UWB无线传感器网络中基于匹配滤波检测的TOA估计

深入研究了UWB(ultra wideband)无线传感器网络中基于匹配滤波门限检测的TOA(time of arrival)估计算法.针对现有算法的不足,提出了一种三步TOA估计算法:先确定DP(direct path)搜索区域,然后使用门限检测确定DP的粗略位置,最后精确搜索到DP的中心.其中,用于计算检测门限的门限因子依据匹配滤波输出的峭度动态设置,设置模型独立于信道模式,其正确性通过与使用固定门限因子所获得的性能对比进行了验证.与其他算法的性能对比仿真结果表明,所提出的三步TOA估计算法在运算效率和TOA估计精度上取得了较好折衷,适合于当前实际应用.还通过对TOA估计误差的统计分析讨论了测距结果的可信度:依据峭度将测距结果划分为可信和不可信两个级别,并为各级别的TOA估计误差分别了建立概率密度模型.在定位模块中有效利用这些可信度信息,可进一步提高定位精度.     

基于机载光电成像系统光学铰链离轴的伺服抗扰算法设计

在小型化机载光电成像系统中,光学铰链与伺服框架轴非正交的离轴设计,给光轴指向控制及卸载飞机扰动的稳定控制带来了一定的困难。为了解决这一问题,系统控制回路采取半捷联设计,通过使用经微分处理后的伺服框架角信号,与叠加了经抗扰算法处理的飞机载体三轴角速度信号共同作为稳定回路的期望值,再进行匹配滤波。对比采用陀螺信号反馈的直接稳定控制回路具有相似的稳定精度。     

Effects of transmitter-related parameter settings on ranging accuracy for IR-UWB systems

For impulse radio ultra-wideband (IR-UWB) ranging systems,effects of the settings of transmitter-related parameters, which include the pulse shape, the bandwidth and the pulse repetition interval (PRI), on ranging accuracy were studied through theoretical analysis and simulations. Both the match-filtering based coherent TOA estimation algorithm and the energy-detection based non-coherent algorithm were used during simulations. Results show that the pulse shape has the least effect on the ranging accuracy. Increasing the pulse bandwidth can improve the ranging performance, but the performance is hardly improved any more when the bandwidth is increased beyond a certain level. PRI should be set long enough to guarantee the accurate ranging, because when PRI is shorter than the maximum excess delay of the channel, the ranging accuracy will be deteriorated by inter-pulse interference.