TWI864045B - A balise for a railway track - Google Patents

Abstract

A balise such as a Eurobalise for a railway track having planar dielectric circuit substrate design with a rectangular receiver loop antenna and a rectangular transmitter loop antenna formed on said circuit substrate, wherein an input flux to the receiver loop antenna is conform with a predetermined input flux in a balise active reference area and an output field from the transmitter loop antenna is conform with a field from a predetermined current encircling said balise active reference area, and wherein the receiver loop antenna and the transmitter loop antenna having a separation of at least two times a thickness of the dielectric substrate.

Description

Above ground sensors for railway tracks

Invention Field

The invention relates to a ground sensor, which is an electronic ground sensor located between rails, usually as part of an automatic train protection system. In particular, the invention relates to a ground sensor in the European Railway Traffic Management System, ERTMS, the so-called Eurobalise. This ground sensor forms an integral part of the European train control system and is specified for its function and design in a European standard called "FFFIS for Eurobalise". A Eurobalise should comply with the standardization document "SUBSET-036: Specification for Eurobalises".

Invention background

Ground sensors are arranged along the railway tracks to send information from the trackside to passing trains which enable the traffic safety control on the railway tracks by using this information by an automatic monitoring system on board the trains (railway vehicles) moving on the railway tracks. Such an automatic monitoring system is defined as an ATP (Automatic Train Protection) system which can be operated, for example, according to the European standard ERTMS. The link between the ground sensor and an ATP antenna on the train is based on magnetic coupling, which means that the ground sensor and the ATP antenna constitute an air transformer when the antenna is located above or near the ground sensor. The link is bidirectional, the downlink transmitting power from the transmitter on the rail vehicle to the aboveground sensor by magnetic induction of the receiver loop antenna of the aboveground sensor, and the uplink transmitting data to the ATP system onboard the rail vehicle by using the transmitter loop antenna through the aboveground sensor transmitter, the aboveground sensor transmitter being powered by the power received by the receiver loop.

The FFFIS for European standard ground sensors specifies the strength and characteristics of the electromagnetic fields generated by the European standard ground sensors and on-board antennas in the train by first defining two reference loops of predetermined sizes. Therefore, the European standard ground sensors are required to have an effective reference area of 358mm×488mm for a standard size European ground sensor; and an effective reference area of 200mm×390mm for a reduced size European ground sensor. The standard stipulates that the fields generated by the European standard ground sensor and on-board antenna should be consistent with the fields generated by one of the reference loops. This means that the physical size of the European ground sensor must be largely equivalent to the reference loops defined by the standard. In a known European terrestrial sensor, a receiver loop antenna and a transmitter loop antenna are arranged substantially coaxially on the bottom and top, respectively, of a printed circuit board. The loops are substantially arranged superimposed so that two loop antennas meet the size requirements.

The nature of the transmission link is that the two ground sensor loop antennas should be close to each other, as they both interact with the same antenna function on the train. However, the closer they are placed to each other, the more capacitive and inductive coupling will occur between them. This has the effect of re-tuning the transmitter and receiver circuits away from the desired resonant frequencies, and the links become less efficient. Therefore, European standard ground sensors have used thicker than standard circuit boards. In order to alleviate the coupling and re-tuning problems, the above-mentioned known European ground sensors use a circuit board that is approximately 3.2 mm thick, that is, approximately twice the thickness of today's standard thickness circuit boards. A large loop separation is achieved in the known design, which means that there is less coupling between the receiver loop antenna and the transmitter loop antenna. However, this thickness makes the circuit board bulky and expensive.

Summary of invention

In general, the present invention provides a ground sensor in which a receiver ring antenna and a transmitter ring antenna performance conform to a ground sensor effective reference area relative to a predetermined nominal size. In addition, the ground sensor should allow its integration into an ATP system, thereby complying with the requirements generally defined in a relevant standardization document. The standard European standard Ground Sensor Transmission System, SUB-036, Issue 3.1.0, is incorporated into the present invention for reference.

