光子学报, 2017, 46 (10): 1035001, 网络出版: 2017-11-24
空间X射线通信链路建模与功率分析
Space X-ray Communication Link Modeling and Power Analysis
X射线通信 链路模型 功率方程 单光子探测 误码率 X-ray communication Link model Power equation Single photon detection Bit error rate
摘要
从空间X射线通信传输理论出发, 首先对X射线通信的功率传输过程进行研究, 以加性高斯白噪声信道模型与自由空间损耗为基础, 分析了深空X射线通信的信道特征及功率传输过程、推导了功率传输方程, 建立了通信链路模型; 其次, 分析了深空X射线通信系统的误差来源, 建立了基于单光子探测器的噪声模型, 并给出了主要噪声来源的数学表达式, 从而确定了通信核心参数通信距离、通信速率、误码率与信号功率之间的关系; 最后, 对不同阳极高压与不同调制方式下探测器端信号光子数进行实验监测, 对功率传输方程及误差模型进行验证.实验结果表明, 所给出的功率传输方程与误差模型可以对空间X射线通信过程进行较好地解释.根据此模型, 计算了在满足一定的误码率和传输距离要求时对X射线源出射功率的要求, 为空间X射线通信研究建立了理论基础, 为核心元器件的研究指明了下一步的方向, 同时有望对空间X射线通信的工程化提供一定的参考.
Abstract
X-ray communication(Xcom) is a method which applying X-ray as carriers to transmit information in space. After the concept of Xcom was produced by Dr Keith, many institutions and scientists have conducted researches on Xcom and achieved fruitful results. However, most researches are focused on the key devices of Xcom, such as the X-ray emit source, the antenna and the detector, there is nearly no theoretical model for space X-ray communication. In this article, we focused on the power transmission process of space Xcom. To begin with, we analysised the signal channel and transmission model based on the additional gussian white noise(AWGN) model and free space attenuation, established the power transmission equation and link model. Then we analysised the error source of Xcom, established the noise model based on single photon detectors and also given the main noise sources. In other words, we can built mathematical relationship between the power of X-ray source, transmitting distance&speed and bit-error-ration (BER). Finally, we testified the signal photons of Micochannel Plate(MCP) detector output against various anode voltage and modulations. The results accord well with the theoretical analysis, and the power transmission equation and BER model can explain the Xcom process well too. Based on this transmission theory, we can calculate the emit X-ray power against various transmission distance and BER level respectively. As a result, three key parameters which judging a wireless optical communication system have been given as well as the theoretical model. Simulation results showed that with a constant photons flow, Pulse Position Modulation(PPM) has a better BER level than On-Off Keying(OOK) modulation. When the transmission distance is about 10 km, in order to achieve BER less than 10-6 level, the power consumption of X-ray is less than 1mW. According to the power transmission model, in order to improve the BER level of Xcom system, we need a lower dark current detector, an advanced modulation and more transmitting power. These theoretical and experiment results could provide foundations for optimizing the core parameters of XCOM system in our future works.
苏桐, 李瑶, 盛立志, 强鹏飞, 陈琛, 徐能, 赵宝升. 空间X射线通信链路建模与功率分析[J]. 光子学报, 2017, 46(10): 1035001. SU Tong, LI Yao, SHSNEG Li-zhi, QIANG Peng-fei, CHEN Chen, XU Neng, ZHAO Bao-sheng. Space X-ray Communication Link Modeling and Power Analysis[J]. ACTA PHOTONICA SINICA, 2017, 46(10): 1035001.