METHOD FOR THE DETECTION OF CROSSTALK PHENOMENA

Abstract

A method for the detection of a crosstalk phenomenon in the communication between a wayside transmission unit, especially a balise, and an on-board unit including an antenna unit, of a railway vehicle, includes the steps of receiving an excitation signal of the wayside transmission unit by using the antenna unit in a moving state of the railway vehicle and measuring an electric and/or a magnetic field in a near field of the wayside transmission unit by using the antenna unit upon reception of the excitation signal. A near field to far field transformation on the field measured in the measuring step is performed to detect a presence of a crosstalk phenomenon. A corresponding an on-board unit is also provided.

Claims

1-15. (canceled).

16. A method for the detection of a crosstalk phenomenon in the communication between a wayside transmission unit or balise and an on-board unit of a railway vehicle, the on-board unit including an antenna unit, the method comprising the following steps: using the antenna unit to receive an excitation signal of the wayside transmission unit in a moving state of the railway vehicle; using the antenna unit to measure at least one of an electric or magnetic field in a near field of the wayside transmission unit upon reception of the excitation signal; and performing a near field to far field transformation on the field measured in the measuring step to detect a presence of a crosstalk phenomenon.

17. The method according to claim 16, which further comprises providing the on-board unit with at least one probe connected to the antenna unit and, during the measuring step, measuring the near field of the wayside transmission unit in real time by using the at least one probe for at least one predefined interval.

18. The method according to claim 17, which further comprises calculating the at least one predefined interval according to a formula T=(3*L.sub.WTU)/(V.sub.rv,max), wherein: L.sub.WTU is a geometrical length of the wayside transmission unit, and v.sub.rv,max is a maximum speed limit allowed for the railway vehicle.

19. The method according to claim 17, which further comprises measuring the at least one of electric or magnetic field in the near field of the wayside transmission unit throughout the predefined interval in the measuring step.

20. The method according to claim 16, which further comprises evaluating a pattern of a near field to far field transformation curve received as a result of the performing step.

21. The method according to claim 20, which further comprises determining at least one parameter of the near field to far field transformation curve in the evaluating step, and choosing the at least one parameter from a group of parameters including: a beam width of the near field to far field transformation curve, a polarization of the near field to far field transformation curve, a directivity of the near field to far field transformation curve, and a gain of the near field to far field transformation curve.

22. The method according to claim 21, which further comprises performing the evaluating step by carrying out a sub-step of comparing the at least one determined parameter of the near field to far field transformation curve to a corresponding reference parameter of a reference near field to far field transformation curve of a reference wayside transmission unit.

23. The method according to claim 22, which further comprises outputting an indication signal indicating a presence of a crosstalk phenomenon within the communication between the wayside transmission unit and the on-board unit as soon as an absolute value of a difference between the at least one determined parameter of the near field to far field transformation curve and the corresponding reference parameter of the reference near field to far field transformation curve of the reference wayside transmission unit exceeds a predefined value.

24. The method according to claim 17, which further comprises providing the on-board unit with an nxm field-programmable gate array connected to the at least one probe and allowing for a measurement of nxm near field samples within the measuring step.

25. The method according to claim 16, which further comprises, within the performing step, calculating a far field according to an equation: $A\left(k_x,k_y\right)=\frac{1}{n}.Math.{.Math.}_{i=1}^n.Math.{.Math.}_{k=1}^m.Math.E_{i,k}\left(x,y,0\right).Math.e^{-{\mathrm{jk}}_x.Math.x_i}.Math.e^{-{\mathrm{jk}}_y.Math.y_k},$ wherein: A is a vector amplitude of the electric field, k.sub.x is a propagation constant of the electric field along an x-direction, and k.sub.y is a propagation constant of the electric field along a y-direction.

26. An on-board unit of a railway vehicle, the on-board unit OBU comprising: an antenna unit; the on-board unit being adapted to: use said antenna unit to receive an excitation signal of a wayside transmission unit in a moving state of the railway vehicle; use said antenna unit to measure at least one of an electric or magnetic field in a near field of the wayside transmission unit upon reception of the excitation signal; and perform a near field to far field transformation on the field measured in the measuring step to detect a presence of a crosstalk phenomenon.

