A Research On Signal Generation And Processing In High Speed Data Transfer System

This paper has its origin in improvement for the communication capacity of equipment.The task adopts the n/4-DQPSK modulation and demodulation technology,which possesses features of high spectrum utilization ratio,better spectrum specification,strong anti-jamming ability,good security and difference demodulation.First,this paper detail discussed the methods and basic theory of this communication system.The modulation and demodulation techniques ofπ/4-DQPSK are mainly studied in this paper and a communication systematic scheme is given.This paper design and realization of each module,such as coding and decoding of the cyclic code,π/4-DQPSK modulation and demodulation,pulse shaping filter,spread spectrum,carrier modulation of IF,DDC,carrier synchronization and Gardner bit synchronization.In regard to burst communication system,a technique for burst synchronous is introduced in detail in the paper.Firstly,IF is transformed to zero by DDC.Then,the initial phase of the processed is acquired(ΔF can be treated as phase estimation if it is too small verses to signal rate),which can make it in the range of fast acquisition band.At last,π/4-DQPSK is transformed to DQPSK and PLL is used to capture the phase.The design of parameters and method of PLL is discussed thoroughly in this paper.