Reasearch On Method For Measurement To Frequency Parameter Of Frequency-shift Track Signal

This paper systematacially introduces background of the development ofFrequency-shift Track signal and the current research status of detection methods.French UM71Frequency-shift Track signal is the main track signal, not only inChina, but also in the world. So with the French UM71Frequency-shift Track signalas the research object, this paper analyzes the time feature and frequency featurethoroughly, and presents a new method to detect the frequency parameters.In order to detect the upper frequency information and the lower frequencyinformation effectively, this paper utilizes the short-time Fourier transform andbarycenter spectrum correction method. UM71Frequency-shift Track signal is "thesingle-peak" form in frequency domain, the upper frequency and lower frequencyaliases together, and they are difficult to be distinguished. This paper separates themin the time domain. Owing to the restriction of the width of the time window, if settime window in the time domain, the resolution of frequency will become poor. Inorder to solve the problem of the frequency resolution, this paper analyzes theshortcomings of spectrum refining of ZOOM-FFT, introduces barycenter spectrumcorrection technology, with the same sampling frequency and sampling points, theaccuracy of detection is improved greatly.In order to detect the frequency information of modulation signal frequency,according to the character of the UM71Frequency-shift Track signal, without thesynchronous carrier at the receiving end, this paper utilizes the method ofself-coherent demodulation. Frequency-shift Track signal and FSK signal have manysimiliars. In ideal condition, the demodulation method of FSK signal can also beapplied to Frequency-shift Track signal. But because of the particularity of railwaysystem, the synchronization carrier cannot be used for the coherent demodulation. Inthis paper, detection signal multiplies the detection signal which is time-delay, then make it enter the low pass filter. After this dispose, the frequency of modulationsignal information remains exact. Then, the signal is transformed with derivation, itmake the frequency information into amplitude information, then count times ofzero-crossing according to the amplitude informatin. The cycle and the frequency ofmodulation signal can be obtained.