27. The on-board unit according to claim 26, which further comprises an nxm-field-programmable gate array.

28. . The on-board unit according to claim 27, which further comprises: a probe electrically connected to said nxm-field-programmable gate array; the on-board unit being adapted to measure at least one of an electric or magnetic field in a near field of the wayside transmission unit in a linear dimension by using said nxm-field-programmable gate array and said probe.

29. The on-board unit according to claim 27, which further comprises: at least two probes electrically connected to said nxm-field-programmable gate array; the on-board unit being adapted to measure at least one of an electric or magnetic field in a near field of the wayside transmission unit in a two dimensional array by using said nxm-field-programmable gate array and said at least two probes.

30. The on-board unit according to claim 29, wherein said at least two probes are disposed along a direction perpendicular to a driving direction of the railway vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Features will become apparent to those of ordinary skill in the art by describing in detail exemplary embodiments with reference to the attached drawings in which:

[0034] FIG. 1 illustrates two different crosstalk phenomena,

[0035] FIG. 2 illustrates an embodiment of a method according to the invention,

[0036] FIG. 3 illustrates different NF2FFT curves of different WTUs, balises and/or line side equipments,

[0037] FIG. 4 illustrates the change in polarization in the NF2FFT curve of an electric field of a balise during the predefined contact length interval T,

[0038] FIG. 5 illustrates an On-board unit according to a first embodiment of the invention,

[0039] FIG. 6 illustrates an On-board unit according to a second embodiment of the invention, and

[0040] FIG. 7 illustrates the rectangular scan surface of the On-board unit according to the second embodiment of the invention.

[0041] In FIG. 2, it is illustrated an embodiment of a method according to the invention. In more detail, FIG. 2 shows two scenarios A and B in which the method is carried out.

[0042] In both scenarios A and B shown in FIG. 2, a railway vehicle 300, which in FIG. 2 is indicated via a rectangular frame, moves on rails into a direction x which is indicated via an arrow. The railway vehicle 300 in this embodiment exemplarily is realized as a train and comprises an On-board unit, OBU 250 that has an antenna unit 200 and a probe 201 connected to the antenna unit 200. In this embodiment, the probe 201 is adapted to measure an electric field E in the near field of a WTU/balise 100, which in FIG. 2 is exemplarily realized as an Eurobalise. However, the invention is not limited to balises. In fact, the method according to the invention can be carried out for all kinds of transponders and be used for the detection of crosstalk phenomena in the communication with such transponders. Furthermore, the invention can also be carried out using multiple probes adapted to measure electric and/or magnetic fields.

[0043] In this embodiment, the probe 201 is placed in a near field region of the WTU 100 keeping a margin with respect to the ground the railway vehicle 300 is riding on. In FIG. 2, the margin is denoted H and exemplarily has a value of 10 cm. However, the distance or margin between the ground and a probe 201 can also differ from the aforementioned value, as long as the probe 201 is arranged in the near field region of the WTU/balise 100 when passing it. The method will be carried out when the OBU 250, and especially the probe 201 connected to the antenna unit 200 of the OBU 250, gets into the range of the WTU 100. In this embodiment, in a first step S.sub.1 of the method, the OBU 250 receives an excitation signal of the WTU/balise 100 via the antenna unit 200 in a moving state of the railway vehicle 300. In more detail, the excitation signal is a predefined excitation signal corresponding to a predefined WTU/balise 100. The excitation signal is received via the antenna unit 200 connected to the probe 201 as soon as the probe 201 arrives within a predetermined range of the predefined WTU/balise 100 the OBU 250 whishes to communicate with. The excitation signal is a predefined signal so that it can be distinguished from the excitation signals of other WTUs, balises or line side equipments.

