关键词: 轨道电路, Zoom-FFT, 过零检测

Abstract: This article introduces the basic principles and signal characteristics of ZPW-2000 track circuits for national railway signal systems in China, the signal transmission paths and working environment of the track circuits, and the significance to safety of analyzing track circuit signals. An effective method for analyzing such signals is introduced, which is used to calculate instantaneous frequency deviation through time-domain zero-crossing detection. Information on the carrier frequency of the track circuits is determined according to the instantaneous frequency deviation and the given information on the carrier frequency. At the same time, low frequency information is obtained regarding only the upper and lower limits of the frequency deviation of the track circuits, and then low frequency information is obtained through the frequency domain Zoom-FFT. This method can not only meet the requirements for low-cost CPU performance, but also perform decoding in a stable way in the case of signal amplitude changes caused by locomotive or traction currents

Key words: track circuit, Zoom-FFT, zero-crossing detection