In particular, the aboveground sensor of the present invention will be fixedly mounted between rails of a railway track to wirelessly transmit data to at least one vehicle antenna of a railway vehicle on the railway track, wherein the aboveground sensor comprises: a substantially planar dielectric circuit substrate having a first side facing upward and a second side facing downward when the aboveground sensor is fixedly mounted between two rails, wherein the circuit substrate has a substantially flat substrate thickness; A substantially rectangular receiver loop antenna is formed on the circuit substrate and has a receiver loop central trace along which a receiver loop physical length is defined, wherein an input flux to the receiver loop antenna corresponds to a predetermined input flux in an above-ground sensor effective reference area, and wherein the receiver loop antenna is configured to wirelessly receive operating signals from a vehicle transmitter in a rail vehicle when the rail vehicle is in the vicinity of the above-ground sensor. energy; a receiver circuit connected to the receiver loop antenna by a receiver feed connection and configured to receive the operating energy from the receiver loop antenna; a substantially rectangular transmitter loop antenna formed on the circuit substrate and having a transmitter loop central trace along which a transmitter loop physical length is defined, wherein an output field from the transmitter loop antenna conforms to a field from a predetermined current surrounding the above-ground sensor effective reference area, and and wherein the transmitter ring antenna is configured to wirelessly transmit data to a vehicle receiver in a railway vehicle when the railway vehicle is in the vicinity of the ground sensor; the transmitter circuit is connected to the transmitter ring antenna by a transmitter feed connection and is configured to feed a transmission signal including the data to the transmitter ring antenna; the receiver ring center trace and the transmitter ring center trace have an average separation interval of at least twice the thickness of the substrate.

The loop separation so achieved improves material efficiency and achieves weight reduction by using a relatively thin circuit substrate (circuit board) material. One tenth of an inch (2.5 mm) or preferably one sixteenth of an inch (1.6 mm) will be sufficient. Recent simulations have shown that, contrary to what one might expect, placing the receiver loop antenna inside the transmitter loop antenna in a coplanar manner will have a tolerable effect on the compliance of the antenna performance of the terrestrial sensor, provided it still meets the standardized requirements. Specifically, the simulations show that the field strength compliance requirements according to the European terrestrial sensor specification can be achieved using separate receiver and transmitter loops in the same plane on one side of the circuit substrate. It should be noted that in the case of a coplanar layout, the physical dimensions of at least one of the receiver loop and the transmitter loop, such as the dimension along a centerline, will have to differ significantly from the size of the European standard terrestrial sensor effective reference area stated in the standardization document.

For purposes of the present invention, the concept of the central trace, i.e., an imaginary path essentially in the middle of an antenna loop, is a reasonable approximation of the current path in a loop antenna, although the actual lateral distribution of the currents may deviate slightly from the middle, but generally toward an inner edge of the loop.

When the receiver loop physical length, as defined substantially in free space propagation, is equal to one tenth of a wavelength or more at the operating frequency of the receiver loop antenna, special care must be taken to achieve compliance of an aboveground sensor due to the phenomenon of non-uniform current distribution in the receiver loop antenna. This is the case for standard or reduced size European aboveground sensors. One tenth of a wavelength or more should be understood to define a starting point for a range (in a very narrow band at about 27 MHz for a European aboveground sensor) associated with each operating frequency being considered, with an accuracy of +/- 10%.

An advantageous method of overcoming this undesirable current distribution phenomenon is to provide the receiver loop antenna with two, three, four or more loop segments separated by respective gaps remote from the receiver feed connection, i.e. in addition to the one gap necessary at the feed connection of a loop antenna. Each of the at least one gap is bridged by a respective capacitor to provide a uniform current distribution in the receiver loop antenna. At least in the case of a European standard ground inductor, the capacitor may be a discrete capacitor component which is soldered to adjacent ends of the loop segments forming a conductor pattern printed (etched) on a circuit board. This arrangement of segments and gaps becomes particularly effective if the at least one gap is positioned substantially on a line of symmetry of the receiver ring antenna and/or is positioned substantially equidistantly along the receiver ring antenna.

