EP0276332A1 - Verfahren und Einrichtung zur Decodierung eines Signalcodes - Google Patents

Verfahren und Einrichtung zur Decodierung eines Signalcodes Download PDF

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Publication number
EP0276332A1
EP0276332A1 EP86870201A EP86870201A EP0276332A1 EP 0276332 A1 EP0276332 A1 EP 0276332A1 EP 86870201 A EP86870201 A EP 86870201A EP 86870201 A EP86870201 A EP 86870201A EP 0276332 A1 EP0276332 A1 EP 0276332A1
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EP
European Patent Office
Prior art keywords
code
bets
lines
representing
frequency
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP86870201A
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English (en)
French (fr)
Inventor
Francis George Grassart
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alstom Belgium SA
Original Assignee
ACEC Transport SA
ACEC SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ACEC Transport SA, ACEC SA filed Critical ACEC Transport SA
Priority to EP86870201A priority Critical patent/EP0276332A1/de
Priority to CA000555487A priority patent/CA1276727C/fr
Publication of EP0276332A1 publication Critical patent/EP0276332A1/de
Priority to US07/388,312 priority patent/US4965757A/en
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B61—RAILWAYS
    • B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
    • B61L3/00—Devices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal
    • B61L3/16—Continuous control along the route
    • B61L3/22—Continuous control along the route using magnetic or electrostatic induction; using electromagnetic radiation
    • B61L3/24—Continuous control along the route using magnetic or electrostatic induction; using electromagnetic radiation employing different frequencies or coded pulse groups, e.g. in combination with track circuits
    • B61L3/243—Continuous control along the route using magnetic or electrostatic induction; using electromagnetic radiation employing different frequencies or coded pulse groups, e.g. in combination with track circuits using alternating current

