Design Of Parameter Detecting Instrument For Frequency Shift Track Signal Based On TMS320VC5402

The function of railway is very important in our country's economic development, in order to accelerate the development of our country's economy, the Ministry of Railway has developed two kinds of frequency-shift track circuits: 18-information frequency-shift auto-blocking track circuit and UM-71 jointless track circuit, and put them into use on some important lines. The application of them has advanced the development of railway and economy, 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 properly, precisely and timely. The detecting systems based on the traditional methods are facing serious challenge, with the train accelerates rapidly in our country. 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-rate sampling instead of Nyquist sampling to reduce the sampling rate. 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. At the last we give the parameter detecting instrument based on TMS320VC5402. Experiments shows that it can detect the carrier frequency and the low frequency of modulation signal as expected, the resolution of the carrier frequency is 0.3Hz,the detecting error is within ±0.5Hz, and the resolution of the low modulation frequency is 0.07Hz, the detecting error is within ±0.05Hz.