Several different arrangements of the receiver loop antenna and the transmitter loop antenna can be implemented separately on a printed circuit substrate of the above-ground sensor, each with a set of advantages and possible trade-offs. Both the receiver loop antenna and the transmitter loop antenna can be formed one inside the other on the circuit substrate. This means that an inner edge of one loop is wide enough to encompass an outer edge of the other loop, even if the loops are located on opposite sides of the circuit substrate. It has been found that forming the receiver loop antenna inside the transmitter loop antenna can be advantageous.

For good performance, at least one of the receiver loop antenna and the transmitter loop antenna may be arranged on both sides of the circuit substrate, preferably overlapping each other. An alternative is to provide the receiver loop antenna on only one of the sides of the circuit substrate, if so, it is preferred to provide the receiver loop antenna on the second side as this tends to improve performance gains. In particular, in the latter arrangement, the transmitter loop antenna is preferably arranged on only one of the sides of the circuit substrate, preferably on the first side. The transmitter loop antenna and the receiver loop antenna provided only on opposite sides of the circuit substrate can give a particularly advantageous geometry, wherein both the thickness of the dielectric substrate and the loop spacing in the plane of the dielectric substrate contribute to a relatively large overall loop spacing. To achieve these favorable properties, the substrate thickness is less than or equal to one tenth of an inch.

For the above-ground sensor disclosed herein, a predetermined loop size range can be defined as a difference between the physical length of the receiver loop and the physical length of the transmitter loop of at least 20 mm, preferably 40 mm.

As indicated herein, the above-ground sensor effective reference area is a rectangle of 358 mm by 488 mm or 200 mm by 390 mm, which is substantially concentric and coplanar with the receiver loop antenna and the transmitter loop antenna. Substantially concentric and coplanar should be understood to generally include an approximation, because in some cases the receiver loop antenna and the transmitter loop antenna are not located on the same side of the circuit substrate. With respect to the above-ground sensor effective reference area, a compliance condition for the receiver loop antenna and the transmitter loop antenna is +/- 1.5 dB, respectively.

Although other systematic approaches are contemplated, the above-ground sensor of the present invention is typically one whose receiver ring antenna and its transmitter ring antenna are configured to comply with the European Standard Above-Ground Sensor Transmission System, SUB-SET-036, Issue 3.1.0.

1: Ground sensor

2a: Track

2a: Rail sleeper

3.16: Receiver ring antenna

4: Receiver

5: Energy storage device

6: Resonance circuit

7: Transmitter

8, 18: Transmitter ring antenna

9: Controller

11: Telegraph unit

12: Planning interface

13: Dielectric circuit substrate; circuit substrate; printed circuit substrate

14: First side

15: Second side

17: Receiver power supply connection

19: Transmitter feed connection

21, 22, 23, 24: Ring segments

25, 26, 27: Capacitor

28: Center trace of receiver loop

29: Center trace of transmitter loop

Figure 1 shows how ground sensors are traditionally placed on the sleepers of a railway track.

FIG2 shows a functional block diagram of a ground sensor according to the present invention.

FIG. 3 shows a bottom view of a simplified circuit layout of a ground sensor according to an embodiment of the present invention.

FIG. 4 shows a top view of a simplified circuit layout of a ground sensor according to an embodiment of the present invention.

Figures 5a-5h show cross-sectional views of alternative printed circuit layouts of the ring antenna according to the present invention.

Detailed description of the preferred embodiment

The drawings focus on the circuitry of an above-ground sensor which is typically provided with a weatherproof housing (not shown) having fastening members for fixing the sensor to a railway track. The drawings are not drawn to scale.

