Ds Signal Fast Synchronization Technology Research

As a new type of communications system, spread spectrum communication has many unique advantages, and has been widely used in both military and civilian fields. The synchronization of spread spectrum signal, including acquisition and tracking, is the key problem of spread spectrum communication. The performance of synchronizing has direct impact on the whole spread spectrum communication system.In high dynamic environment, acquisition of spread-spectrum signal, because of the impact of Doppler frequency, is a process of two-dimensional search for PN code phase and Doppler frequency. It will undoubtedly increase the difficulty of acquisition and protract the time of acquisition. This paper presents a rapid DSSS signal acquisition scheme based on Doppler frequency compensating and frequency domain matching. The main idea of this scheme is to filter M PN code cycles of spread spectrum signal using a group of Doppler filter banks, and do phase compensation to the outputs of every Doppler channel. Then the results of FFT are dealt with large selection to gain estimated PN code phase and Doppler frequency based on time correlation between each compensation channel output and local PN code. This scheme achieves the aim of finishing searching PN code phase and Doppler frequency simultaneously after reading in M PN code cycles of spread spectrum signal, which shortens the acquisition time greatly. The simulation results show the feasibility, the high probability of detection and the short acquisition time of this new scheme, which meet the requirements of rapid acquisition in high Dynamic environment. In addition, the design and simulation of this new scheme in Quartus II using FPGA technology is presented in this paper, which shows that the scheme can be used in practical engineering.In this paper, a non-coherent delay-locked loop with a leading-lagging structure is used to achieve the spread-spectrum code tracking. Considering the impact of code Doppler frequency in high dynamic environment, the technology of carrier auxiliary code tracking loop is used in this paper to track high dynamic spread spectrum signal in narrow loop bandwidth. This loop can suppress noise and improve tracking precision. Matlab simulations are carried out after making a detailed analysis on this tracking loop. This paper analysis the effect of loop bandwidth and damping coefficient on the performance of the loop based on the simulation results, which shows that this loop has strong dynamic stress and high tracking precision.