Parameters Detecting Of UM71 Frequency-shift Track Signal And Its Realization Based On DSP

The jointless track circuit is an advanced control system which is used to control the trains. The rail is used as transmission line for transmitting signals in this system, in order to meet the need of transmitting multi-purpose control information. The reliability and quality of the transmitted signals have direct relation to the safety of trains'function. Because of this, it is necessary to detect the parameters of the track signals precisely and timely, in order to inspect whether the track circuit and signal equipments are working well. Finally, the hidden disasters can be avoided, and the safety of the trains'function can be ensured.With the railway's speed raise in our country, the detecting systems based on the traditional methods are facing serious challenge. This paper mainly researched the methods of detecting modulation signal frequency,upper and down side frequencies,carrier frequency and signal voltage of the UM71 jointless track signal.Through analyzing the spectrum of the FSK signal we can know that, in the spectrum of the FSK signal, the distance of the two spectrums nearby is the low modulation signal, therefore the key problem of the low modulation signal detection is how to improve the resolution of frequency detection. In this paper, aiming at the narrow band characteristic of the frequency-shift track signal, we use sub-sampling instead of Nyquist sampling to reduce the sampling rate; Aiming at the cases that the signal's spectrum energy is concentrate and the frequency of the modulation signal is low, we pick-up the part which spectrum energy is concentrate to do a further spectrum detection after the sub-sampling, in order to gained a high resolution of frequency detection. Because of the FSK signal is non-line modulated, the top frequency spectrum isn't the side frequency, this paper firstly through the method of analyzing the FSK signal's phase to pick-up the pure single signal inside the half modulation cycle, and then through the method of Rife to calculate and gained the value of high precision upper and down side frequencies. In order to improve the ability of anti-jamming, this paper also offered a improvement method of Rife. Moreover when testing the voltage of the FSK signal, the rectified signal is directly putted into the A/D channels of DSP to do sampling processing.At the last, we designed a UM71 track signal parameters detecting system base on TMS320F2812, and implemented part functions of the frequency-shift track signal detecting.