FIG. 1 shows a ground sensor 1, in this case a European standard ground sensor, which is arranged in a fixed position between the rails 2a of a railway track. The ground sensor is usually attached to the rail sleeper 2b of the railway track and a group of ground sensors 1 can be formed. One function of the ground sensor 1 is to wirelessly send data to at least one conventional vehicle antenna (not shown) of a railway vehicle (not shown) traveling on the railway track.

FIG. 2 shows in a simplified manner a functional block diagram of a ground sensor 1 of the type to which the present invention relates. The ground sensor 1 has a conductive receiver loop antenna 3, which is configured to receive power from a vehicle transmitter antenna (not shown) passing the ground sensor 1 by magnetic induction. The magnetic field generated by the transmitter antenna causes a current to flow in the receiver loop antenna 3. The current is rectified in a receiver 4 and the associated energy is stored in an energy storage 5. The energy is used to power the consumer circuits of the ground sensor, for example, a resonant circuit 6 in a transmitter 7 of the ground sensor. The aboveground sensor further comprises a conductive transmitter loop antenna 8 configured to be fed by the resonant circuit 6 to transmit data from a controller 9 via its vehicle antenna to the railway vehicle when the vehicle passes over the aboveground sensor. The controller 9 (which is not part of the present invention) has a serial link input 10 and an input from a preset telegraph unit 11 having a planning interface 12.

Figures 3 and 4 show a conventional type of a substantially planar dielectric circuit substrate 13, also referred to as a circuit board. When the ground sensor 1 is positioned in a fixed position between the two rails 2b, it has a first side 14 facing upwards and a second side 15 facing downwards. The circuit substrate 13 has a substantially uniform substrate thickness of about 1.6 or 2.5 mm and is generally too thin to provide sufficient spacing for the loop antennas superimposed on each other on opposite sides of the substrate to meet the stringent requirements of standardized ground sensors such as European standard ground sensors. As ground sensors form part of the railway safety system, their design tends to be conservative. However, as noted, one of the newest designs uses overlapping conductive patterns on opposite sides of a very thick circuit board to provide appropriately spaced receiver and transmitter loops, one on each side of the board and of the same predetermined size.

FIGS. 3 and 4 further illustrate a substantially rectangular receiver loop antenna 16 formed on the circuit substrate 13 and having a receiver loop center trace along which the physical length of the receiver loop is defined, wherein an input flux to the receiver loop antenna conforms to a predetermined input flux in an effective reference area of an above-ground sensor, and wherein the receiver loop antenna 16 is configured to wirelessly receive operating energy from a vehicle transmitter of a railway vehicle when the railway vehicle is in the vicinity of the above-ground sensor, and wherein the receiver 4 is connected to the receiver loop antenna 16 by a receiver feed connection 17 and is configured to receive the operating energy from the receiver loop antenna 16. A substantially rectangular transmitter loop antenna 18 is formed on the circuit substrate 13 and has a transmitter loop central trace along which a transmitter loop physical length is defined, wherein an output field from the transmitter loop antenna 18 corresponds to a field from a predetermined current surrounding the effective reference area of the ground sensor, and wherein the transmitter loop antenna 18 is configured to wirelessly transmit data to a vehicle receiver in a railway vehicle when the railway vehicle is in the vicinity of the ground sensor, and the transmitter 7 is connected to the transmitter loop antenna by a transmitter feed connection 19 and is configured to feed a transmission signal including the data to the transmitter loop antenna 18.

The receiver loop antenna and the transmitter loop antenna are spaced to limit coupling therebetween so that the receiver loop center trace has an average spacing of at least twice the thickness of the dielectric substrate from the transmitter loop center trace. In FIGS. 3 and 4, since the receiver loop antenna is disposed inside the transmitter loop antenna but on an opposite side of the transmitter loop antenna, the spacing between loops is substantially greater than twice the thickness of the dielectric substrate. As shown, there is also a separation gap between the two loops in the plane of the circuit substrate.

