Dsp-based High-precision Frequency Shift Signal Detection Technology Research And Implementation

With the development of railroad, locomotive running speed is increasing year byyear. The passing ability and transportation safety of train during the transmission playan important role on the high efficiency and normal operation of whole rail web.Quickly and accurately testing the signal used to conduct train is critical means toguarantee transportation safety. Therefore, make scientific research on railwayFSK(Frequency Shift Keying) signals, it's important to guarantee track circuit operatewell, transportation safety, improve transportation efficiency, satisfy the requirementof increasing speed.In this paper, the railway FSK signals characteristics were analyzed andintroduced the key technology of D SP and the chip of TMS320LF2407A, and then gavea brief introduction of the system and its function. Presently, in China rail locomotivesignal mainly adopts Frequency-shift Keying. It has many advantages of digitalcommunication, but it also has the property of non-linear modulated that makesrealization of real-time and high resolution very difficult. The development of digitalhandling technique and DSP appliance supplies suitable condition for realization of FSKsignal of real-time and high resolution.The traditional method of testing the whole period FSK signals mainly applysingle chip in the time range, they have the shortage of lower testing precision andlimited real-time, therefore, the testing FSK signals system based on DSP, digitalprocessing technology and FFT(Fast Fourier Transform Algorithm) were introduced inthis paper. The system has the advantage of high integration, good real-time, stronganti-interference ability. It's an effective method to testing the signal of railway circuit.The paper conducted the following researches:1. Based on the TMS320LF2407A DSP to design FSK signal testing system.2. Improve the frequency resolution of FSK signal testing, adopts under-ratesampling technology to calculate and analysis the spectrum. This testingmethod puts forward FFT (Fast Fourier Transform Algorithm) to enhance theprecise of A/D conversion, and improve the real-time.