Compared with common near space satellite Telemetry,Telecommand,and Communication(TT&C),deep space TT&C presents a more challenging environment such as long distance,very low Signal to Noise Ratio(SNR).How to ...Compared with common near space satellite Telemetry,Telecommand,and Communication(TT&C),deep space TT&C presents a more challenging environment such as long distance,very low Signal to Noise Ratio(SNR).How to acquire main carrier exactly becomes a hot focus for deep space communications.Already there emerged some main carrier acquisition algorithms,but they all require high SNR and small modulation index.In this paper,we develop a new acquire algorithm.First we use the spectral energy center algorithm to shorten the original sequence,filter out some noise and make the spectral more symmetric.Then we adopt the spectral symmetry algorithm to make full use of the whole spectrum information,and utilize FFT to reduce computation complexity.Simulation results show that our algorithm can acquire main carrier successfully under large modulation index and get good performance with low Carrier to Noise Ratio(CNR).展开更多
在现有的高动态微弱信号的载波跟踪算法中,针对锁频环(FLL)辅助锁相环(PLL)载波跟踪算法,环路调整不连续,易出现跟踪失锁的问题,给出了FLL与PLL的更优组合算法,并确定了组合环路状态转换的过程以及环路状态转换的门限值,从而优化环路性...在现有的高动态微弱信号的载波跟踪算法中,针对锁频环(FLL)辅助锁相环(PLL)载波跟踪算法,环路调整不连续,易出现跟踪失锁的问题,给出了FLL与PLL的更优组合算法,并确定了组合环路状态转换的过程以及环路状态转换的门限值,从而优化环路性能;针对带宽调整不准确影响环路跟踪性能的问题,分析得出最优带宽值,确定了试探法带宽调整策略,对环路带宽进行实时调整,最终在信噪比为3 d B,且存在加加速度分量时,环路的跟踪误差达到3 Hz左右.展开更多
针对锁频锁相器(Phase and Frequency Detector,PFD)应用于低信噪比、大频偏的条件,通过理论分析和仿真验证阐述了窗口类型对系统频偏捕获速度、范围、噪声门限及相位噪声抖动的影响机理.推导出等效相位噪声功率谱密度的表达式.证明了...针对锁频锁相器(Phase and Frequency Detector,PFD)应用于低信噪比、大频偏的条件,通过理论分析和仿真验证阐述了窗口类型对系统频偏捕获速度、范围、噪声门限及相位噪声抖动的影响机理.推导出等效相位噪声功率谱密度的表达式.证明了大窗口具有更低的噪声门限和更小的稳态相位抖动,但捕获速度较慢.为了提高捕获速度,对鉴相器输出值取极性运算得到改进的PFD算法.新算法不仅能增加鉴相增益提高捕获速度;还可以减少等效噪声功率谱密度降低相位抖动;同时新算法不需要乘法器便于硬件实现.最后新算法的性能通过仿真得到了验证.展开更多
基金Supported by the National Natural Science Foundation of China (No. 61032003 and No. 61021001)
文摘Compared with common near space satellite Telemetry,Telecommand,and Communication(TT&C),deep space TT&C presents a more challenging environment such as long distance,very low Signal to Noise Ratio(SNR).How to acquire main carrier exactly becomes a hot focus for deep space communications.Already there emerged some main carrier acquisition algorithms,but they all require high SNR and small modulation index.In this paper,we develop a new acquire algorithm.First we use the spectral energy center algorithm to shorten the original sequence,filter out some noise and make the spectral more symmetric.Then we adopt the spectral symmetry algorithm to make full use of the whole spectrum information,and utilize FFT to reduce computation complexity.Simulation results show that our algorithm can acquire main carrier successfully under large modulation index and get good performance with low Carrier to Noise Ratio(CNR).
文摘在现有的高动态微弱信号的载波跟踪算法中,针对锁频环(FLL)辅助锁相环(PLL)载波跟踪算法,环路调整不连续,易出现跟踪失锁的问题,给出了FLL与PLL的更优组合算法,并确定了组合环路状态转换的过程以及环路状态转换的门限值,从而优化环路性能;针对带宽调整不准确影响环路跟踪性能的问题,分析得出最优带宽值,确定了试探法带宽调整策略,对环路带宽进行实时调整,最终在信噪比为3 d B,且存在加加速度分量时,环路的跟踪误差达到3 Hz左右.
文摘针对锁频锁相器(Phase and Frequency Detector,PFD)应用于低信噪比、大频偏的条件,通过理论分析和仿真验证阐述了窗口类型对系统频偏捕获速度、范围、噪声门限及相位噪声抖动的影响机理.推导出等效相位噪声功率谱密度的表达式.证明了大窗口具有更低的噪声门限和更小的稳态相位抖动,但捕获速度较慢.为了提高捕获速度,对鉴相器输出值取极性运算得到改进的PFD算法.新算法不仅能增加鉴相增益提高捕获速度;还可以减少等效噪声功率谱密度降低相位抖动;同时新算法不需要乘法器便于硬件实现.最后新算法的性能通过仿真得到了验证.
