Reserch And Realization Of Parameter Detecting Methods For Frequency-Shift Tarck Signal Based On DSP

As the train speed and density is great improved, the track circuit can transmit more information to the train signal,the train speeding protection system or the train control system that is necessary. The Ministry of Railway has developed two kinds of frequency-shift track circuits based on the primary 4-information frequency-shift system: 18-information frequency-shift auto-blocking track circuit made in China and UM-71 jointless track circuit made in France, and put them into use on some important lines. But at the mean while, the safety of running train becomes austerer and austerer. To guarantee the safety of running train on these lines, it is necessary to detect the parameters of the track signals precisely and timely.With the train accelerating rapidly in our country, the detecting systems based on the traditional methods are facing serious challenge. On the basis of the former research works, we present the detecting method as follows:For the narrow band characteristic of the track signal we use under-sampling instead of Nyquist sampling to reduce the sampling rate. As to the carrier frequency, the spectrum of the 18-information frequency-shift track signal has two peaks, then the carrier frequency is the average of the two peak frequency, to UM-71 jointless track signal, it has only one peak, then the carrier frequency is the peak frequency. Since the energy of 18-information track signal is concentrated around upper frequency and lower frequency, the frequency of the modulation signal is low, and it must have high resolution, we use ZFFT to detect it. As the energy of UM-71 signal is more concentrated, we use extreme value method to detect the frequency of modulation signal in frequency domain, which can satisfy the frequency resolution.At the last we program the parameter detecting methods for frequency-shift track signal with C language and assembly language base on Code Composer Studio of DSP. Then we realize it on the DSP chip of TMS320F2812. Experiments shows that it can satisfy the demand of real time and precision.