| The Beidou-3 satellite navigation system was completed in 2020,the positioning performance and short message performance have been greatly improved,and the service scope has been expanded from the Asia Pacific region to the whole world.Based on the complete retention of Beidou-2 RDSS（Radio Determination Satellite System）inbound and outbound signals,the service adds the new system RDSS inbound and outbound signals.Due to the short construction time,the research on the new system RDSS service signal is still blank.Under this background,this thesis studies the receiving and processing algorithm of the new system RDSS signal,summarizes a set of receiving algorithms for despreading,demodulation and decoding of the new system RDSS outbound signal,and carries out hardware implementation and sensitivity test.The specific work is as follows:According to the modulation characteristics of UQPSK-DSSS with dual pilot branch and data branch,the pilot branch S2C＿p is proposed to performs carrier synchronization and timing synchronization to assist receiving the data branch S2C＿d.After carrier synchronization and timing synchronization,considering that the data branch is divided into common segment signal and special segment signal,and its baseband signal has different rate and channel coding mode,this thesis designs the soft decision coherent demodulation model and the joint iterative model of coherent soft demodulation and channel decoding respectively.Among them,the joint iterative model of demodulation and decoding takes the signal demodulation module and channel decoding module as a whole,which realizes the extraction of soft information during signal demodulation and improves the demodulation performance.At the same time,the effects of symbol signal-to-noise ratio,SISO decoding algorithm,channel coding rate,frame length,iteration times and component encoder on the demodulation performance of the model are analyzed in the simulation.New system pilot signal S2C＿p is an important feature of BDS-3 RDSS communication service,for the reason that S2C＿p branch does not contain message symbols,this thesis proposes to use the four quadrant arc tangent phase detection algorithm as the phase detection algorithm of PLL.Compared with the Costas loop often used in BDS-II receiver,the phase-locked loop using four quadrant arctangent phase detection algorithm has better performance in phase traction range and linear working range,and improves the tracking accuracy.At the same time,aiming at the problem of symbol phase ambiguity in data branch demodulation,a method based on S2C＿p is proposed in this thesis.The detection algorithm of S2C＿p pilot branch has the advantage of low computational complexity compared with the matching search algorithm of single data path signal.The performance of the receiving algorithm is tested.The test results show that for the received signal with signal power of-153 d BW,the bit error rate of the proposed receiving algorithm is less than 10-5,which meets the designed requirements of sensitivity reception.Finally,the reception performance of RDSS service signals during the period of BDS-3 and BDS-2 is compared,and the shortcomings of the reception performance of this paper are analyzed. |
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