In this paper, multipath temporal spreading distributions of laser pulses are calculated when they travel through the seawater. Individual photon is followed in Monte Carlo calculation A modified Henyey-Greenstein （H...In this paper, multipath temporal spreading distributions of laser pulses are calculated when they travel through the seawater. Individual photon is followed in Monte Carlo calculation A modified Henyey-Greenstein （HG） function is applied to represent the scattering phase function of seawater. This paper proposes a new scaling method, which uses the effective scattering thickness τd to replace the optical thickness used in the traditional scaling technique. This paper compares the temporal spreading distributions of photons on conditions of different attenuation coefficients and target depths. The experiments reveal that these mutual deviations are changing in the range from 0.5% to 5%, so long as the corresponding effective scattering thicknesses τd remains the same. Therefore, a conclusion can be obtained, that the temporal spreading distribution is only dependent on the effective diffusion thickness τd .展开更多
分析无线信号在不同环境下的信道传播特性常用的方法有统计学建模法和实际测量法,其中,实际测量法需要借助专业的测量工具。针对无线信道传输特性分析的实际需求,利用基于扩频滑动相关方法来获取信道冲激响应的原理,分析了4种常用伪随...分析无线信号在不同环境下的信道传播特性常用的方法有统计学建模法和实际测量法,其中,实际测量法需要借助专业的测量工具。针对无线信道传输特性分析的实际需求,利用基于扩频滑动相关方法来获取信道冲激响应的原理,分析了4种常用伪随机序列的相关特性,提出利用恒包络零自相关(Constant Amplitude Zero Auto-Correlation,CAZAC)序列进行冲激响应测量的基本方法并搭建了系统架构,然后设计了无线信道特性实时探测系统。最后,通过多通道信道模拟器验证了设计系统的可靠性,并通过室内和室外的实测验证了所提方法的有效性和系统设计的可行性。展开更多
该文分析了天波超视距雷达(Over The Horizon Radar,OTHR)多径扩展多普勒杂波(Spread Doppler Clutter,SDC)的产生机理。由于阵列存在幅相误差且期望信号的功率大于SDC功率,自适应数字波束形成(Adaptive Digital Beam Forming,ADBF)将降...该文分析了天波超视距雷达(Over The Horizon Radar,OTHR)多径扩展多普勒杂波(Spread Doppler Clutter,SDC)的产生机理。由于阵列存在幅相误差且期望信号的功率大于SDC功率,自适应数字波束形成(Adaptive Digital Beam Forming,ADBF)将降低SDC抑制能力,同时还会导致信号对消,严重降低信噪比。针对以上问题,该文提出一种自适应抑制SDC的方法。该方法首先采用改进噪声子空间拟合自校正法消除阵列幅相误差,得到期望信号和SDC准确的到达仰角,然后采用正交投影权矢量进行ADBF处理,避免了强期望信号条件下ADBF权矢量估计不准的问题。理论分析和仿真实验表明该方法能够较彻底地抑制多径SDC。展开更多
基金Supported by the National Natural Science Foundation of China (60572015)
文摘In this paper, multipath temporal spreading distributions of laser pulses are calculated when they travel through the seawater. Individual photon is followed in Monte Carlo calculation A modified Henyey-Greenstein （HG） function is applied to represent the scattering phase function of seawater. This paper proposes a new scaling method, which uses the effective scattering thickness τd to replace the optical thickness used in the traditional scaling technique. This paper compares the temporal spreading distributions of photons on conditions of different attenuation coefficients and target depths. The experiments reveal that these mutual deviations are changing in the range from 0.5% to 5%, so long as the corresponding effective scattering thicknesses τd remains the same. Therefore, a conclusion can be obtained, that the temporal spreading distribution is only dependent on the effective diffusion thickness τd .
文摘分析无线信号在不同环境下的信道传播特性常用的方法有统计学建模法和实际测量法,其中,实际测量法需要借助专业的测量工具。针对无线信道传输特性分析的实际需求,利用基于扩频滑动相关方法来获取信道冲激响应的原理,分析了4种常用伪随机序列的相关特性,提出利用恒包络零自相关(Constant Amplitude Zero Auto-Correlation,CAZAC)序列进行冲激响应测量的基本方法并搭建了系统架构,然后设计了无线信道特性实时探测系统。最后,通过多通道信道模拟器验证了设计系统的可靠性,并通过室内和室外的实测验证了所提方法的有效性和系统设计的可行性。
文摘该文分析了天波超视距雷达(Over The Horizon Radar,OTHR)多径扩展多普勒杂波(Spread Doppler Clutter,SDC)的产生机理。由于阵列存在幅相误差且期望信号的功率大于SDC功率,自适应数字波束形成(Adaptive Digital Beam Forming,ADBF)将降低SDC抑制能力,同时还会导致信号对消,严重降低信噪比。针对以上问题,该文提出一种自适应抑制SDC的方法。该方法首先采用改进噪声子空间拟合自校正法消除阵列幅相误差,得到期望信号和SDC准确的到达仰角,然后采用正交投影权矢量进行ADBF处理,避免了强期望信号条件下ADBF权矢量估计不准的问题。理论分析和仿真实验表明该方法能够较彻底地抑制多径SDC。
