| Spread spectrum communication,as a communication technology developed rapidly in recent years,is widely used in military communication and civil communication because of its good anti-interference performance,high security and high precision ranging.In this paper,the acquisition and synchronization of the spread spectrum signal,which is the key technology in the spread spectrum measurement and control,is studied and applied to a domestic missile transponder.Due to the transponder signal processing module of limited resources,after the software simulation and analysis of acquisition performance and resource utilization in the traditional matched filter acquisition method,the digital differential filter acquisition method is raised up.Through simulation and analysis,this method can save nearly half of the hardware logic resources and power consumption without any influence on the acquisition performance,and is worthy of use in the spread spectrum measurement and control system.Due to the high Doppler frequency offset between the ground signal and the missile transponder,it is very difficult to use the common PLL to track the carrier wave.This paper presents a cross product automatic carrier frequency tracking algorithm and FLL auxiliary PLL combination tracking method,software simulation and hardware testing on it.Then the carrier assisted technology of the code ring is used to improve the tracking precision,and the concrete design plan is given.After the measurement and analysis,the loop can track the signal accurately when the carrier to noise ratio is 27dB ยท Hz.Finally,the spread spectrum signal acquisition and synchronization design is realized by using FPGA on the missile transponder,and the actual measurement results are given:system acquisition time is 1.8s,the mean of real pseudorange is 5802.5ns,the standard deviation is 0.19ns,the variance is about 0.0361ns2.The system is of high measurement accuracy and meet the technical requirements. |
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