[0044] Upon the reception of the predefined excitation signal, a second step S.sub.2 of measuring an electric field E in a near field of the WTU/balise 100 via the probe 201 connected to the antenna unit 200 is initiated. Expressed in other words, as soon as the OBU 250 receives the excitation signal, the probe 201 is used to measure the electric field E in a near field of the WTU/balise 100. In general, in the near field of the balise 100, the electric field of the same has a closed loop waveguide pattern which in FIG. 2 is illustrated by arrows arranged in a rectangular shape. In other embodiments of the method, besides the electric field E, also a magnetic field H may be measured. Furthermore, it is also possible to carry out embodiments of the invention in which only a magnetic field H is measured in a near field of a WTU. In this embodiment, the near field of the WTU/balise 100 is measured in real time, using the probe 201 for a predefined interval T which is also referred to as a predefined contact length interval T. The predefined contact length interval T is calculated according to the formula T=(3*L.sub.WTU)/(v.sub.rv,max) wherein L.sub.WTU in this embodiment is the geometrical length of the balise 100 and wherein v.sub.rv,max is the maximum speed limit allowed for the railway vehicle 300. However, the aforementioned formula is a project-specific formula. Thus, any other formula can be used to calculate the predefined contact length interval T.

[0045] In FIG. 2, the second step S.sub.2 of measuring in both scenarios A (shown above) and B (shown below) is indicated via the predefined contact length interval T. As can be seen in FIG. 2, after the predefined contact length interval T has passed, the OBU 250 with the antenna unit 200 and the probe 201 has moved forward relative to the position of the WTU/balise 100. In FIG. 2, the new position of the OBU 250, the antenna unit 200 and the probe 201after the predefined contact length interval T has passedis indicated via dashed frames. In the scenario A shown in FIG. 2, the OBU 250 together with the antenna unit 200 and the probe 201 performs the measurement in the second step S.sub.2 of the method while the train is positioned exactly on or above the WTU/balise 100. The electric field measured of the WTU/balise 100 within or during the predefined contact length interval T thus has a closed loop waveguide pattern. Expressed in other words, an electric field E with a closed loop waveguide pattern is measured during the predefined contact length interval T, as the train is directly positioned on the WTU/balise 100 when the measurement is performed.

[0046] In the third step S.sub.3 of the method, a near field to far field transformation, NF2FFT is performed on the electric field measured in the step of measuring S.sub.2 to detect a presence of a crosstalk phenomenon. In the scenario A shown in FIG. 2, the NF2FFT results in an NF2FFT curve with a narrow beam width, wherein the resulting NF2FFT curve is schematically illustrated in FIG. 2. The NF2FFT curve is characteristic for a situation in which a crosstalk phenomenon is not present in the communication between a WTU/balise 100 and an On-board unit 250, and thus characteristic for a situation in which the WTU/balise 100 and its position are detected correctly.

[0047] However, this is not the case in scenario B which is also shown in FIG. 2. In scenario B, the WTU/balise 100 is detected too early and thus falsely due to the presence of a crosstalk phenomenon. Expressed in other words, in scenario B, the excitation signaldue to crosstalkis detected too early, and the WTU/balise 100 is detected before the train and especially before the OBU 250 passes over the WTU/balise 100. Therefore, in the scenario B, the second step S.sub.2 of measuring is performed when the train and the OBU 250 are not positioned exactly on the WTU/balise 100. Due to this shift in position, the electric field measured by the probe 201 during the predefined contact length interval T has not a closed loop waveguide pattern, but an open loop waveguide pattern, as the probe 201 measures the electric field E which is arising due to the loops and line cables in the field. When the NF2FFT is performed on the electric field measured in scenario B in the second step S.sub.2 of the method, the resulting NF2FFT curve has a broader beam width as the one received in scenario A as described hereinbefore.