Definitions

  • the present invention relates to a method and a device for decoding a code signal produced by modulation of a carrier current at a predetermined rate and for recognizing this signal code among several possible signals with a low probability of error.
  • a typical example of a signal code concerned by the invention is the signal produced by a coded track circuit used in a network of railways to signal to the driver of a train the speed limit authorized for the convoy at the place where is the train.
  • the signal code is produced by a carrier current modulated in amplitude at a determined rate. Each modulation rate is associated with a determined speed limit.
  • the modulation rates are for example 75, 96, 120, 147, 180 and 220 pulses per minute with tolerance of plus or minus two pulses per minute on a carrier current having a frequency of 75 ⁇ 3 hertz.
  • code signals which can for example be associated with the following speed limits: 220 pulses per minute: maximum 60 km / h 180 pulses per minute: 80 km / h maximum 147 pulses per minute: 120 km / h maximum 120 pulses per minute: 130 km / h maximum 96 pulses per minute: 140 km / h maximum 75 pulses per minute: automatic triggering.
  • the code signals which circulate in the track circuits are received by an antenna on board the train and transmitted to the cockpit where a decoder decodes them in order to display the authorized speed limit in clear on the control panel.
  • each signal-code must be decoded and recognized by the decoder with a very low probability of error despite the irregularities which the received signal-code may present and despite the inevitable presence of spurious signals.
  • the disturbances which can alter the signal code are divided into four groups according to their origin: change in the modulation rate (discontinuity of the signal code), phase rotation of the carrier current when passing a switch or a section from channel to next, momentary variation of the level of the signal code or momentary phase jump, presence of current flowing in the channel and coming from external sources (traction return currents, circulation current, crosstalk).
  • the apparatuses known for decoding the code signals of the kind described above use analog demodulation and filtration circuits.
  • the precision and stability of decoding ensured by these known devices are variable both according to the operating circumstances and from one device to another, which makes it necessary to periodically carry out maintenance measurements and calibrations of installed equipment.
  • the complexity and hence the size of these devices increases with the performance achieved in terms of the reliability of the decoding.
  • the invention relates to a decoding method and device which overcomes the drawbacks of the prior art.
  • a decoding method comprising the following steps: after sampling at an adequate sampling frequency, the amplitudes of the time samples in successive blocks of samples of determined length are converted into digital values; the digital values are transposed in the frequency domain by means of a fast Fourier transformation so as to produce and store a set of digital data (FFT) representing the frequency lines of the transform; the relationships between the digital data (FFT) representing the measured frequency lines are compared with theoretical memorized reports in order to generate a set of information (M1-Mn) called "bets" whose values represent the differences between the measured lines and theoretical lines for each signal code; in the set of memorized "bets", selection, for each signal code, of the bet which has the greatest value and memorization of these particular "bets" (MS1-MS N ); in the set of stored particular bets data (MS1-MS N ), the one with the greatest value (MSO) is selected and stored; in response to the selected particular bet (MSO), a signal
  • This method is implemented in an exemplary device which, according to a second aspect of the invention, is characterized in that it comprises a sampler for sampling the signal-code and producing a series of temporal samples in successive blocks of determined length; an analog / digital converter for converting the amplitudes of the time samples of each block of samples to digital values; a storage element for storing said digital values; an organized transformation element, under the control of a stored program, to subject the stored digital values to a rapid Fourier transformation and produce a set of digital signals (FFT) representing the frequency lines of the transform; a logical organizational element (8, 9) for comparing, under the direction of a stored program, the digital FFT signals corresponding to each line situated in the range in which the carrier frequency can vary with the digital FFT signals representing the lines corresponding to the harmonics of the modulation frequency in order to produce a set of information representing the position deviations of the measured frequency lines, and organized means for comparing the information representing the position deviations with stored data which represent the theoretical amplitudes of the lines in order to generate
  • FIG. 1 we see a linear block diagram of the device according to the invention.
  • the elements represented symbolize elements which intervene and cooperate to achieve the same function in the decoding process which will be described, but not necessarily separate material elements.
  • certain elements in FIG. 1 represent elements for receiving and / or storing signals or data; these elements may, as is usual in the art, consist of zones or cells of storage reserved on the same support.
  • the device according to the invention is intended for decoding code signals produced by modulation of a carrier current at predetermined distinct rates and for recognizing a signal code among several possible signals.
  • An example of a typical signal-code is shown in Figure 3. It is a signal obtained by amplitude modulation by all or nothing.
  • the decoding method according to the invention is applicable to other forms of modulation (for example, frequency modulation or phase modulation).
  • the analog code signal SC after usual filtering in a filter 1, is received in a sampling device 2 to be sampled at a sampling frequency ECH adequate to satisfy the Nyquist criterion, that is to say a sampling frequency equal to at least twice the highest frequency present in the composite signal.
  • the sampling device is a device known per se.
  • the amplitudes of the time samples are converted into digital values in an analog / digital converter 3.
  • Blocks of digitized time samples of given length are taken and transmitted successively in a time window 4 so as to favor, in each block, the central samples over the marginal samples, this in order to avoid the appearance of spurious signals due to the discontinuity of the signal at the limits of each time block if the latter does not contain an integer number of alternations of the carrier.
