The Research And Realization On The Carrier And Timing Synchronization Method In Communication Digital Receiver

With the development of digital communication technology,application scenario of communication system becomes more and more complex.In many applications,the accepted IF signal of digital communication system always exists the interference of frequency offset,which make the receiving terminal have the problems of demodulation error,owing to the influence of Doppler frequency offset.Moreover,because of the clock deviation existing the sampling clock crystal oscillator between the sending terminal and the receiving terminal of the digital communication system,it makes the receiving terminal have the problems of sampling rate deviation,which will put forward higher requirements of receiving terminal of digital communication system,and the core technology to solve this problem is the synchronization technology.This paper conducts the research on the synchronization technology in the digital communication system for the above problems,and it carries out the improvement on carrier synchronization and timing synchronization technology to gain new methods.The main work of this paper includes the following aspects:(1)The traditional carrier synchronization technology is studied deeply including square loop,Costas loop and so on,its advantages and disadvantages.An improved digital Costas loop is put forward on this basis,which includes the improvement of phase detector and loop filter,to improve the tracking performance and carrier wave acquisition speed of Costas loop.The simulation results of MATLAB and FPGA verify the effectiveness and reliability of improved digital Costas loop.(2)The traditional Gardner timing synchronization system is studied deeply,and it focuses on conducting detailed analysis on Farrow filter structure in Gardner loop.On this basis,a kind of timing synchronization method based on high order interpolation filter is put forward based on the Farrow filter structure.Simulation performance analysis is also conducted for it through MATLAB,and FPGA is used to realize the timing synchronization system of high order interpolator based on Farrow structure.The simulation results ofMATLAB and FPGA show that the timing synchronization system of high order interpolator based on Farrow structure can realize the timing synchronization function with higher accuracy.(3)The xc6slx45t-type FPGA microchip of Xilinx is used to conduct the hardware implementation for the above methods.The Chipscope through Xilinx tests the three modulation mode of BPSK,QPSK and 8PSK and the three symbol rates of 8MHz,4MHz and2 MHz respectively.The experiment results show that the methods,mentioned above,have good carrier wave synchronization and timing synchronization performance.The research on the carrier wave synchronization and timing synchronization method of digital communication in the paper has achieved a certain result.