| This paper first introduces the background and significance of the research, and briefly illustrates the application of high-speed modulation in the satellite broadband wireless data transmission. Based on the brief introduction of the most widely applied principle of space-borne modulation techniques, this paper makes a profound and comparative study on modulation principle and transmission theory of 8PSK、16APSK、16QAM及32APSK, determines the overall scheme of high order modulation technology with digital modulation as its core.Then, taking the digital modulation scheme for the foundation, through the ADS software system modeling, mainly in 8PSK、16APSK、16QAM and 32APSK modulator, combined with the characteristics of satellite communication AWGN channel, the system amplifier nonlinear、the modulation of the amplitude imbalance、pass band ripple and phase noise of the whole system is simulated and analyzed.LDPC characteristics of CCSDS presents is simulated and analyzed in this paper, according to the coding characteristics, proposed high-speed parallel processing method of the code, build the simulation system of LDPC with high order modulation, using LDPC code obtained coding gain, characteristics of the LDPC+APSK and LDPC+QAM were compared, different higher order modulation of the system channel characteristics is obtained.Combining with the AWGN characteristics of the wireless channel, the system modeling, Derived using the LDPC code,the amplifier nonlinear、modulator amplitude unbalance、pass band ripple、and phase noise of transmission, theoretical basis for loading system modulation and coding method for star combination scheme.Finally, the practical circuit design, Ka band modulator composition and realization method are、introduced in detail, the key indicators are decomposed, and comparing the measured results and simulation results, that scheme is correct. |
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