Digital coding FSK track circuit information demodulation method based on spectrum analysis

Abstract

The invention discloses a digital coding FSK track circuit information demodulation method based on frequency spectrum analysis. The method comprises the steps of preprocessing digital coding FSK track circuit information through a front-end circuit; performing spectrum analysis on the preprocessed digital coding FSK track circuit information based on discrete Fourier transform; demodulating all basic frequency point information, verifying demodulated code element information flow, carrying out frequency spectrum amplitude calculation on effective frame information in the demodulated code element information flow, comparing upper and lower edge frequency amplitudes of corresponding basic frequency points, defining and outputting code element values corresponding to code elements accordingto a track circuit BFSK, and recording the code element values.

Description

technical field [0001] The invention relates to the technical field of railway signal spectrum analysis, in particular to a method for demodulating digitally coded FSK track circuit information based on spectrum analysis. Background technique [0002] Frequency shift keying (FSK) is an earlier modulation method used in information transmission. Its main advantages are: easier to implement, better anti-noise and anti-attenuation performance, and widely used in medium and low-speed data transmission. FSK uses a digital signal to modulate the frequency of the carrier. If a binary modulation signal is used, it is called BFSK. [0003] The digitally coded FSK track circuit is the main communication interface between the trackside equipment and the on-board equipment of the automatic train control system. The track circuit obtains and encodes data from the track logic processor, and then sends the encoded data frame to the rail in BFSK modulation mode. The train automatic control...

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Problems solved by technology

[0005] Since coherent digital demodulation needs to recover the carrier and synchronize the carrier phase, the technical implementation is difficult and the cost is high, so it is not suitable for general engineering implementation

[0006] The non-coherent digital demodulation method has more applications. In the field of urban rail transit, the current domestic subway line track circuit loading information mainly adopts digital coding FSK technology, and the demodulation basically adopts the BFSK non-coherent demodulation method built by analog circuits. The composition of its equipment is relatively complex, and any circuit failure or interference will affect the reception of signals, thereby affecting driving.

At the same time, the current track circuit coding and demodulation can only analyze information on one basic frequency point at the same time point. When the device is initialized, it needs to go through a frequency scanning process first, and the digital coding information demodulation can only be started after the frequency scanning is completed.

When the vehicle passes through the insulation section of the track circuit, the basic frequency jumps. At this time, it is often necessary to re-scan the frequency to continue demodulating the encoded information. This method has certain restrictions on the minimum section length and maximum driving speed. When the driving speed When the height is too high or the length of the fork section is short, it is easy to cause code loss and affect driving

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