[0048] In this embodiment, the method further comprises the fourth step S.sub.4 of evaluating a pattern of the near field to far field transformation, NF2FFT curve received as a result in the step of performing S.sub.3. Furthermore, in this embodiment, the fourth step S.sub.4 of evaluating further comprises the sub-step of determining S.sub.4-1 two parameters of the NF2FFT curve, wherein the parameters in this embodiment exemplarily are the beam width of the NF2FFT curve and the polarization of the NF2FFT curve. However, it is also possible to perform an evaluation of the NF2FFT curve using other parameters of the same, as for example the directivity of the NF2FFT curve, the gain of the NF2FFT curve or any other parameter of the NF2FFT curve suitable for an evaluation. Moreover, in this embodiment, the step of evaluating S.sub.4 further comprises the sub-step of comparing S.sub.4-2 the two determined parameters of the NF2FFT curve to a corresponding reference parameter of a reference NF2FFT curve of a reference WTU.

[0049] In the scenarios A and B, the fourth step S.sub.4 of evaluating and the sub-steps of determining S.sub.4-1 the two parameters of the NF2FFT curve and of comparing S.sub.4-2 the determined parameters of the NF2FFT curve to a corresponding reference parameter of a reference NF2FFT curve of a reference WTU are schematically illustrated. In scenario A, the parameters determined correspond to the parameters expected and calculated or deposited, as the NF2FFT curve of the measured electric field corresponds to the reference NF2FFT curve of the reference WTU, which in FIG. 2 is illustrated as a dotted curve. The two NF2FFT curves substantially have the same beam width and substantially the same polarization. Thus, a crosstalk phenomenon is not detected in scenario A.

[0050] In scenario B, the parameters determined do not correspond to the parameters expected and calculated or deposited, as the NF2FFT curve of the measured electric field does not correspond to the reference NF2FFT curve of the reference WTU. In more detail, the NF2FFT curve received as a result in the third step S.sub.3 of performing and the reference NF2FFT curve have different beam widths andat least in some fractions of the predefined contact length interval Ta different polarization which will be described in greater detail with respect to FIGS. 3 and 4 further below. Thus, in scenario B, the presence of a crosstalk phenomenon is detected.

[0051] Expressed once more in other words, the problem of crosstalk as illustrated in FIG. 1 and as described hereinbefore is solved by the use of a probe 201 and by the performance of a near field to far field transformation, NF2FFT. The NF2FFT is used to provide for a proof whether a crosstalk phenomenon is present while reading a WTU/balise 100. The near fields of the line side equipmentse.g. of different balises and WTUs the train passes when driving along the railsare measured in real time using a probe 201 for a particular contact length interval T. The process/method starts as soon as the antenna device 200 of the On-board unit 250 receives an excitation signal from the wayside WTU/balise 100. The contact length interval T is a project dependent parameter, which is defined as follows: T=(3*L.sub.WTU)/(v.sub.rv,max), wherein L.sub.WTU in this embodiment is the length of the balise 100 and wherein v.sub.rv,max is the maximum speed limit allowed.

[0052] The probe 201 is placed in the near field region keeping a margin with respect to the ground. Via the probe 201, the E field, and in other embodiments also the H field in the near field is measured over the contact length interval T when the WTU/balise 100 is activated. As the train moves in a particular direction, the field is measured in intervals.

[0053] The NF2FF transformation curve will yield a pattern which is formed due to the electric (and magnetic) field radiated from the WTU/balise 100. When the train is exactly on the WTU/balise 100, an electric field is measured on the near field of the WTU/balise 100, where the current is forming a closed loop and hence it can be measured a field with a closed loop waveguide pattern. After the NF2FFT has been performed on the field with the closed loop waveguide pattern, the result will have a narrow beam width pattern.

[0054] In scenario B of FIG. 2, a situation is shown in which crosstalk is given and in which the WTU/balise 100 is detected falsely before the railway vehicle 300 has passed over the WTU/balise 100. In such a situation, the probe 201, which functions as a near field scanner, would measure the electric field that is arising due to the loops and line cables. Therefore, the electric field measured in scenario B has an open loop waveguide pattern in the contact length interval T, giving rise to a broader beam width after the NF2FF transformation is performed on the field measured with the probe 201.