  • the length of a block of time samples is for example 2.44 seconds with a shift of 0.2 seconds from one block to another.
  • Figure 3 is shown the shift of three blocks of time samples B1, B2, B3 derived from the exemplary signal code SC.
  • Each temporal sample of a block is multiplied by a coefficient determined by the position of the sample in the block, the multiplication coefficients CPE being advantageously located on a half-sinusoid.
  • the digital values of the digitized samples of each successive block are received in a storage element 5 so as to be then transposed in the frequency domain by a fast Fourier transformation in a manner known per se.
  • the Fourier transformation means is shown diagrammatically at 6. The Fourier transformation makes it possible to determine the amplitude of each harmonic of a frequency in a composite signal from the form of this signal.
  • FIG. 4 shows the spectrum of the transform for a modulation rate of 75 pulses per minute on a carrier frequency of 75 Hz. It will be noted that the harmonics of the modulation frequency correspond to certain lines of the transform around the carrier of 75 hertz, which can evolve in a frequency range going from 72 to 78 hertz.
  • the fast Fourier transformation is carried out automatically in a transformation element 6, known per se, under the direction of a stored program.
  • each block of samples is represented by a set of digital signals which define the amplitudes of frequency lines of the transform. In the following, these digital signals will be called "FFT data".
  • the FFT data are received in a storage cell 7 with a view to then being automatically processed according to the invention in order to check whether the distribution of the lines corresponding to the carrier frequency and to the harmonics of the modulation frequency is close to the theoretical distribution for a given signal-code.
  • the automatic processing of FFT data in accordance with the present invention is carried out in a logical organizational element represented diagrammatically at 8, under the direction of a stored analysis program.
  • the logical organizational element 8 can of course be combined with the transformation element 6 and the analysis program can be integrated with the FFT transformation program in general digital processing software.
  • the process for processing the FFT data is illustrated by the chain flow diagram in FIG. 2.
  • the starting state A represents the storage of all the FFT data in the storage cell. 7 of FIG. 1.
  • the FFT data corresponding to each of the lines of the frequency range of the carrier is multiplied (function 21) by the FFT data representing the lines corresponding to the harmonics for each signal- coded.
  • the FFT data corresponding to each of the seventeen lines is thus multiplied by the data FFT corresponding to harmonics.
  • the processing process has determined a set of information linked to the position deviations of the measured frequency lines, these data being hereinafter called "EFM information".
  • EFM information a set of information linked to the position deviations of the measured frequency lines
  • Each EFM information is multiplied (function 22) by a digital data (less than one) called “spectral shape coefficient” (CFS) which penalizes the EFM information in proportion to the difference between the value of this information and its value theoretical, that is to say in proportion to the difference between the amplitude of each measured line and its theoretical amplitude as it would result from the relation (1) mentioned above.
  • CFS spectral shape coefficient
  • the spectral shape coefficient is determined (function 23), for each measured line, from the stored FFT data (state A) by comparison of this FFT data with the corresponding theoretical stored data deduced from relation (1) and residing in a memory forming part of the logical organizational element 8 of FIG. 1.
  • This information will be called "bets”.
  • Stakes M1-Mn are stored (function 24) in a storage cell 9 (fig. 1).
  • a selector 10 (fig. 1) then selects (function 25), for each signal code, the bet which has the greatest value in the frequency range considered.
  • the output message MSC is delayed until a sufficient number of confirmations is given by the analysis of several blocks of successive time samples.
  • the duration of this delay is determined here by the increment given to the counter 14 corresponding to the identified signal-code.
  • a selector 16 selects (function 29) the second largest value MS ⁇ , and this datum MS ⁇ is stored (function 30) in a storage cell 17
  • a comparator 18 determines (function 30) the ratio between the first largest value MSO and the second value MS ⁇ . The value of this ratio is called “momentary confidence coefficient" CCM. This coefficient is applied to the counter 14 corresponding to the identified signal code and is used to increment this counter.
  • the selected counter 14 is incremented in response to the CCM signal.
  • the counter 14 is thus incremented during the analysis of one or more blocks of successive samples and the signaling message MSC can then be transmitted to the display device 15.
  • the selected counter 14 is demoted during the analysis of a block of samples ulterior.
  • the decoding process according to the invention thus ensures reliable identification of a code signal among several possible code signals.
  • Fig. 5 illustrates for example the reactions of a decoder according to the invention when changing from a code of 96.15 pulses per minute on a carrier at 75 hertz (code 96) to a code of 220.6 pulses per minute (code 220) .
  • the decoding processing was carried out on the odd harmonics of the modulation only, hence supposing a symmetry of the signal-code. If the received signal-code has a significant asymmetry between the activation time to and the activation time T of the carrier, certain values of the duty cycle to / T may cause the cancellation of one of the harmonics used in the determination of the "bet" and the appearance of even harmonics. In the case where the signal code transmitted is likely to have a duty cycle of less than 0.45 or greater than 0.55, it will be useful to also provide for a spectral analysis as described above but based on even harmonics.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
EP86870201A 1986-12-30 1986-12-30 Verfahren und Einrichtung zur Decodierung eines Signalcodes Withdrawn EP0276332A1 (de)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP86870201A EP0276332A1 (de) 1986-12-30 1986-12-30 Verfahren und Einrichtung zur Decodierung eines Signalcodes
CA000555487A CA1276727C (fr) 1986-12-30 1987-12-29 Procece et dispositif pour decoder un signal-code
US07/388,312 US4965757A (en) 1986-12-30 1989-07-31 Process and device for decoding a code signal

