Research On Parallel Demodulation Techniques Of High Data-rate Satellite Signal

Modulation and demodulation techniques are key techniques of satellite data transmission system, so, research on high-speed digital modulation and demodulation techniques has great meaning for high-speed data transmission system. However, with the constraints of algorithm complexity and the performance of digital components, it is difficult to realize real-time demodulation of high-speed signal. Parallel demodulation is proposed to solve this problem. Based on this, the main work and achievements of this thesis are summarized as follows:A model of parallel demodulation is designed. By parallel demodulation, data rate is reduced, thus the performance requirements of the algorithm and the digital components are reduced. It is composed of data distributing, baseband signal demodulation, recoding, data recovery, recoding recovery.For timing recovery, based on Gardner algorithm and the highest average power algorithm, considering the characteristics of parallel demodulation, parameter transfer is put forward. With little increase in computation, the algorithm gets faster loop convergence, and the initial timing error is reduced. Parameter transfer accelerates the convergences and reduces the bit error rate of the initial data and meets the requirements of the parallel demodulation better.For carrier recovery, considering the parallel demodulation, based on the tradition carrier recovery loop, a structure of parameter transfer of loop filters is proposed. The capture time becomes shorter and the bit error rate of the initial data is reduced. Therefore, the performance of the system is improved.For digital automatic gain control(AGC), based on analysis and simulation, similar to the carrier recovery, the parameter transfer is applied in the integrators of AGC loops. As a result, signal average power converges faster, and signal amplitude is regulated better.For parallel data distributing and recovery, the scheme distributing data by data wrapping and recovering data by data matching is put forward. What's more, in order to solve the problem of different phase ambiguity in different routes, a new method called recoding is proposed to solve the problem simply and effectively.After studying and improving every units of the model, a FPGA-base implementation scheme is presented. Comprehensive debugging is carried out successfully. Demodulation test results targeting at real-time signals generated from Agilent E8267D have proved the validity of the whole system.