Orbit Shift Frequency Signal Detection Techniques

With the development of the industry ,the requirement of industrial data transmission become stricter, both in the signal transmission and inspection technology, After speedup of the train, the frequency-shift track circuits signal plays more important role in the train's safe running insurance as well as malfunction analysis. How to inspect the signal accurately in real time is a question for discussion.The paper analyzes the frequency-shift track circuits signal in frequency spectrum and in time field, emphasizes its spectrum characteristic.As to the carrier frequency, the spectrum of the 18-information auto-blocking track signal has two peaks, then the carrier frequency is the average of the two peak frequency, to UM-71 jointless signal, it has only one peak then the carrier frequency is the peak frequency. Since the frequency of the modulation signal is low, and it must have high resolution, we use ZFFT to detect it.Wavelet transformation is a new tool, which can be applied to Time-domain analysis and Frequency-domain Analysis simultaneously. The operation procedure of Wavelet transformation is as follows: drawing out the useful signal, restraining noise signal, improving signal-to-noise ratio of the system, signal detection is achieved in the noise background. In this paper, using the characteristic of wave-transform to recognize the abrupt signals, we put forward an idea of wavelet-transform-curve . we also bring forward an iterative algorithm of extracting wavelet-ridge-curve.And use it to extract the instantaneous-frequency of frequency shift signal .Based on the calculated instantaneous frequency, the modulating low frequency can be imputed accordingly, thus provding a new scheme for analyzing and decoding the railway dedicated frequency shift signal and UM71 signal. At last, we compared with ZFFT and wavelet-transform-curve two ways ,also we do the MATLAB simulation.And the result shows that the wavelet-transform-curve are accurate and effective.At last,we give the parameter detecting system based on TMS320VC5402.For the reason that the time are finite,the article only do the theory designs.I will do more effort in the future.