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP86870201A EP0276332A1 (de) 1986-12-30 1986-12-30 Verfahren und Einrichtung zur Decodierung eines Signalcodes

Publications (1)

Publication Number Publication Date
EP0276332A1 true EP0276332A1 (de) 1988-08-03

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EP86870201A Withdrawn EP0276332A1 (de) 1986-12-30 1986-12-30 Verfahren und Einrichtung zur Decodierung eines Signalcodes

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US (1) US4965757A (de)
EP (1) EP0276332A1 (de)
CA (1) CA1276727C (de)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5271038A (en) * 1990-09-10 1993-12-14 Hughes Aircraft Company Distortion suppression using thresholding techniques
US5383225A (en) * 1992-12-17 1995-01-17 Motorola, Inc. Synchronizer for TDMA acquisition signal having an unknown frequency
US5790413A (en) * 1993-03-22 1998-08-04 Exxon Chemical Patents Inc. Plant parameter detection by monitoring of power spectral densities
DE4420348C1 (de) * 1994-06-01 1995-09-21 Siemens Ag Verfahren zum Ermitteln von harmonischen Oberschwingungen zu einer Grundschwingung eines elektrischen Signals
US6308148B1 (en) 1996-05-28 2001-10-23 Cisco Technology, Inc. Network flow data export
DE10325746A1 (de) * 2003-03-17 2004-10-21 Infineon Technologies Ag Verfahren zur Ermittlung eines System-Betriebszustandes
JP4344356B2 (ja) * 2003-03-19 2009-10-14 株式会社アドバンテスト 検波装置、方法、プログラム、記録媒体
RU2446072C1 (ru) * 2010-10-20 2012-03-27 Государственное образовательное учреждение высшего профессионального образования Омский государственный университет путей сообщения Генератор сигналов системы частотного диспетчерского контроля
CN112512871B (zh) 2018-08-08 2023-03-14 旭化成株式会社 气囊用多层膜和气囊

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3958781A (en) * 1975-01-29 1976-05-25 Westinghouse Electric Corporation Train vehicle protection apparatus including signal block occupancy determination
EP0082687A2 (de) * 1981-12-22 1983-06-29 Westinghouse Brake And Signal Company Limited Eisenbahnsignalempfänger
DE3148735A1 (de) * 1981-12-09 1986-10-09 Fried. Krupp Gmbh, 4300 Essen Verfahren und vorrichtung zur frequenzanalyse

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US3848115A (en) * 1973-10-19 1974-11-12 Time Date Corp Vibration control system
US4107775A (en) * 1976-03-16 1978-08-15 Novar Electronics Corporation Human body comparison using driving point parameters
FR2530897B1 (fr) * 1982-03-16 1991-10-31 Victor Company Of Japan Procede et systeme pour une compression de donnees par un echantillonnage a frequence variable
JPS5955523A (ja) * 1982-09-24 1984-03-30 Advantest Corp デジタルスペクトルアナライザ用信号発生器
JPS5979852A (ja) * 1982-10-29 1984-05-09 Asahi Chem Ind Co Ltd 微視的破壊検出装置
JPS6071966A (ja) * 1983-09-28 1985-04-23 Advantest Corp デジタルスペクトルアナライザ
US4715000A (en) * 1985-08-06 1987-12-22 General Electric Company Digital phase-locked loop and frequency measuring device
US4701934A (en) * 1985-09-03 1987-10-20 Motorola, Inc. Method of doppler searching in a digital GPS receiver

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3958781A (en) * 1975-01-29 1976-05-25 Westinghouse Electric Corporation Train vehicle protection apparatus including signal block occupancy determination
DE3148735A1 (de) * 1981-12-09 1986-10-09 Fried. Krupp Gmbh, 4300 Essen Verfahren und vorrichtung zur frequenzanalyse
EP0082687A2 (de) * 1981-12-22 1983-06-29 Westinghouse Brake And Signal Company Limited Eisenbahnsignalempfänger

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CA1276727C (fr) 1990-11-20
US4965757A (en) 1990-10-23

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