A track signal filter circuit

Abstract

The invention discloses a track signal filtering circuit which comprises a low-pass filtering unit and a high-pass filtering unit. Band-pass filtering and trapped wave processing are carried out by a band-pass filtering circuit formed by the low-pass filtering unit and the high-pass filtering unit on voltage signals from an induction coil, and the processed voltage signals are outputted to a processor to receive signal decoding processing. The maximum passing frequency of the low-pass filtering unit is 3125Hz, and the stop-band attenuation is greater than 40dB. The minimum passing frequency of the high-pass filtering unit is 400Hz, and the stop-band attenuation is greater than 40dB. The band-pass filtering circuit formed by the low-pass filtering unit and the high-pass filtering unit has a trapped wave suppressing effect on 50Hz signals and 150Hz signals, wherein the attenuation for the 50Hz signals is greater than 80dB, and the attenuation for the 150Hz signals is greater than 60dB. The track signal filtering circuit disclosed by the invention is simple in structure, not only can filter signals outside the bandwidth, but also can suppress interferences of power supply network single-frequency signals substantially.

Description

technical field The invention relates to a filter circuit, in particular to a track signal band-pass filter circuit applied to a track traffic signal system. Background technique The track circuit is used for train occupancy detection and provides continuous operation permission information, and various track information is transmitted in the form of track signals. The train senses the rail current through the induction coil and converts it into a voltage signal. After processing the signal, it obtains the color light signal, speed level signal, etc. required for train operation, and assists the train control system to control the operation of the train. The track signal is a FSK (Frequency Shift Keying, Frequency Shift Keying) modulation waveform, which is synthesized and output by switching two sine waves of different frequencies according to a certain frequency. Different FSK modulation frequencies, that is, the switching frequencies of the two carrier frequencies repres...

AI Technical Summary

Problems solved by technology

However, the disadvantage of this method is that the stopband attenuation of the designed filter circuit will not be greater than 20dB, and it does not have the notch function for the two frequency points of 50Hz and 150Hz, and cannot suppress the influence of the single-frequency signal of the power supply network on the track signal

Images