针对常规波形数字滤波器(wave digital filter,WDF)拓扑结构表达效率低下、结构易混乱的问题,本文利用适配器的可拆分性,提出基于WDF二叉树的拓扑结构表达方法,使等效电路结构清晰直观,从WDF二叉树的形态可迅速获知等效电路的模块并行...针对常规波形数字滤波器(wave digital filter,WDF)拓扑结构表达效率低下、结构易混乱的问题,本文利用适配器的可拆分性,提出基于WDF二叉树的拓扑结构表达方法,使等效电路结构清晰直观,从WDF二叉树的形态可迅速获知等效电路的模块并行度、最长路径等关键信息.此外,本文结合WDF端口适配器的端口对称性,进一步提出WDF二叉树的优化方法.通过对满足要求的结点及附属子叶进行位置交换,令二叉树更为扁平、缩短"入射-反射"过程的最大路径长度,使WDF-FPGA仿真系统的模块并行度和仿真速度得到提升.电路仿真模型优化后的反射步长减少42.86%、入射步长减少38.9%,总运算时间降至0.366ms.展开更多
多主瓣干扰在空时频等维度上与雷达目标回波高度重合,严重削弱了雷达探测性能。针对切片组合(chopping and interleaving,C&I)、间歇采样直接转发干扰、间歇采样重复转发干扰同时并存的问题,提出了一种基于发射波形与接收滤波器联...多主瓣干扰在空时频等维度上与雷达目标回波高度重合,严重削弱了雷达探测性能。针对切片组合(chopping and interleaving,C&I)、间歇采样直接转发干扰、间歇采样重复转发干扰同时并存的问题,提出了一种基于发射波形与接收滤波器联合优化的抗多主瓣干扰方法。首先,基于恒模相位编码信号,构建了C&I、间歇采样直接转发干扰、间歇采样重复转发干扰信号模型。然后,在干扰参数完全已知或者存在偏差条件下,建立了信噪比(signal to noise ratio,SNR)约束下波形相关函数峰值电平、相关函数主瓣模板匹配误差以及干扰能量加权和最小化准则的发射—接收联合优化问题。其次,利用罚函数法、范数转化等方法,将非凸、非光滑并且带约束的优化问题转化成关于自变量(由信号相位、滤波器幅度与相位构成)函数的最小化问题,并利用迭代的限制内存的Broyden-Fletcher-Goldfarb-Shanno(limited-memory Broyden-Fletcher-Goldfarb-Shanno,L-BFGS)算法进行求解。最后,仿真结果表明,该方法设计的优化信号与失配滤波器,具有良好的相关峰值旁瓣电平,能够有效地抑制多主瓣干扰,并一定程度上控制了SNR损失。展开更多
Employing a fiber Fabry-Perot (FFP) interferometer has been considered as a triangle notch filter to demodulate the wavelength of fiber Bragg grating (FBG) sensor.The single parameter of strain has been demodulated,an...Employing a fiber Fabry-Perot (FFP) interferometer has been considered as a triangle notch filter to demodulate the wavelength of fiber Bragg grating (FBG) sensor.The single parameter of strain has been demodulated,and the cross-sensitivity influence of temperature has been eliminated.The principle of this method is simple and easy to be implemented,and has been used to design a 30 t fiber grating weightbridge successfully.The maximal temperature drift error of the weightbridge is 4 με,which means that the full scale error is 8‰. The result reveals that the accuracy is high enough to be used in measurement.展开更多
An algorithm for detecting low-frequency seismic events is developed and applied to the detection of low-frequency events before the 2008 Wenchuan and the 2013 Lushan earthquakes. Continuous vertical-component wavefor...An algorithm for detecting low-frequency seismic events is developed and applied to the detection of low-frequency events before the 2008 Wenchuan and the 2013 Lushan earthquakes. Continuous vertical-component waveforms of some broadband stations in the few months before the Wenchuan and Lushan earthquakes are processed by applying a bandpass filter in 2- 8Hz,and then converted to envelopes with a smoothing time of 10 s window and a median filter with a 20 min window. As a result,teleseismic,long-period noise and local small earthquakes are removed,the filtered amplitude is obviously larger than that of the noise and lasts for a dozen minutes to several hours during a few days in a few stations before the Wenchuan and Lushan earthquakes,respectively. The waveform and envelope are similar to that of a non-volcanic tremor( NVT). There are suspected NVT before the two earthquakes. Preliminary application demonstrates that this algorithm is potentially useful for extracting NVT signals from continuous seismic waveforms.展开更多
