Research On Signal Acquisition Algorithm Of GNSS Dual Frequency Compatible And Interoperable Receiver

The user receiver is an important part of the Global Navigation Satellite System(GNSS)and a key hub for satellite positioning and navigation.Designing a dual-band compatible interoperable receiver allows the receiver to function better and perform better.The role of signal acquisition is to roughly estimate the carrier doppler shift and code phase offset of the received signal,since the dual-frequency compatible interoperable receiver can receive multiple types of signals,which puts certain requirements on the design of the acquisition algorithm.This topic comes from the "GNSS dual-frequency compatible interoperable receiver research and development" project.The receiver developed by the project has three working modes: single frequency compatible interoperable mode,dual frequency compatible interoperable mode and single signal working mode.It can receive 8 kinds of signals,respectively: B1 I signal,B1 C signal,B2 a signal,L1C/A signal,L1 C signal,L5 Signal,E1 OS signal,E5 a signal,and each kind of signals is different in modulation mode and structural characteristics.This topic focuses on the research and design of the receiver's capture module in this project.In order to solve the problems like the multi-type signal acquisition methods' not uniform,the capture performance's not up to standard,the processing process' s cumbersome,and the implementation cost's high.This topic designed a capture algorithm for multiple types of signals,it is based on FFT-based parallel code phase acquisition algorithm.First of all,the IF signal is sampled at a sampling rate,which is twice the code rate.Then,the algorithm combines the two samples from the first sample to generate 0 phase branch data and from the second sample to generate 1 phase branch data.The two branchs of data are correlated with the local pseudo code.After,according to the characteristics of the signal,the two correlation results are respectively subjected to multiple coherent accumulation and non-coherent accumulation to obtain a plurality of non-coherent accumulated peaks.If the peak value exceeds the capture threshold,the signal exists.Finally,by analyzing the position information of the maximum peak,the Doppler frequency offset and code phase offset of the signal can be obtained.For signal acquisition including pilot components and data components,the receiver only needs to provide two receiving channels,and the two algorithms are processed separately by the above algorithm.The only difference is that after the two components complete their respective non-coherent accumulation operations,a non-coherent accumulation operation is performed again to realize the combination of the two-component non-coherent accumulation results.The project uses the verilog language to design and implement the algorithm in the Vivado2016.2 development environment,and carries out multi-faceted analysis and performance verification of each signal acquisition process and results.After analysis and demonstration andengineering realization,the proposed algorithm can capture 8 kinds of signals,and the capture performance meets the receiver design requirements.