Theory Research And Engineering Realization Of Spaceborne GMSK Modulator

With the rapid development of satellite communication system,the dwindling frequency bandwidth resources and the characteristics of band channel put forward the new request to the modulation technology, the traditional modulation has not fully meet these requirements, this paper presents a new modulation technology-- GMSK modulation.This paper firstly introduces several kinds of new modulation technology in the modern satellite communication, including BPSK, QPSK, 2FSK, MSK and GMSK modulation technology, and describes various of modulation implementation ways in details.Then, this paper gives the design scheme of spaceborne GMSK modulator.Considering the strict requirements to spaceborne GMSK modulator index, implementation mode of function adopts integral phase shift keying. The output of interface circuit received from an external I、Q two baseband data, conducts LDPC code and Gauss filtering. Later, the data through rate conversion,DA transform and level conversion sends to the direct modulation circuit of RF microwave. The design of scheme uses memory look-up table method in Ganss filtering segment. The value of cos[Φ(t)] and sin[Φ(t)] computed and storaged is lookup by address, then calculates quadrant, Ganss filter function accomplishs.This paper completes the design of hardware and software, At the same time, the design is modeled and simulated using the MATLAB software. This paper completes the device selection of FPGA、DAC and integrated operational amplifier. At the same time, by providing design input, this paper accomplishes PCB machining 、 assembling and debugging,delivers the indicators qualified engineering prototype.In view of the spaceborne GMSK modulators is different from the ground equipment,during the process of design, satellite product reliability and use environmemtal requirements are considered. The performance test of prototype output spectrum test, a large number of experiment and access system analysis, verify the correctness of design scheme and the feasibility of the engineering actualization.