| X-ray pulsar navigation is a new method of autonomous navigation used in deep space. It has obvious advantages of good reliability, high accuracy and strong anti-interference capacity in deep space navigation. It’s hard for X-ray to penetrate the earth’s atmosphere, and Xs-ray can hardly be detected in ground. And it’s necessary to build ground simulation system for X-ray pulsar autonomous navigation. Thus, it is a key task to solve those problems in X-ray pulsar navigation.Based on the analysis of modulated X-ray source, grid controlled X-ray tube is used as generator of X-ray pulsar simulated source in this paper. According to X-ray pulsar simulated source and grid tube’s characteristic curve, mathematic model of analog modulation and digital modulation have been built by the method of direct digital frequency synthesis (DDS) and pulse width modulation technique. Driving by arbitrary signal generator and high voltage power supplies, X-ray pulsar source is simulated very well in pulse profile and intensity.Performance of X-ray pulsar simulated source is evaluated by time correlation coefficient and frequency correlation coefficient. In this paper, performance of simulation source has been evaluated by pulsed fraction pf and half-width half maximumW with time correlation coefficient and frequency correlation coefficient. And simulation source has been evaluated well in this way.The properties of Crab pulsar simulation source are tested very well in X-ray simulation experiment system. The results of the test are as following:comparing with tested pulse profile and standard pulsar profile, time correlation coefficient is0.9774, and frequency correlation coefficient is0.9853.The X-ray phonon flux Fx is1.90ph.cm-2.s-1,23%higher than before. The pulsed fraction pf is76.15%,6.15%higher than before. The half-width half maximum W is1.879ms,13%higher than before.X-ray pulsar simulated source has been designed in this paper. The researches of this paper are very important. Firstly, problems of pulse profile similarity and phonon flux have been solved. Secondly, based on direct digital frequency synthesis (DDS) technology, grid-controlled signal profile and digital sequences have been got in simulation source. And it has provided an effective platform for high stability clock system of simulation source. Thirdly, the researches have proved a solid foundation for developing a high-performance simulation source. Finally, it has provided guarantee for integrating X-ray pulsar navigation simulation experiment system in ground, and advances the study of X-ray pulsar autonomous navigation. |
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