Research On The Baseband Design Of Spread Spectrum Receiver Applied To The School Projectile

The accurate attack of artillery is becoming more and more important in today's and future battlefields,and it is extremely difficult to predict and correct the artillery before firing.A new method of calibrating is proposed for the defects faced by traditional calibration methods.With the data link transmission accomplished by launching system and rear command position inside the missile body,battle field can realize the perception of the impact point of projectile at a long distance,thus realizing the calibration function of artillery in real time and automatically.And have correction function real timely and automatically.In this paper,a new correction method is used as the background,the baseband signal processing design of the receiving system in this communication technology is discussed and studied.Firstly,the basic theory of spread spectrum communication system is introduced.According to its own characteristics,it shows the superiority and necessity in the calibration scheme.Taking DS-SS system as the focus of research,the structure of receiving system and the workflow between components in the subject are described.Then the communication distance of the receiving system is calculated theoretically,which is the precondition of the research.By establishing a systematic diffraction model to analyze the diffraction loss in communication links,the maximum diffraction capability is estimated to ensure the communication quality and reliability.Then,aiming at the characteristics of high dynamic Doppler frequency offset in receiving system,the common carrier and spread spectrum PN code acquisition methods are analyzed and compared.This paper chooses the acquisition algorithm which combines serial search with parallel acquisition,and reduces the acquisition time by adding appropriate hardware resources.On this basis,an improved optimization algorithm is proposed.Then,aiming at the difficulty of tracking high dynamic input ramp-up frequency by second-order frequency-locked loop,a method of fine tracking of frequency change by dual-loop switching is proposed,and the synchronization of pseudo-code by delay code loop is completed.Using the simulation tool of Matlab to verify the feasibility of the overall capture and tracking scheme and analyze the performance improvement of the algorithm.After that,based on the overall software architecture,the spread spectrum pseudo-code synchronization module and carrier synchronization module in the correlator system are designed using the top-down modularization idea.Verilog Hardware Description Language is used to implement each module.At the same time,the hardware simulation results are generated with Modlesim tool.Finally,the baseband signal processing algorithm of the ground receiver of the calibration communication system is tested on the hardware of the FPGA.The test results show that the performance of the whole receiver fully meets the system requirements.