[0055] The near field measured with the probe 201 is transformed to the far field to determine parameters which in this embodiment are the beam width and the polarization of the NF2FFT curve. In other embodiments, other parameters may be determined, as e.g. the directivity and/or the gain of the NF2FFT curve. For the NF2FFT, any transformation method can be chosen, for example a Fourier transformation. The evaluation or correlation to determine whether the WTU/balise 100 is present on the line or not can be performed by comparing it to a standard far field limit set for the respective WTU/balise 100 as described hereinbefore. Due to the distinct resonant frequency and dimension over the contact length interval T, the WTU/balise 100 has a contrasting far field in comparison to other equipments (see FIG. 3). Thus, at the end of the contact length interval Twhen the measurement has been carried outit is possible to detect the presence of a WTU/balise 100 accurately from its NF2FFT pattern.

[0056] In FIG. 3, different NF2FFT curves of different WTUs are illustrated. In more detail, FIG. 3 illustrates three different NF2FFT curves , , for electric fields measured of different WTUs, balises and/or line side equipments 100, wherein the gain is plotted against the ordinate of the diagram shown in FIG. 3 and wherein the predefined contact length interval T is plotted against the abscissa of the diagram shown in FIG. 3.

[0057] Expressed in other words, FIG. 3 shows that the electric and magnetic fields measured of different WTUs, balises and line side equipments have different NF2FFT curves when transformed to a far field. Thus, in the step of evaluating of a method that is according to the invention, it is possible to differentiate the presence of e.g. an Eurobalise from the presence of other WTUs, balises or line side equipments in the near field measurement performed during the predefined contact length interval T. In an ideal scenario, the WTU, balise or line side equipment with the smallest geometrical dimension provides for the thinnest beam width in the far field, which in FIG. 3 is the NF2FFT curve denoted . As already mentioned hereinbefore, in the fourth step S.sub.4 of evaluating of the embodiment of the method as illustrated in FIG. 2 and as described hereinbefore, the beam width and the polarization of the NF2FFT curves are compared with a reference NF2FFT curve of a reference WTU. However, in other embodiments, also a correlation function can come to use within the fourth step S.sub.4 of evaluating, allowing for the detection of the presence of for example a particular WTU or balise.

[0058] Furthermore, also the polarity of the NF2FFT curves differs depending on the time of measurement with respect to the predefined contact length interval T, especially when looking onto the joint S-loop-shaped sections of the curves where the polarity alters the most due to the phase change of current distribution of the electric field which can be detected over the predefined contact length interval T as shown in FIG. 4.

[0059] In more detail, FIG. 4 illustrates the change in polarization in the NF2FFT curve of an electric field of a balise during the predefined contact length interval T. In FIG. 4, the arrows indicate the electric field of a balise in the near field, wherein the long sides of the rectangular frame shown in FIG. 4 represent the predefined contact length interval T. The diagram below the rectangular frame shows the amplitude of the polarization components of the NF2FFT curve corresponding to the aforementioned electric field. In more detail, the diagram shows the amplitude of the horizontal polarization components g and the amplitude of the vertical polarization components h of the aforementioned NF2FFT curve over time t in seconds.

[0060] In FIG. 5, it is illustrated an On-board unit 250 according to a first embodiment of the invention. The On-board unit 250 is realized within a railway vehicle 300, which in this embodiment is exemplarily realized as a train. The On-board unit 250 in this embodiment exemplarily comprises an antenna unit 200, a nxm field-programmable gate array, FPGA 220 and a probe 201 which is arranged outside of the railway vehicle 300 but nevertheless on board of the same. The probe 201 is electrically connected to the FPGA 220 which is electrically connected to the antenna unit 200. In this embodiment, the probe 201 is electrically connected to the center of the FPGA 220 adapted to measure electric and magnetic fields in the near field of a WTU in a linear dimension. The On-board unit 250 is adapted to perform the method according to the invention as described hereinbefore.

