     

Mitigation of cross-modulation interference in UWB energy detector receivers

For ultra-wideband (UWB) pulse position modulation (PPM) signalling, cross-modulation interference (CMI) occurs when the amount of the pulse-position shift is less than the maximum excess delay of the multipath channel. Such CMI severely degrades the bit error rate (BER) performance of energy detector (ED) receivers. To alleviate the adverse effect of CMI, in this letter we propose an enhanced energy detector (EED) combined with block-orthogonal-coded PPM (BOC-PPM). Each PPM frame is chopped into several sub-windows and the outputs of sub-windows are combined to form the decision statistic. The optimum combining scheme is derived based on the maximum likelihood (ML) criteria. Through analysis and simulations, we show that E-ED can significantly suppress CMI and thus performs well in the CMI region.     

一种S波段LTCC带通滤波器的改进设计

设计了一种小型化的低温共烧陶瓷(LTCC)滤波器,该滤波器电路由电容耦合的二阶谐振腔组成。设计了该滤波器的三维多层结构,利用组件间的耦合效应,产生一个传输零点,提高了滤波器性能。仿真结果表明,该滤波器中心频率为3.41GHz,相对带宽为5.9%(200MHz),体积为3.8mm×2.8mm×0.8mm,在S波段的通讯,雷达等射频系统有广泛的应用。     

石英/氰酸酯玻璃钢复合材料的宽频特性研究

采用四端口网络理论分析了极化方式、介电常数与损耗角正切对天线罩透波率的影响,讨论了石英/氰酸酯玻璃钢复合材料的传输特性。数值仿真和实测结果表明,在频带1.2～18 GHz,水平方位角-40°～40°范围内,厚度为1.8 mm的石英/氰酸酯平板功率传输系数均大于60%,表现出良好的宽频特性。     

基于FPGA的数字式血氧饱和度测量仪设计

针对人体血氧饱和度连续无创测量的要求,设计了一套基于FPGA的数字式血氧饱和度测量仪。该仪器采用双波长光源透射吸收式测量、光电管宽带接收、基于FPGA的数字信号处理等技术,以及在上位机采用校准对比、工作函数计算等数据处理方法,得到了血氧饱和度计算公式,实际测量误差在1%以内。试验表明：该仪器通过数字化设计解决了模拟电路易受干扰、体积较大等缺点,提高了仪器稳定性,测量误差满足设计要求。     

一种915MHz紧凑型肖特基二极管微波整流电路

为了提高射频标签(RFID)中基于肖特基二极管微波整流电路的效率,采用微带结构实现了一种915 MHz紧凑型的整流电路。该微波整流电路具有质量轻、尺寸小、整流输入功率动态范围大等特点,设计的仿真和实验结果显示:输入微波功率在13 dBm~22 dBm的情况下,均获得了高于60%的整流效率。通过完善改进电路,可以进一步提高整流的效率,并应用于微波无线能量传输或大型RFID的微波整流天线。