星地测控链路高精度时频同步关键技术与验证
发布时间：2018-11-15 13:47
【摘要】：建立完备的星地测控网络是各国大力发展航空航天工业的重要原因之一,不论是导航定位系统,或是气象遥感系统,均属于星地测控网络的范畴。凭借出色抗干扰能力,直接序列扩频一直以来都是星地测控链路通信方式的首选。作为完成预定测控功能的前提,实现扩频信号的时频同步非常关键。然而,特殊的通信环境和外部条件给接收信号带来两方面的影响:过长的通信距离与恶劣的信道使得接收信号功率大幅衰减,信噪比极低;卫星的高动态特性使接收信号的多普勒效应加剧。若不对接收信号进行精确的时频同步,整个测控业务将面临失败。为此,论文针对采用直接序列扩频的星地测控链路的时频同步关键技术展开研究,主要包括:一、针对链路5s的捕获时间要求以及最高达±150kHz的多普勒频偏,调研伪码捕获的三种方法,选择基于FFT的伪码快速捕获与多普勒频偏一维搜索相结合,差分相干积分45次提高信噪比。通过对接收信号先频偏预补偿,然后进行一次FFT运算与一次IFFT运算并差分相干积分45次后判决,在4.515s内完成伪码捕获。二、针对伪码相位抖动,根据经典的伪码跟踪环路提出一种5路并行的伪码跟踪环路设计方案。通过给5条支路分别设置不同的伪码偏移,取与接收数据相关运算结果最大的支路作为最佳采样支路,完成伪码相位跟踪,精度可达1/4码片。三、针对多普勒频偏预补偿后的残余频偏,使用对调制数据不敏感Costas环进行相位差的锁定、补偿并计算出频差反馈至多普勒频偏预补偿。完成上述方案设计的Simulink仿真。四、基于软件无线电平台,完成星地测控链路高精度时频同步关键技术验证。以FPGA芯片作为主要器件,Verilog作为编程语言,实现时频同步关键技术板上测试,各模块之间配合良好,能完成既定的功能。论文对特定条件下星地测控链路时频同步关键技术进行探究与验证,研究成果已工程实现并测试,具有实用价值,可为我国星地测控网络建设提供参考与支持。
[Abstract]:It is one of the important reasons for the development of aerospace industry to establish a complete satellite-ground TT & C network. Both navigation and positioning system and meteorological remote sensing system belong to the category of satellite-ground TT & C network. Direct sequence spread spectrum (DSSS) is always the first choice of satellite-ground TT & C link communication mode by virtue of its excellent anti-jamming capability. As a prerequisite to complete the scheduled measurement and control function, the time-frequency synchronization of spread spectrum signals is very important. However, the special communication environment and external conditions have two effects on the received signal: the long communication distance and the bad channel make the received signal power attenuate greatly, and the signal-to-noise ratio is very low; The Doppler effect of the received signal is aggravated by the high dynamic characteristics of the satellite. Without accurate time-frequency synchronization, the whole measurement and control service will fail. Therefore, this paper studies the key technologies of time-frequency synchronization of satellite-ground TT & C link using direct sequence spread spectrum, including: first, aiming at the acquisition time requirement of link 5s and the Doppler frequency offset up to 卤150kHz. This paper investigates three methods of PN code acquisition and selects the combination of fast PN code acquisition based on FFT and Doppler frequency offset one-dimensional search to improve signal-to-noise ratio (SNR) 45 times by differential coherent integration. The pseudo code acquisition is completed in 4.515s by precompensation of the received signal frequency offset, one FFT operation and one IFFT operation, and the differential coherent integration is 45 times later. Secondly, according to the classical pseudo code tracking loop, a 5 parallel pseudo code tracking loop design scheme is proposed for pseudo code phase jitter. By setting different pseudo code offsets to each of the five branches, the best sampling branch is the one with the largest correlation with the received data. The pseudo code phase tracking is completed, and the precision is as high as 1 / 4 code chip. Thirdly, for the residual frequency offset after Doppler frequency offset precompensation, the phase difference locking of Costas loop which is not sensitive to modulation data is used to compensate and calculate the frequency difference feedback to Doppler frequency offset precompensation. Finish the Simulink simulation of the above scheme design. 4. Based on the software radio platform, the key technology of high precision time-frequency synchronization of satellite-ground measurement and control link is verified. With FPGA chip as the main device and Verilog as the programming language, the key technology of time-frequency synchronization can be tested on board. This paper explores and verifies the key technologies of time-frequency synchronization of satellite-ground TT & C links under certain conditions. The research results have been realized and tested in engineering, which is of practical value and can provide reference and support for the construction of satellite-ground TT & C network in China.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：V556;TN914.42
本文编号：2333473
[Abstract]:It is one of the important reasons for the development of aerospace industry to establish a complete satellite-ground TT & C network. Both navigation and positioning system and meteorological remote sensing system belong to the category of satellite-ground TT & C network. Direct sequence spread spectrum (DSSS) is always the first choice of satellite-ground TT & C link communication mode by virtue of its excellent anti-jamming capability. As a prerequisite to complete the scheduled measurement and control function, the time-frequency synchronization of spread spectrum signals is very important. However, the special communication environment and external conditions have two effects on the received signal: the long communication distance and the bad channel make the received signal power attenuate greatly, and the signal-to-noise ratio is very low; The Doppler effect of the received signal is aggravated by the high dynamic characteristics of the satellite. Without accurate time-frequency synchronization, the whole measurement and control service will fail. Therefore, this paper studies the key technologies of time-frequency synchronization of satellite-ground TT & C link using direct sequence spread spectrum, including: first, aiming at the acquisition time requirement of link 5s and the Doppler frequency offset up to 卤150kHz. This paper investigates three methods of PN code acquisition and selects the combination of fast PN code acquisition based on FFT and Doppler frequency offset one-dimensional search to improve signal-to-noise ratio (SNR) 45 times by differential coherent integration. The pseudo code acquisition is completed in 4.515s by precompensation of the received signal frequency offset, one FFT operation and one IFFT operation, and the differential coherent integration is 45 times later. Secondly, according to the classical pseudo code tracking loop, a 5 parallel pseudo code tracking loop design scheme is proposed for pseudo code phase jitter. By setting different pseudo code offsets to each of the five branches, the best sampling branch is the one with the largest correlation with the received data. The pseudo code phase tracking is completed, and the precision is as high as 1 / 4 code chip. Thirdly, for the residual frequency offset after Doppler frequency offset precompensation, the phase difference locking of Costas loop which is not sensitive to modulation data is used to compensate and calculate the frequency difference feedback to Doppler frequency offset precompensation. Finish the Simulink simulation of the above scheme design. 4. Based on the software radio platform, the key technology of high precision time-frequency synchronization of satellite-ground measurement and control link is verified. With FPGA chip as the main device and Verilog as the programming language, the key technology of time-frequency synchronization can be tested on board. This paper explores and verifies the key technologies of time-frequency synchronization of satellite-ground TT & C links under certain conditions. The research results have been realized and tested in engineering, which is of practical value and can provide reference and support for the construction of satellite-ground TT & C network in China.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：V556;TN914.42
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