| With the develoPment of electrified railway and high-speed railway great progrss has beenmade in the recent two decades in the theory, system and unit techniques of track circuit whichnow has stepped into a mature application period. Nowadays, no electrified or high-speed railwayscan work without the support of track circuit. With the soaring development of DSP chips andcomputers, it is possible for us to apply advance techniques in the transmission, reception,processing and transmission of the cab signals. In this thesis, we try to use two advanced signalprocessing methods in improving the performance of the cab signal system.This thesis is composed of two parts, first is the wavelet theory and its application in the cabsignal denoising, the second is the modem spectral estimation method and its application in thedecoding of the upper and lower side frequencies of the FSK signals.In part I, we presnt the signal processing history starting from the Fourier transform up towavelet transform. Wavelet analysis is a newly developed technique and has been adopted inmany fields such as image processing and image compression. In chapter I, we study the classicFourier transform and short-time Fourier analysis. The short-time Fourier transform is a modifiedFourier transform which is designed to bring time-information into the Fourier transform. Theirstrongpoint and shortomings are given too. In chapter 2, wavelet analysis, including the wavelettransform is presented. In chapter 3, multiresolution analysis is given. Multiresolution is notoriginated from wavlet analysis, it can give us ways to cnstruct orthogonal compact supportwavelet basis. Chapter 4 discusses the wavelet packets theory, which is the further development ofthe wavelet transform. It can give richer resolution than wavelet theory alone. And in the lastchapter of part I, chapter 5, we utilize the wavelet packets theory to denoise the cab signai.In the second part, moden spectral estimation methods are presnted with concentration onthe AR methods for its simpleness and easiness of carrying out. This part consists of three chapters.In chapter 6, traditional spectral estimation method is introduced and the reasons why we wiIladopt the modem spectral estimation are given, that is, the shortcomings of them. There are a lotof modern spectral estimation techniques, but only the one whose transfer function is rationaltransfer function modeling methods is studied in chapter 7. And in the last chapter of the thesis,some simulation resultS of using Burs algorithm in the cab FSK signal processing fOr recOgnizingthe upper and lower side frequencies of the FSK Signals are given.AcknowledgementI am indebted to many people for their contributions and heIp in the development of researchprocess and this thesis, and would like tO acknowledge them here.I am grateful to my suPervisot, DL Li-Min, Ji' a researcher of Signaling & CommunicationInstitUte of China Academy of Railway Sciences, for his Iongterm mentoring, assistance andsuPport during my research. Many professional opPOminities became POssible because of hisselfless help.I would like to thank ML nding, the deputy director of the Signal and Automatic Controldivision, fOr his selfish help and the opPOrtUnity to take part in some prOjectS. I would Iike tOM Mr. Xuexiang Jia, the deputy director of the Signal and AutOmatic ContrOl division. he gaveme some field exPeriences on the cab signal systems.I also aPpreciate everyone in the Signal and AutOmatic ContrOl division, from whom Ileamed a 1Ot.ThN shouId gO to my family Their encouragemerit has been a source of inspiration tO mewhen the going go tOugh.I aPOlogize to any contributing person I may have overlooked at this time.YanPeng Sun2000.6... |
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