The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） re...The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc.展开更多
欧洲空间局的ENVISAT ASAR level 2算法是从合成孔径雷达(SAR)单视复图像反演涌浪方向谱的算法。该算法假设双峰海浪谱的SAR图像交叉谱是涌浪的图像交叉谱和风浪的图像交叉谱之和。实际上双峰海浪谱的SAR图像交叉谱中还有一个混合项,正...欧洲空间局的ENVISAT ASAR level 2算法是从合成孔径雷达(SAR)单视复图像反演涌浪方向谱的算法。该算法假设双峰海浪谱的SAR图像交叉谱是涌浪的图像交叉谱和风浪的图像交叉谱之和。实际上双峰海浪谱的SAR图像交叉谱中还有一个混合项,正是该混合项导致ENVI-SAT ASAR level 2算法有固有误差。利用遥感仿真的方法分析了不同海况条件下该算法的这一固有误差,结果表明,只有在有效波高较小、或风浪的成分较少、或双峰海浪的传播方向较靠近SAR距离向、或波长较长时固有误差才较小,ENVISAT ASAR level 2算法对海浪谱的反演才较为适用。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 60977005)
文摘The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc.
文摘欧洲空间局的ENVISAT ASAR level 2算法是从合成孔径雷达(SAR)单视复图像反演涌浪方向谱的算法。该算法假设双峰海浪谱的SAR图像交叉谱是涌浪的图像交叉谱和风浪的图像交叉谱之和。实际上双峰海浪谱的SAR图像交叉谱中还有一个混合项,正是该混合项导致ENVI-SAT ASAR level 2算法有固有误差。利用遥感仿真的方法分析了不同海况条件下该算法的这一固有误差,结果表明,只有在有效波高较小、或风浪的成分较少、或双峰海浪的传播方向较靠近SAR距离向、或波长较长时固有误差才较小,ENVISAT ASAR level 2算法对海浪谱的反演才较为适用。
文摘【目的】超宽带测距误差分布表明,在存在显著重尾的情况下,高斯混合模型比简单的高斯概率包络更接近经验分布。通过传统的超界分布(Overbounding Distribution)模型获得的保护水平过于保守,会降低系统可用性。【方法】为提高系统可用性,提出了基于高斯混合模型(GMM)的超界框架来处理基于TOA(Time of Arrival)定位的超宽带测距误差样本。首先,结合EM算法获得测距误差的双组分GMM概率密度函数,并修正边界参数,使左右边界均满足双边超界条件,以构建双组分GMM形式的距离域双边超界模型。随后,基于GMM双边超界模型推导出计算位置域保护级(PL)的方法,对距离域的概率密度函数进行卷积以获得位置概率密度函数,求逆运算出PL。【结果】最后,开展实验验证应用GMM双边超界模型收紧PL的效果,采集3~93 m范围内的样本数据用于误差模型的构建,真实测试的性能评估表明,基于GMM双边超界模型比传统高斯双边超界模型计算所得的PL减小了20%以上。【结论】GMM双边超界模型能够以较小的计算成本收紧PL,增强系统可用性。
