JPH10244942A - Train position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noise canceller circuit superior in the noise proof charac teristic, and to detect a train position, by determining a correlation value of an inverse FFT signal for converting a (J) signal into an original state before the FFT and frequency analyzation, and a PN code used in a transmitting part. SOLUTION: The frequency of a PN code(pseudonoise code) received from a terminal edge side R of a rail T and output from a demodulator circuit 7, is analyzed by FFT by a FFT frequency analyzing part 20b through an A/D converting circuit 20a. Then the same is returned to a specific PN code length through a line spectrum clip part 20c and an inverse FFT part 20d, to be output to a digital correlation unit 22. The correlation value is determined between the PN code used in the transmitting part, and a signal transmitted from a noise canceller circuit 20. When a track circuit T is short-circuited by an axle of a train (a), a signal level from the noise cenceller circuit 20 is lowered, and a specific correlation value can not be obtained, thereby the existence of the train can be detected through a track relay TR.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a train position detecting apparatus employing a spread spectrum communication system.

[0002]

2. Description of the Related Art The present applicant has previously disclosed in Japanese Patent Application Laid-Open No. Hei.
In Japanese Patent Publication No. 32 and the like, a carrier having a predetermined frequency is spread and applied with a predetermined pseudo-noise code (PN code) to a starting end of a rail forming a track circuit, and a signal received from an end of the rail is applied. A train detection device that detects the presence or absence of a train by performing despreading processing with the above-described PN is proposed.

As described above, the train position detecting apparatus employing the spread spectrum communication system (SS communication system) has many features such as improvement of noise resistance and mutual interference with adjacent track circuits. .

The track circuit is in an environment that is susceptible to noise. In other words, the track circuit is not only applied with the train line current for driving the train, and there is power supply harmonic noise, but also when installed together with the existing equipment, narrow-band signals such as AM modulated waves are also generated. Present and high levels of these line spectral noises are received in the spread signal.

When a large line spectrum noise such as the power supply harmonic noise described above is received without taking any measures, the noise resistance is determined by the processing gain.

Therefore, the applicant of the present invention has disclosed in
No. 54437 proposes a train position detecting device including a noise canceller circuit capable of effectively removing the above-mentioned line spectrum noise.

Referring to FIG. 2, the above proposed device will be described. Each track circuit T, T ', T "(FIG. 2 shows only three track circuits to simplify the drawing. Since the train detection devices provided for each of the above-described embodiments have the same configuration, a train position detection device corresponding to the track circuit T will be described below.

[0008] A starting end side S of a track circuit T (hereinafter, sometimes referred to as a rail T) and an end side R are electrically connected to an equipment room b. The receivers a and b are installed so that the position of the train in the block section T can be detected.

[0009] The transmitting section a comprises a signal generator 1, a spreading circuit 2 and a transmitter 3. Signal generator 1 is configured carrier (f _c) of a predetermined frequency to output to spreading circuit 2. The spreading circuit 2 receives a PN code from a PN code generator 4 for generating a predetermined PN code (PN ₁ ).
After diffusion treatment the carrier (f _c) using the code, is configured to output to the next of the transmitter 3. This transmitter 3
Is formed from a well-known amplifier and outputs the rail T
Is supplied to the start end side A of.

The receiving section b comprises a receiver 5, a band-pass filter circuit 6, a demodulation circuit 7, a noise canceller circuit 8, a low-pass filter 9, and a correlation matched filter circuit 10. The receiver 5 is formed by a well-known amplifier circuit, and outputs the output signal to a band-pass filter circuit 6.
It is configured to output to Demodulating circuit 7, the signal generator 1 is configured to divide process using a carrier (f _c) which is sent to the spreading circuit 2.

The noise canceller circuit 8 converts the signal including the PN code (PN ₁ ) from the demodulation circuit 7 into a well-known FFT signal.
(Fast Fourier Transform) Analyzes the frequency within the required band according to the frequency analysis method, and if there is a level difference greater than a predetermined level from the spectrum of the received reference signal wave, it is determined to be noise. Then, the noise component is removed. The operation of the noise canceller circuit 8 is described in Japanese Unexamined Patent Application Publication No. 5-25443.
Since it is described in detail in No. 7, further description is omitted.

The signal from which noise has been removed, output from the noise canceller circuit 8, is supplied to the next low-pass filter circuit 9.
Is input to the matched filter circuit 10. The matched filter circuit 10 is formed from a well-known correlation matched filter circuit, receives a PN code (PN ₁ ) from the PN code generator 4, and receives a P signal from the low-pass filter circuit 9.
It is configured to detect a state of coincidence with the N code (PN ₁ ) and drive the track relay TR based on the presence or absence of the state of coincidence.

[0013]

A train position detecting device having a noise canceller circuit according to the above proposal is capable of detecting noise and S
When there is a large difference from the S signal, the noise component can be effectively removed. However, when the difference is not so large, there is a problem that the effect of removing the noise component cannot be expected so much.

Accordingly, an object of the present invention is to provide a train position detecting device having a noise canceller circuit having more excellent noise resistance characteristics.

