| The technique of spaceflight dose very important work to the study of science and the development of economics, and space TT&C is the necessary instrument of technique that insures the normal flight of space shuttle. Because of the condition limits and complex and deteriorated circumstance, it is necessary to adopt the diversity combining to restrain the interference and noise, improve the quality of signal transmission.This paper aims at the special field of space TT&C that different form common mobile communication. And studies the each tache of polarization diversity combining under the deep analysis of the inland and overseas study actuality.Because of the adverse effect of Doppler-shift(frequency offset) that introduced by the reverse movement between the space shuttle and the ground station to the received signal, this paper describes a novel technique for the correction of the Doppler-shift. We analyze this method in theory, and give the system model together with the emulation results.This paper analyzes all the existing techniques of polarization diversity combining, and introduces a S+N(signal-plus-noise) selection arithmetic compared with traditional SNR selection; and gives the material realization and theory analysis, and studies the arithmetic of maximum ratio combining and equal gain combining; and applies MATLAB to give the performance comparison of these three combining modes under the same conditions.In fact, there is relativity between the two branches of the polarization diversity-receiving antenna, so, this paper analyzes the effect of the correlation of the channels to the performance of diversity combining, and gives the method of the generation of the correlated channels. The emulation was used to study the performance. In maximal ratio combining, when each branch's average SNR is relatively small compared to the threshold, our results show that the probability that the output SNR exceeds the given threshold grows as the correlation coefficient increases. |
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