The Analysis And Research Of Modulations In Deep Space Communications

The channel of deep space communication is described to be the typical band-limited and non-linear channel. Basing on its special characteristic, we have the principles to select a type of modulation techniques for deep space communication systems .By theory and practice simulation, several types of constant envelope modulation techniques are analyzed and compared, including their modulation principle, the modulated wave envelope, power spectrums density, error bit rate and the influence of the band-limited and non-linear channel on its power spectrums, etc.Especially we have researched the IJF-OQPSK modulation technique, and the performance of its inter-symbol interference and time jitter free, and its strongly resisting of spectral. But it has 3dB envelope undulation. FQPSK avoids this defect. We simulate its power spectrums density and error bit rate. We also research the performance of SOQPSK and improved SOQPSK modulation.