[0015]

In order to achieve the above-mentioned object, a train position detecting apparatus according to the present invention is arranged such that a predetermined carrier is spread with a predetermined PN code to form a track circuit at a starting end of a rail. The signal received from the terminal end of the rail is demodulated with the carrier wave to extract a signal including the PN code, and the correlation value of the PN code in the extracted signal is determined to determine the presence or absence of a train. In the train position detecting device for detecting, a FFT frequency analyzing means for performing frequency analysis by FFT of the extracted signal, a clipping means for clipping a signal of a predetermined size or more which has been frequency-analyzed by FFT, Inverse FF for the remaining signal
T, and an inverse FFT means for converting the signal to an original state before frequency analysis by FFT, and a correlation value detecting means for obtaining a correlation value between the inverse FFT signal and the PN code. It is characterized by.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a train position detection device according to one embodiment.

The same components as those of the previously proposed device in FIG. 2 are denoted by the same reference numerals, and the description of these components will be repeated, so that only the new portions will be denoted by different reference numerals.

In the figure, reference numeral 20 denotes a digital noise canceller circuit, which is configured so that an output signal from the demodulation circuit 7 is input via a low-pass filter 21.

The noise canceller circuit 20 comprises an analog-to-digital (A / D) conversion circuit 20a, an FFT frequency analysis unit (FFT analysis unit in FIG. 1) 20b, a line spectrum clipping unit 20c, and an inverse FFT unit 20d. Have been.

In FIG. 1, reference numeral 22 denotes a digital correlator, and reference numeral 23 denotes a drive circuit for driving the orbit relay TR based on the correlation value of the PN code (PN ₁ ) detected by the digital correlator 22.

Next, the train detecting operation of the train detecting apparatus having the above configuration will be described.

The spread signal (SS signal) applied to the starting end S of the rail T, and the processing operation from the receiving end R of the rail T to demodulation by the demodulation circuit 7 are the same as those in FIG. Therefore, it is omitted.

The analog signal including the PN code (PN ₁ ) output from the demodulation circuit 7 is converted into an analog signal by the A / D conversion circuit 20.
After being converted into a digital signal in a, the FFT frequency analysis unit 20b performs FFT and frequency analysis.

FIG. 1A shows an FFT frequency analysis unit 20.
b schematically shows the state of the frequency analysis, where b is the line spectrum of the PN code (PN ₁ ) represented on the time axis, and b is the noise caused by power harmonics, for example. FIG.

The line spectrum clipping section 20c performs the processing of clipping the line spectrum shown in the above item (b). That is, in the line spectrum clipping section 20c, as schematically shown in FIG. 2B, the magnitude of the line spectrum of the PN code (PN ₁ ) shown in FIG. Is set to a predetermined threshold value (A-A), and a process of cutting line spectral components beyond this is performed. FIG. 1C is a schematic diagram showing a state after the cut processing (clip processing).

After the line spectrum clipping section 20c removes most of the line spectrum caused by noise, the line spectrum is returned to the original state before frequency analysis by FFT in the inverse FFT section 20d. , And is output to the next digital correlator 22.

The digital correlator 22 uses the data of the same PN code (PN ₁ ) as the reference data as the PN code (PN ₁ ) used in the transmitting section A as a reference data and correlates the signal transmitted from the noise canceller circuit 20 with the signal. A value is required.

If the track circuit T is not short-circuited on the axle of the train a, the signal P from the noise canceller circuit 20
Since the N code (PN ₁ ) is included, the digital correlator 22 can obtain a predetermined correlation value at this time. Therefore, the track relay TR is lifted (ON) via the drive circuit 23 and can detect that there is no train.

When the track T is short-circuited at the axle of the train a, the signal level from the noise canceller circuit 20 is reduced. At this time, the digital correlator 22 cannot obtain a predetermined correlation value. , The driving circuit 23
Unable to lift (ON) via track relay TR and fall (OF)
F), and the presence of a train can be detected.

[0030]

The train position detecting apparatus according to the present invention performs FFT on a signal containing a received PN code and performs frequency analysis.
FT frequency analyzing means;
Inverse FFT of the remaining clipped signal and FF
Inverse FF that converts to the original state before frequency analysis by T
Since the T means and the correlation value detecting means for obtaining the correlation value between the inverse FFT signal and the PN code can be used, it is possible to effectively remove line spectrum noise caused by power supply harmonics.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a train position detecting device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of the above proposed device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 signal generator 2 spreading circuit 3 transmitter 4 PN code generator 5 receiver 7 demodulation circuit 20 noise canceller circuit 20 a digital-to-analog converter 20 b FFT frequency analysis unit 20 c line spectrum clipping unit 20 d inverse FFT unit 21 low-pass filter 22 digital correlator 23 Drive circuit a Train T, T '. T "track circuit (rail)

Claims (1)

[Claims] 1. A predetermined carrier is spread by a predetermined PN code and applied to the starting end of a rail forming a track circuit, and a signal received from an end of the rail is demodulated by the carrier to form the PN. Extract the signal containing the sign,
In a train position detecting apparatus for detecting the presence or absence of a train by obtaining a correlation value of the PN code in the extracted signal, an FFT for performing frequency analysis on the extracted signal by FFT
Frequency analyzing means, clipping means for clipping a signal of a predetermined size or more which has been frequency-analyzed by FFT, inverse FFT of the remaining clipped signal, and
Inverse FF that converts to the original state before frequency analysis by T
A train position detecting device comprising: T means; and correlation value detecting means for obtaining a correlation value between the signal subjected to inverse FFT and the PN code.