基于DSP的飞机电缆故障定位设备设计

针对飞机电缆故障定位的特点,介绍了一种基于DSP的飞机电缆故障定位设备的设计。利用低压脉冲反射法为被测电缆注入窄带脉冲,采用等效采样对脉冲回波信号进行采集,通过DSP软件对采集数据进行处理,计算电缆故障位置,并将结果通过CAN总线传送到上位机,达到对电缆故障定位的目的。     

A novel Parzen probabilistic neural network based noncoherent detection algorithm for distributed ultra-wideband sensors

Ultra-wideband (UWB) has been widely recommended for significant commercial and military applications. However, the well-derived coherent structures for UWB signal detection are either computationally complex or hardware impractical in the presence of the intensive multipath propagations. In this article, based on the nonparametric Parzen window estimator and the probabilistic neural networks, we suggest a low-complexity and noncoherent UWB detector in the context of distributed wireless sensor networks (WSNs). A novel characteristic spectrum is firstly developed through a sequence of blind signal transforms. Then, from a pattern recognition perspective, four features are extracted from it to fully exploit the inherent property of UWB multipath signals. The established feature space is further mapped into a two-dimensional plane by feature combination in order to simplify algorithm complexity. Consequently, UWB signal detection is formulated to recognize the received patterns in this formed 2-D feature plane. With the excellent capability of fast convergence and parallel implementation, the Parzen Probabilistic Neural Network (PPNN) is introduced to estimate a posteriori probability of the developed patterns. Based on the underlying Bayesian rule of PPNN, the asymptotical optimal decision bound is finally determined in the feature plane. Numerical simulations also validate the advantages of our proposed algorithm.     

调制和编码对超宽带接收机性能改善的比较

1 INTRODUCTION Ultra- wideband (UWB) technology can achieve 100Mbps high- speed wireless communications by use of GHz bandwidth short pulses. Because it has some merits such as very low radio power, difficult to be detected, good penetration and centimeter level location ability, it can be used in secret communications, target detection, personnel search and so on military applications. Since the large bandwidth of UWB signal cause the channel to be extreme frequency selectivity, a con…     

基于希尔伯特-黄和小波包的UWB信号检测方法

针对希尔伯特-黄变换在超宽带脉冲检测中检测性能受限于信噪比的问题,研究并分析了筛选终止条件以及小波包去噪方法,结合新终止条件,给出了希尔伯特-黄变换与小波包分析联合检测的新方法。采用新方法对噪声中的超宽带信号进行检测分析,并运用均方根误差公式对该方法的检测性能进行仿真比较。仿真图表明,新方法能较为准确地重构出淹没在强噪声下的脉冲,成功克服HHT变换在检测超宽带脉冲时受噪声强度影响较大的问题,从而改善强噪声环境下脉冲信号的检测效果。     

基于电阻型频率选择表面的超宽带紧耦合阵列

针对接地板严重影响紧耦合天线阵列(Tightly Coupled Array,TCA)阻抗带宽的问题,设计了一种基于电阻型频率选择表面(Resistive Frequency Selective Surface,RFSS)的多层结构超宽带TCA,分析了电阻膜方阻及单元间耦合对阻抗带宽的影响,并对其扫描及未扫描时的性能进行了仿真分析.结果表明:通过在天线阵列与接地板之间加载开口谐振环结构的RFSS,可减小接地板反射,抑制天线短路点,显著增加其阻抗带宽,其辐射性能在整个带宽内均较稳定;由于RFSS加入了损耗,天线阵列增益有所降低.该多层结构TCA具有带宽宽、体积小、易共形等特点,在超宽带小型化相控阵天线中有良好应用前景.     

基于UWB穿墙定位中NLOS误差的优化方法

针对室内定位中受非视距因素影响下的无线信号穿墙导致定位发生偏移的现象,因无线电信号传播中具有波动性强、易干扰的特点,采用抗干扰性强、穿透力高以及测距值优的超宽带技术采集测量数据。本文将信号穿墙推导公式与无线信号对数衰减模型融合处理采集到的距离值数据,通过衰减模型减少了穿墙时信号损失的能量,提高测距值的准确性,通过最小二乘法减少测距时的累计误差,提高定位精度。通过实际实验场景测试得出：本方法在穿墙环境下定位精度可达到0.28m,满足精度要求,可以为一般的位置需求提供服务。     

一种新型超宽带磁天线

该文设计制作了一种新型实用的超宽带磁天线。天线采用平衡馈电,文中对天线的回波损耗、辐射性能和时域响应进行了数值仿真和实验测试。在驻波比小于2时天线有107%的阻抗带宽,大约100%的方向图带宽,工作频段完全覆盖超宽带通信频谱。研究表明,天线有大于5dB的平稳增益,能够不失真地传播脉冲波形。而且由于磁场能量占优,不易于与近场物体互耦,特别适合于室内等物体繁杂的地方应用,有非常强的实用价值。     

超宽带SAR未爆物特征提取新方法

超宽带合成孔径雷达(UWB SAR)能够探测浅埋未爆物(UXO),而提取特征的有效性直接决定了检测性能。传统子带-子孔径处理在提取UXO散射函数关于频率和方位信息的同时牺牲了空间分辨率。针对这个问题,该文提出了基于空间-波数分布的频率和方位特征提取方法,并结合不变矩得到具有平移和旋转不变的特征集。该特征集不仅包含了频率和方位信息,而且包含了空间高分辨信息。实测数据处理表明,该文提出的特征能够有效提高UXO检测性能。     

Triangular quad-port multi-polarized UWB MIMO antenna with enhanced isolation using neutralization ring

In this study, a quad-port multi-polarized ultra-wideband (UWB) multiple input multiple output (MIMO) antenna system with a new isolation technique is designed for wireless devices. The antenna structure consists of four triangular monopole elements and neutralization ring (NR) structures. The monopoles are back-to-back positioned in symmetrical and orthogonal arrangement. Therefore, they radiate towards four directions without interference, and thus the diversity performance is improved. A novel NR is formed by combining a rectangular ring and a straight line to reduce the mutual coupling due to interoperation of the elements. Each triangular monopole is fed by 50 Ohm microstrip transmission line (MTL) with a thin strip line for ensuring impedance matching. Antenna performance in terms of impedance bandwidth, current distribution, radiation pattern, peak gain and envelope correlation coefficient (ECC) is also investigated. The MIMO antenna system has 3.1–17.3 GHz impedance bandwidth, 1–5 dBi peak gain variation, less than 0.1 ECC. The results indicate that the proposed antenna has the characteristics of larger UWB bandwidth, high isolation by the NR structure, multi-polarization, uniform gain and quasi-omnidirectional pattern.     

Ultra-wideband balun and power divider using coplanar waveguide to microstrip transitions

An ultra-wideband transition from coplanar waveguide (CPW) to a pair of microstrip lines is presented in this letter. It is shown that the proposed transition can be used to devise an ultra-wideband T-junction power divider with equally split in-phase output signals. More importantly, it is demonstrated that the out-of-phase magnetic currents in the slots of the CPW can be utilized to achieve an out-of-phase power divider or a balun. Both the T-junction power divider and the balun benefit from compact size and good performance over an ultra wide frequency band from 3 to 16 GHz. Prototypes of both proposed devices are fabricated and measured to provide an experimental verification on the concept and numerically predicted features.