文摘针对常规波形数字滤波器(wave digital filter,WDF)拓扑结构表达效率低下、结构易混乱的问题,本文利用适配器的可拆分性,提出基于WDF二叉树的拓扑结构表达方法,使等效电路结构清晰直观,从WDF二叉树的形态可迅速获知等效电路的模块并行度、最长路径等关键信息.此外,本文结合WDF端口适配器的端口对称性,进一步提出WDF二叉树的优化方法.通过对满足要求的结点及附属子叶进行位置交换,令二叉树更为扁平、缩短"入射-反射"过程的最大路径长度,使WDF-FPGA仿真系统的模块并行度和仿真速度得到提升.电路仿真模型优化后的反射步长减少42.86%、入射步长减少38.9%,总运算时间降至0.366ms.
文摘多主瓣干扰在空时频等维度上与雷达目标回波高度重合,严重削弱了雷达探测性能。针对切片组合(chopping and interleaving,C&I)、间歇采样直接转发干扰、间歇采样重复转发干扰同时并存的问题,提出了一种基于发射波形与接收滤波器联合优化的抗多主瓣干扰方法。首先,基于恒模相位编码信号,构建了C&I、间歇采样直接转发干扰、间歇采样重复转发干扰信号模型。然后,在干扰参数完全已知或者存在偏差条件下,建立了信噪比(signal to noise ratio,SNR)约束下波形相关函数峰值电平、相关函数主瓣模板匹配误差以及干扰能量加权和最小化准则的发射—接收联合优化问题。其次,利用罚函数法、范数转化等方法,将非凸、非光滑并且带约束的优化问题转化成关于自变量(由信号相位、滤波器幅度与相位构成)函数的最小化问题,并利用迭代的限制内存的Broyden-Fletcher-Goldfarb-Shanno(limited-memory Broyden-Fletcher-Goldfarb-Shanno,L-BFGS)算法进行求解。最后,仿真结果表明,该方法设计的优化信号与失配滤波器,具有良好的相关峰值旁瓣电平,能够有效地抑制多主瓣干扰,并一定程度上控制了SNR损失。
文摘Employing a fiber Fabry-Perot (FFP) interferometer has been considered as a triangle notch filter to demodulate the wavelength of fiber Bragg grating (FBG) sensor.The single parameter of strain has been demodulated,and the cross-sensitivity influence of temperature has been eliminated.The principle of this method is simple and easy to be implemented,and has been used to design a 30 t fiber grating weightbridge successfully.The maximal temperature drift error of the weightbridge is 4 με,which means that the full scale error is 8‰. The result reveals that the accuracy is high enough to be used in measurement.
基金funded by the National Science & Technology Pillar Program in the 12th "Five-year Plan" Period,China(2012BAKI9B02)
文摘An algorithm for detecting low-frequency seismic events is developed and applied to the detection of low-frequency events before the 2008 Wenchuan and the 2013 Lushan earthquakes. Continuous vertical-component waveforms of some broadband stations in the few months before the Wenchuan and Lushan earthquakes are processed by applying a bandpass filter in 2- 8Hz,and then converted to envelopes with a smoothing time of 10 s window and a median filter with a 20 min window. As a result,teleseismic,long-period noise and local small earthquakes are removed,the filtered amplitude is obviously larger than that of the noise and lasts for a dozen minutes to several hours during a few days in a few stations before the Wenchuan and Lushan earthquakes,respectively. The waveform and envelope are similar to that of a non-volcanic tremor( NVT). There are suspected NVT before the two earthquakes. Preliminary application demonstrates that this algorithm is potentially useful for extracting NVT signals from continuous seismic waveforms.