The European standard ground sensor of FIGS. 3 and 4 is of standard or reduced size. This means that at the operating frequency of the receiver loop antenna, 27.095 MHz, the physical length of the receiver loop, as defined in free space propagation, is substantially one tenth of a wavelength or more. With this relationship between physical length and wavelength, the ground sensor of the present invention provides a means for a uniform current distribution in the form of a capacitor 20 included in the receiver loop antenna 16. This is an advantageous way to overcome the phenomenon of poor current distribution. In the example shown, the loop antenna is arranged with four loop segments 21, 22, 23, 24 separated by respective gaps remote from the receiver feed connection 17. Each gap is bridged by a capacitor 25, 26, 27 to present a uniform current distribution in the receiver loop antenna. For this European standard terrestrial inductor, the capacitors 25, 26, 27 may be discrete capacitor components that are soldered to adjacent ends of the loop segments 21, 22, 23, 24. This arrangement of segments and gaps becomes particularly effective when the at least one gap is positioned substantially on a line of symmetry of the receiver ring antenna and/or is positioned substantially equidistantly along the receiver ring antenna. It should be noted that the feed connections 17 and 19 may or may not overlap.

Figures 5a-5h show several different arrangements of the receiver loop antenna 16 and the transmitter loop antenna 18, respectively, on a printed circuit substrate 13 of the above-ground sensor. This is shown by the portion marked A-A in Figure 4. The views of Figures 5b-5h correspond to the view of Figure 5a, but show different designs of the conductive traces of the loops. It should be noted that there is an aperture in the circuit substrate inside the loop antenna of Figure 4, which provides a relatively narrow substrate portion for Figures 5a-5h, which depict the different loop geometries, each with a set of advantages and possible trade-offs. Both the receiver loop antenna and the transmitter loop antenna can be formed one inside the other on the circuit substrate. This means that an inner edge of one loop is wide enough to encompass an outer edge of the other loop, even if the loops are located on opposite sides of the circuit substrate. It has been found to be advantageous to form the receiver loop antenna inside the transmitter loop antenna. The center traces of the receiver and transmitter loops are indicated by 28 and 29, respectively.

If a loop antenna is formed by conductive patterns on both sides of the dielectric circuit substrate, a conductive via (not shown) penetrating the substrate is typically used in various locations to connect the conductive patterns of the loop antenna on the opposite sides of the substrate. Preferably, this will be the case in Figures 5c, 5d, and 5g.

For the European standard above ground sensor disclosed in Figures 3 and 4, a predetermined loop size range is defined as the difference between the physical length of the receiver loop and the physical length of the transmitter loop. In this example, this range is greater than 40mm, and for a standard size European standard above ground sensor, the total length of the loop is approximately 1692mm and for a reduced size European standard above ground sensor, the total length of the loop is approximately 1180mm.

An effective reference area of the European standard ground sensor is a rectangle of 358mm x 488mm or 200mm x 390mm, which is substantially concentric and coplanar with the receiver ring antenna and the transmitter ring antenna. Substantially concentric and coplanar should be understood to generally include an approximation, because in some cases the receiver ring antenna and the transmitter ring antenna are not located on the same side of the circuit substrate. With respect to the ground sensor effective reference area, a compliance condition for the receiver ring antenna and the transmitter ring antenna is +/- 1.5dB, respectively. The European standard ground sensor of this embodiment has assembled its receiver ring antenna and its transmitter ring antenna into a European standard ground sensor transmission system, SUBSET-036, Issue 3.1.0.

Although the description is mainly for European standard ground sensors, the inventor foresees that the applicability of the ground sensors of the present invention complies with ERTMS/ETCS, Interface ‘G’ Specification, SUBSET-100, Issue 2.0.0 of February 24, 2012.

