Research And Implementation Of Key Technologies On Satellite Signal Spectrum Monitoring System

With the continuous development of communication technologies,the proportion of satellite communications used in the military field and people's life is becoming more and more large.Monitoring the satellite signal helps to comprehend the current satellite communications quality,and to ensure the satellite communication runs normally.At present,using a spectrum analyzer to monitor the satellite signal manually is the main way,so that real-time monitoring can not be achieved.Aiming at the problem of satellite signal monitoring at present,this paper designs,studies and realizes a multi-carrier satellite signal spectrum monitoring system composed of satellite signal receiver,signal processing center,satellite signal monitoring station and the database,which can realize real-time monitoring of multi-channel signals.The system can estimate the parameters of the satellite signal blind by monitoring the spectrum of satellite signal,including carrier power,signal bandwidth,center frequency estimation,symbol rate estimation and modulation scheme identification.At the same time,interference can be detected and alarmed.In this paper,the key technologies involved in signal processing center are studied.Key technologies include carrier center frequency estimation,symbol rate estimation and modulation scheme identification.Carrier frequency estimation,this paper studies the center-of-gravity estimation method,instantaneous phase estimation method and the decision feedback loop estimation method,this paper improves the center-of-gravity method.The simulation result shows that the improved method has high accuracy,stabilization,easy to achieve and blind estimation advantages compared with the other two methods.Symbol rate estimation,this paper studies the delay multiplication method,the method based on the cyclical stationary characteristic and the method using a velocity-vector.The simulation result shows that the method using a velocity-vector estimation has high accuracy,stabilization,easy to achieve and blind estimation advantages compared with the other two methods.Modulation scheme identification,firstly the statistical characteristics,amplitude characteristics and spectral characteristics of different modulation signals are analyzed.Secondly,the influences of frequency offset on high-order cumulants and higher power spectrum of signal are analyzed.Thirdly,this paper presents a new method of modulation recognition based on high-order cumulants and high-order square spectrum.At last,the improved high-order cumulant method,the joint feature parameter method and the proposed method based on high-order cumulants and the high-order square spectrum method are simulated,the simulation results show that the new method proposed in this paper can not only achieve blind recognition,but also achieve higher recognition rate than the other two methods when the frequency offset exists.In order to facilitate the theoretical analysis of the algorithm,this paper firstly carries on the Matlab GUI realization to the system.Because the satellite signal monitoring realizes real-time,the system finally selects the GPU with the strong parallel computing power as the platform,using the C language to carry on the software realization.Then this article shows the final software interface.At last,This paper tests the system in three aspects: functional testing,time testing and error input testing,the test results show that the system is in full compliance with its design requirements and performance indicators.