Research On DSSS Signal Fast Acquisition Algorithm Under Near-space High Dynamic Scenarios

Efficient and reliable communication transmission is one of the prerequisites to ensure that the high dynamic near space vehicles give full play to the high mobility,high level of promptness,etc..Error-free real-time signal synchronization plays an essential role in the new generation of high dynamic near space vehicles.The fast acquisition of the signal is the core of synchronization,and its performance directly affects the synchronization capability of the high dynamic receivers.In this paper,we study the fast acquisition algorithm of direct spread pseudo code signal under two typical near-space high dynamic scenarios.The major contributions of this work are summarized as follows:We consider extreme high speed but low acceleration near-space high dynamic scenarios,in which the heavy computational burden of conventional acquisition algorithms caused by the limited correlation peak between received signal and local pseudorandom noise(PRN)code is one of the important challenges.Aiming at this challenge,we propose a Double-Layer Time-Frequency Analysis based Fast Fourier Transform(DL-FFT)signal acquisition algorithm.Specifically,the proposed algorithm utilizes the chip folding strategy to search for the chip offset in the time domain with faster speed and introduces fast Fourier Transform based coherent detection to eliminate the ambiguity of chip phase.Meanwhile,in the frequency domain,the step size in search of the Doppler compensation can adjust dynamically itself to improve the precision of acquisition based on the correlation peak ratio.Finally,the numerical analysis and experimental results indicate that the proposed scheme can effectively reduce the computation cost compared with other peer algorithms.We further investigate variable speed maneuverable near-space targets which induced by Chip Distortion and Doppler Migration.It is indicated that correlation peak between received signal and local pseudorandom noise code will be expanded.This leads to high dimensionality of signal acquisition under high accelerating near-space scenarios.To circumvent this problem,a Particle Swarm Match Fourier Transform based Double Block Zero Padding(PM-DBZP)signal acquisition method is proposed by compensating Chip Effects and Doppler Effects simultaneously.Then the particle swarm optimization is employed to optimize the iteration of fast discrete match Fourier factor.Both simulation and theoretical analysis show that the proposed algorithm can reduce the computational complexity while achieving an acceptable acquisition probability and accuracy.In summary,the validity of the proposed signal acquisition algorithms are verified by simulation results.More specifically,the computational burdens of the algorithms are significantly reduced under the premise of guaranteed acquisition performance,which provide strong support for high efficiency data communication of near-space vehicles.