The double Rayleigh backscatter （DRB） effect in long distance CATV systems using fiber Raman amplifiers （FRAs） is investigated theoretically in the paper. As a comparison, performance of a system with erbium doped...The double Rayleigh backscatter （DRB） effect in long distance CATV systems using fiber Raman amplifiers （FRAs） is investigated theoretically in the paper. As a comparison, performance of a system with erbium doped fiber amplifier （EDFA） is also evaluated. According to the simulation results, it is found that, in case of FRA, the increase of carrier-to-noise ratio （CNR） due to the DRB effect will not impair the performance more than that using EDFA.展开更多
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
本文从随机共振(Stochast ic Resonance)可增强信号信噪比的现象出发,介绍了随机共振非线性双稳势阱模型和参数调节随机共振理论。在此基础上,分析了随机共振现象在微弱信号接收中两种可能的应用途径,通过仿真验证了应用的可行性。最后...本文从随机共振(Stochast ic Resonance)可增强信号信噪比的现象出发,介绍了随机共振非线性双稳势阱模型和参数调节随机共振理论。在此基础上,分析了随机共振现象在微弱信号接收中两种可能的应用途径,通过仿真验证了应用的可行性。最后,分析提出了将随机共振理论应用于弱信号接收需要突破的三大关键技术,即:大参数信号变尺度与还原技术、参数自适应调节技术和调制信号随机共振技术,还提出了初步解决的思路。为拓宽随机共振现象的应用领域和探究解决低信噪比条件下的信号接收提供新的方法和途径。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.61077018)the Shanghai Leading Academic Discipline Project (Grant Nos.S30108, SKLFSO200901)
文摘The double Rayleigh backscatter （DRB） effect in long distance CATV systems using fiber Raman amplifiers （FRAs） is investigated theoretically in the paper. As a comparison, performance of a system with erbium doped fiber amplifier （EDFA） is also evaluated. According to the simulation results, it is found that, in case of FRA, the increase of carrier-to-noise ratio （CNR） due to the DRB effect will not impair the performance more than that using EDFA.
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).
文摘本文从随机共振(Stochast ic Resonance)可增强信号信噪比的现象出发,介绍了随机共振非线性双稳势阱模型和参数调节随机共振理论。在此基础上,分析了随机共振现象在微弱信号接收中两种可能的应用途径,通过仿真验证了应用的可行性。最后,分析提出了将随机共振理论应用于弱信号接收需要突破的三大关键技术,即:大参数信号变尺度与还原技术、参数自适应调节技术和调制信号随机共振技术,还提出了初步解决的思路。为拓宽随机共振现象的应用领域和探究解决低信噪比条件下的信号接收提供新的方法和途径。
