Study On Frequency Shift Track Circuirs Parameters Testing And Signal Precessing Technology

Track circuit signal can ensure railway transport. Rails are used as transmission line to make train communicate with signal processing equipment. The two rails are not only signal lines of track circuits, but also loop current line of locomotive traction current in electrified railway block. Industrial frequency traction current may interference FSK signal. The electric parameters of track circuit must be measured periodically to make sure whether track circuits and signal equipment run normally and to avoid accident.The content of this theme is as follows: without time, without open, without stopping railway transport, and without interrupting traction current of block tested, meanwhile track circuit parameters in electrical and no electrical blocks is measured of on-line, dynamic and real-time. These parameters include voltage of FSK signal, voltage of industrial and harmonic wave interference, upper frequency, lower frequency, carrier frequency and low frequency 18 messages frequency.In this paper, it is introduced how to resolve some technical problems of track circuits parameters on-line tested in electrical railway.Because frequency-shift signal is a kind of modulation signal, it's waveform is two AC sine signal of alternating i.e. upper frequency and lower frequency which was generated by low frequency modulating middle frequency. In testing upper frequency, lower frequency, and modulating frequency, the method of directly testing upper frequency and lower frequency then calculating carrier frequency is adoptedDuring the process of testing low frequency signal, based on analyzing several kinds of demodulation methods, a technique is given that using phase-locked loop CD4046 to demodulate low frequency message. Then shape and measure the frequency. And then the low frequency was measured by microcontroller by the method of measuring period conveniently...