Reserch On Key Technologies Of Inter Satellite Links For Distributed Satellites System

Inter-satellite Data transmission, inter-satellite ranging, inter-satellite time synchronization and wireless networking technology with the inter-satellite links are four important part of the distributed satellite system, which are regarded as key technologies in the field of payload collaborative work, having become the cutting-edge research in the field of distributed satellite system. Considering the weight, volume and power consumption of a single satellite in the distribute satellite system is strictly limited, this paper mainly studies a system capable of simultaneously transmitting high rate telecommunication and ranging, named Gaussian minimum shift keying + pseudo-noise(GMSK+PN).In this paper, the GMSK+PN modulation and demodulation methods are deeply studied, including the modulated signal characteristics analysis, the modulation parameters setting, the demodulation of GMSK, the separation among GMSK, ranging signal and the demodulation of ranging signal, etc.. The following aspects are specifically completed:? The simulation analysis of GMSK+PN modulation and demodulation algorithm is carried out. On the basis of the simulation, the FPGA hardware platform obtains valid measurement result, which verifies the effectiveness of the modulation and demodulation algorithm. For the demodulation of GMSK+PN, an effective scheme for GMSK and PN ranging information separation is proposed.? A simplified algorithm is proposed to estimate the signal to noise ratio of GMSK+PN signal. The GMSK+PN signal is modeled according to its characteristic. Calculation of the various signal components in the composite signal proportion simplifies signal model layer by layer, and the signal to noise ratio of the synthesized signal is estimated at last. The feasibility of this algorithm is proved by the simulation analysis.? Based on the distributed algorithm and polyphase decomposition method,this paper presents a new algorithm in implementation of high order FIR filter in existing FPGA, which reduces hardware resources consumption significantly, and gives the filter performance under the condition of different quantization bits width.? According to the digital sources with different rates and different burst time slot, a design scheme of a greedy asynchronous dynamic digital multiplexer is proposed. The priority scheduling strategy of sources is also demonstrated. The results of the simulation comparison show that, for the average transmission delay, delay jitter and packet maximum delay, the greedy dynamic multiplexing is superior to the virtual channel multiplexing, and is more effective in saving resource of source cache.The research work of this paper, lay a good foundation for the realization of collaborative technology, wireless networking technology, emergency response and other application requirements of the distributed satellites system.