[0061] In FIG. 6, it is illustrated an On-board unit 250 according to a second embodiment of the invention. In this embodiment, the OBU 250 is arranged within a train head of a train 300 which is moving along a direction which is indicated via an arrow. Also in this second embodiment, the OBU 250 comprises an antenna unit 200 and a FPGA 220 electrically connected to the antenna unit 200. In contrary to the first embodiment, the OBU 250 of the second embodiment comprises a plurality of probes 201 that are electrically connected to the FPGA 220, wherein three probes 201-1, 201-2, 201-3 of the plurality of probes 201 are shown in FIG. 6. Furthermore, for the sake of a better orientation, a coordinate system is shown in FIG. 6. A x-direction of the coordinate system is arranged in parallel to the moving direction of the train 300, wherein a y-direction of the coordinate system is arranged perpendicular to the moving direction of the train 300.

[0062] In this second embodiment, the probes 201 are arranged along a direction that is parallel to the y-direction of the coordinate system. Via the multiple probes, electric and magnetic fields can be measured in a two dimensional array. The measurement via the probes is performed throughout the aforementioned predefined contact length interval T in every /12 interval, wherein corresponds to the wavelength of the balise and can be scanned via the probes 201 of the On-board unit 250. In other embodiments, the measurement via the probes can also be performed throughout any other predefined contact length interval T and in any other interval, for example in every /100, /200 or /300 interval. The aforementioned /X-interval can also be a project specific parameter. In this embodiment, the distance between probes 201 is measured and given as an input parameter for the NF2FFT. Similarly, in this embodiment, the FPGA 220 is adapted to measure the near field in every /X distance, e.g. in every /300 distance. Furthermore, in this embodiment, the scan array has two different scanning widths and is optimized to get the best performance.

[0063] With such an On-board unit 250 comprising multiple probes 201, it is possible to scan a plain rectangular scan surface, wherein in every /12 interval, an electric and/or magnetic field is measured and stored in a matrix as shown in FIG. 7. In FIG. 7, the measurements of the electric and/or magnetic fields J.sub.201-1, J.sub.201-2, J.sub.201-3 performed by the corresponding probes 201-1, 201-2, 201-3 are stored within the columns and rows of the matrix. If nxm near field samples are gathered, the far field can be calculated according to the equation:

[00002]$A\left(k_x,k_y\right)=\frac{1}{n}.Math.{.Math.}_{i=1}^n.Math.{.Math.}_{k=1}^m.Math.E_{i,k}\left(x,y,0\right).Math.e^{-{\mathrm{jk}}_x.Math.x_i}.Math.e^{-{\mathrm{jk}}_y.Math.y_k},$

wherein A is the vector amplitude of the electric field E, k.sub.x is the propagation constant of the electric field E along a x-direction and wherein k.sub.y is the propagation constant of the electric field E along a y-direction. From this equation, all the far field parameters can be determined, as e.g. the directivity, gain, beam width and polarization of the NF2FFT.

[0064] Moreover, for example an Eurobalise has a predefined center frequency and a loop antenna arranged inside which provide for a unique far field pattern with respect to its transducer length. Therefore, the diameter of the loop antenna or the dimensions of other trackside elements have different antenna dimensions and hence different radiation characteristics.

REFERENCE SIGNS

[0065] 100 Wayside transmission unit, WTU, balise

[0066] 170 Inaccurate position

[0067] 200 Antenna unit

[0068] 201, 201-1, 201-2, 201-3 Probe

[0069] 220 Field-programmable gate array, FPGA

[0070] 250 On-board Unit, OBU

[0071] 300 Railway vehicle, train

[0072] h Vertical polarization components

[0073] g Horizontal polarization components

[0074] , , Different NF2FFT curves

[0075] J.sub.201-1, J.sub.201-2, J.sub.201-3 Measurements of the electric and/or magnetic fields

[0076] S.sub.1 Step of receiving

[0077] S.sub.2 Step of measuring

[0078] S.sub.3 Step of performing

[0079] S.sub.4 Step of evaluating

[0080] S.sub.4-1 Sub-step of determining

[0081] S.sub.4-2 Sub-step of comparing