| Ranging technology is one of the key technologies of New Ground-based Navigation system.The accuracy of ranging determines the time synchronization precision inter stations of GBNB and the positioning accuracy of user receivers.As the baseband signal processing is the fundamental goal of ranging receiver,two aspects have carried out as follows:1.The acquisition technology of TH/DS-CDMA signal is investigated.A digital match filter based on fast convolution is presented and the computational complexity is optimized.The THSI search algorithm has no tolerance to the leaking alarming of burst CDMA signal acquisition.Thus an improved algorithm is presented to overcome the shorting of it,improving the synchronization probability of the time-hopping sequence under low carrier-to-noise.Based on the delay consistency of four ranging code signals,a joint acquisition algorithm with more than 4dB non-coherent integration gain when C/N0≥44dB·Hz is proposed for burst CDMA signal acquisition.2.The tracking technology of TH/DS-CDMA signal is investigated.A PLL with time-varying sampling period is proposed,and stability analysis is carried out according to the Lyapunov stability theorem.The calculation formula of noise bandwidth for the1-3 order DPLL is given.Based on the delay consistency of four ranging code signals,a joint DLL is proposed.Compared with the independent DLL,the joint DLL provides that code phase measured accuracy doubled.Vector tracking is attracting more and more attention,and would be one of the key technologies used by the next generation receiver.This paper proposes the mathematical proof that the accuracy of the VDLL is better than the conventional DLL.WhenC/N0≥55dB·Hz,the precision of the ranging code phase is better than0.12m,the precision of single difference of caerrier phase is better than 0.82mm.The testing results show the ranging performance of the receiver degined in this paper is superior to the Locata's receiver. |
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