遥测遥控信号的被动解调技术

发布时间：2018-04-03 03:37

本文选题：卫星测控体制　切入点：被动解调　出处：《电子科技大学》2014年硕士论文

【摘要】：随着时代的发展,卫星测控技术在军用和民用方面,都在发挥越来越大的作用,二次调制技术被广泛用于卫星测控领域。本文主要研究了卫星测控系统中常用的统一载波调制信号的时频特征,参数估计方法与被动解调方法。主要完成了PCM/PM,PCM/FM,PCM/BPSK/PM,PCM/QPSK/PM,DSSS/BPSK五类信号的调制识别、参数估计与解调。对于上述问题本文的主要工作如下:首先研究了统一载波调制信号的调制特性和时频特性,然后再根据其不同的特征,如频域特征、平方谱特征、高阶累积量、正交变换后得到的载波分量和信息分量等、设计了一套识别流程:通过信号平方谱性质识别出DSSS/BPSK信号;通过信号的谱线单一性区分出PCM/PM信号;通过信号的信息分量识别PCM/PM信号,最后通过信息分量的平方谱和四次方谱区分PCM/BPSK/PM和PCM/QPSK/PM信号,并给出仿真结果。仿真表明在信噪比SNR?5的环境下,调制类型正确识别率可以达到90%以上。其次在调制识别得到的信号类型的基础上,可以根据其信号特性,估计出一些关键参数,如码速率、载波频率、副载波频率、调制指数等等。对于统一载波调制信号解调,本文采用了锁相环结构,实现了对主载波的跟踪,并通过对副载波信号支路的数字鉴相实现了对PCM/PM的解调,数字鉴频实现了对PCM/FM的解调;通过锁相环来进行副载波的跟踪,实现了对PCM/BPSK/PM以及PCM/QPSK/PM的解调;通过估计出的伪随机码序列,实现了扩频信号的解扩,从而完成信号解调。仿真结果表明,在信噪比SNR?5的环境下,信号的解调误码率低于110?。
[Abstract]:With the development of the times, satellite TT & C technology is playing a more and more important role in both military and civil fields. Secondary modulation technology is widely used in satellite TT & C field.In this paper, the time-frequency characteristics, parameter estimation methods and passive demodulation methods of unified carrier modulation signals in satellite TT & C systems are studied.We mainly completed the modulation identification, parameter estimation and demodulation of five kinds of PCM / PM / PM / PC / PM / PM / QSSS / BPSK signals of PCM / PM / FM / PCM / PM / PM / PCM / QPSK / PMX / DSSS / BPSK.The main work of this paper is as follows: firstly, the modulation characteristics and time-frequency characteristics of unified carrier modulated signals are studied, and then according to their different characteristics, such as frequency domain characteristics, squared spectrum features, high-order cumulants,The carrier component and information component obtained by orthogonal transform are designed to identify the DSSS/BPSK signal by the character of signal squared spectrum, to distinguish the PCM/PM signal by the single spectral line of the signal, and to recognize the PCM/PM signal by the information component of the signal.Finally, the PCM/BPSK/PM and PCM/QPSK/PM signals are distinguished by the square spectrum of the information component and the quadrilateral spectrum, and the simulation results are given.Simulation results show that the correct recognition rate of modulation type can reach over 90% under the environment of signal-to-noise ratio (SNR?5).Secondly, on the basis of the signal types obtained by modulation recognition, some key parameters, such as code rate, carrier frequency, subcarrier frequency, modulation index and so on, can be estimated according to their signal characteristics.For the demodulation of the unified carrier modulation signal, this paper adopts the phase-locked loop structure, realizes the tracking of the main carrier, and realizes the demodulation of the PCM/PM and the demodulation of the PCM/FM by the digital phase discrimination of the sub-carrier signal branch.The demodulation of PCM/BPSK/PM and PCM/QPSK/PM is realized by using phase-locked loop to track subcarriers, and the despreading of spread spectrum signal is realized by estimating the pseudorandom code sequence, thus the demodulation of the signal is completed.The simulation results show that the bit error rate (BER) of signal demodulation is lower than 110g in the environment of signal-to-noise ratio (SNR?5).
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：V556;TN911.3

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