X射线通信系统的误码率分析

基于栅极控制脉冲发射X射线源与单光子探测技术的X射线通信语音方案已经在实验室实现, 为探索未来X射线深空通信应用打下了坚实的基础. 实验室X射线语音通信演示系统实现后, 迫切需要测试X射线通信系统的误码率性能. 在泊松噪声模型下对X射线通信演示系统的理论分析的基础上, 使用基于现场可编程门阵列的误码率测量方法对开关键控调制方式下X 射线通信误码率进行测量. 通过实验测量发现, 要实现语音通信, 系统误码率应该达到10^-4 量级; 分析、测量了现有系统在开关键控调制方式下不同速率对应的误码率, 论证了泊松噪声模型理论分析现有X射线通信系统的合理性; 分析提出了限制现有实验室条件下X 射线通信误码率性能的主要因素.

Bit error rate analysis of X-ray communication system

X-ray communication, which was firstly introduced by Keithe Gendreau in 2007, is potential to compete with conventional communication methods, such as microwave and laser communication, against space surroundings. As a result, a great deal of time and effort has been devoted to making the initial idea into reality in recent years. Eventually, the X-ray communication demonstration system based on the grid-controlled X-ray source and microchannel plate detector can deliver both audio and video information in a 6-meter vacuum tunnel. The point is how to evaluate this space X-ray demonstration system in a typical experimental way. The method is to design a specific board to measure the relationship between bit-error-rate and emitting power against various communicating distances. In addition, the data should be compared with the calculation and simulation results to estimate the referred theoretical model. The concept of using X-ray as signal carriers is confirmed by our first generation X-ray communication demonstration system. Specifically, the method is to use grid-controlled emission source as a transceiver while implementing the photon counting detector which can be regarded as an important orientation of future deep-space X-ray communication applications. As the key specification of any given communication system, bit-error-rate level should be informed first. In addition, the theoretical analysis by using Poisson noise model also has been implemented to support this novel communication concept. Previous experimental results indicated that the X-ray audio demonstration system requires a 10^-4 bit-error-rate level with 25 kbps communication rate. The system bit-error-rate based on on-off keying (OOK) modulation is calculated and measured, which corresponds to the theoretical calculation commendably. Another point that should be taken into consideration is the emitting energy, which is the main restriction of current X-ray communication system. The designed experiment shows that the detected X-ray energy is 7×10^-5 mW/m². This relatively low power level not only restricts the bit rate of transceiver, but also increases the error fraction to some extent. Obviously, OOK modulation can meet the high communication rate and relatively low bit-error-rate requirement of current audio demo system. Current restriction has been pointed out and the potential improvement is also presented.