Research Of The X-ray Space Communication System

At present, the range of electromagnetic spectrum used in space communications isexpanding. The new concepts and new technologies which used the X-ray band ofelectromagnetic waves in space communications have been proposed in recent years. Atabroad, the substantive research in this area is limited to the astrophysicist Dr.Keith andhis team, he come from National Aeronautics and Space Administration (NASA) ofUnited Stated. In china, the scientists of Xi’an Institute of Optics and PrecisionMechanics of Chinese Academy of Sciences proposed the new concept that used theX-ray in space communications at the first time, and set up the digital transmission ofthe X-ray verification system based on voice communications. This study also attractedthe attention and coverage of the Chinese Science Times. Carry out the study of theX-ray space communications systems has a vital role for china and play a verysignificant role in promoting our country to research the cutting-edge direction in theword.In this paper, on the basis of research the principle and the research status with theoptical communication at home and abroad. The advantages and disadvantages havebeen combined with which exist in the X-ray communication system proposed byDr.Keith Gendreau, a new program of the X-ray communication have been proposed.This system mainly consists of the X-ray emission source, the composition of the X-rayreceiver, signal demodulation electronics. Among them, X-ray emission source usinggated X-ray emission tube to solve the shortcomings in the transmit power of KeitheGendreau’s program, using the X-ray with microchannel plate which have the capabilityof single photon detection, through this detector, the weak X-ray signal can beendetected, the signal demodulation electronics is achieved by the number ofsignal-photon pulse.For the X-ray detector used in the experimental system, a new method of signalphoton counting have been proposed, and measure the measure the minimum detectablepower of the detector under the mode of the photon counting. Through to establish asimple mode the of the X-ray transmission in the space and the known minimum detectable power of X-ray detector, the relationship between the X-ray transmissiondistance and the transmit power of the X-ray emission source have been obtained.Through the analysis of the signal demodulation method of the opticalcommunication system and combined with the signal characteristics of the X-raycommunication method, three different signal demodulation method used the density ofthe photon pulse have been designed: pulse envelope detection demodulation method,photon pulse count demodulation method and photon re-trigger demodulation method.The experimental results waveform has been obtained after the signal demodulate.Through to analysis of the waveform in the different X-ray emission power, theexperimental results show that increase the X-ray emission power can improved thetransmit data baud rate. Carry out the communication experiment at three differentdemodulation method using the serial debugging little helper respectively, and analysisof the communication error rate using three different demodulation method at differenttransmission rate. The experimental results show: when using the pulse envelopedetection demodulation method, the communication error rate is0when thetransmission rate is lower than1200bit/s, the communication error rate is0.5%whenthe transmission rate is1200bit/s; when using the photon pulse count demodulationmethod, the communication error rate is0when the transmission rate is2400bit/s, thecommunication error rate is1.9%when the transmission rate is4800bit/s; when usingthe photon re-trigger demodulation method, the communication error rate is0when thetransmission rate is14400bit/s, the communication error rate is11.8%when thetransmission rate is34800bit/s. Therefore, when using the photon re-triggerdemodulation method, the transmission rate can improved greatly.