1: Ground sensor

3: Receiver ring antenna

4: Receiver

5: Energy storage device

6: Resonance circuit

7: Transmitter

8: Transmitter ring antenna

9: Controller

11: Telegraph unit

12: Planning interface

Claims (12)

A ground sensor is to be fixedly mounted between rails of a railway track to wirelessly transmit data to at least one vehicle antenna of a railway vehicle on the railway track, the ground sensor comprising: a substantially planar dielectric circuit substrate having a first side facing upward and a second side facing downward when the ground sensor is fixedly mounted between the two rails, wherein the circuit substrate has a substantially flat substrate thickness; a substantially rectangular receiver loop antenna formed on the circuit substrate and having a receiver loop a central trace defining a receiver loop physical length along the receiver loop central trace, wherein an input flux to the receiver loop antenna corresponds to a predetermined input flux in an effective reference area of an above-ground sensor, and wherein the receiver loop antenna is configured to wirelessly receive operating energy from a vehicle transmitter in the railway vehicle when in the vicinity of the above-ground sensor, a receiver circuit connected to the receiver loop antenna by a receiver feed connection and configured to receive the operating energy from the receiver loop antenna, a substantially rectangular transmitter loop antenna formed on the circuit substrate and having a transmitter loop center trace defining a transmitter loop physical length along the transmitter loop center trace, wherein an output field from the transmitter loop antenna matches a field from a predetermined current surrounding an effective reference area of the above-ground sensor, and wherein the transmitter loop antenna is configured to wirelessly transmit data to a vehicle receiver in the railway vehicle when in the vicinity of the above-ground sensor, transmitter circuitry connected to the transmitter loop antenna by a transmitter feed connection and configured to transmit the packet A transmission signal containing the data is fed to the transmitter loop antenna, characterized in that the receiver loop center trace and the transmitter loop center trace have an average separation distance of at least twice the thickness of the substrate of the dielectric, the receiver loop antenna has two, three, four or more loop segments separated by respective gaps in addition to a gap at the receiver feed connection of the receiver loop antenna, and each of the respective gaps is bridged by a respective capacitor to present a uniform current distribution in the receiver loop antenna. The ground sensor according to claim 1, further comprising: each of the respective gaps is positioned equidistantly along the receiver ring antenna. The above-ground sensor of claim 1, further comprising: the physical length of the receiver loop is substantially one-tenth or more of a wavelength as defined in free space propagation at the operating frequency of the receiver loop antenna. The ground sensor of claim 3 further comprises: the receiver ring antenna and the transmitter ring antenna are formed on the circuit substrate in a manner that one is inside the other, and the receiver ring antenna is formed inside the transmitter ring antenna. The ground sensor of claim 4 further comprises: the receiver ring antenna is formed on both sides of the circuit substrate, preferably so that it can overlap itself. The ground sensor of claim 5 further comprises: the transmitter ring antenna is formed on both sides of the circuit substrate, preferably so that it can overlap itself. The ground sensor of claim 6 further comprises: the receiver ring antenna is arranged on only one of the side surfaces of the circuit substrate, preferably on the second side surface. The ground sensor of claim 7 further comprises: the transmitter ring antenna is arranged on only one of the side surfaces of the circuit substrate, preferably on the first side surface. The ground sensor of claim 8 further comprises: the transmitter ring antenna and the receiver ring antenna are only arranged on opposite sides of the circuit substrate. The ground sensor of claim 9 further comprises: the thickness of the substrate is less than or equal to 2.54 mm (0.1 inch). The above-ground sensor of claim 10 further comprises: a predetermined loop size range is defined as a difference between the physical length of the receiver loop and the physical length of the transmitter loop, which is at least 20 mm, preferably 40 mm. The ground sensor of any one of claim 11 further comprises: the effective reference area of the ground sensor is a rectangle of 358mm x 488mm or 200mm x 390mm, which is basically concentric and coplanar with the receiver ring antenna and the transmitter ring antenna.