Patent Description:
There are on-going efforts to provide for train traffic to pass borders between countries or regions having different train protection systems. To this end, <CIT> discloses a communication balise aiming to provide operability according to both Eurobalise system specification and KER/KVB system specification. Combining such fundamentally different specifications in a single balise means that it must have two different operational modes. In the different systems, the signals exchanges with the passing train are different. This is a common situation: Non-modulated signals or signals having toggling modulation from the train in the Eurobalise case, which requires Frequency Shift Keying (FSK) response signal from the balise. Signals having non-toggling modulation from the train in the KER/KVB case, which requires Amplitude Shift Keying (ASK) response signal from the balise. Considering the aspiration in <CIT> to provide such a balise having shared components in a common housing, there is a further need for balise circuitry that could allow this.

To meet the further need in the prior art, the invention provides a balise suitable to be arranged fixedly between rails of a railway track to wirelessly communicate with a vehicle communication device of a railway vehicle on the railway track, the balise comprising: a receiver having a receiver loop and being configured to receive from the vehicle communication device via the receiver loop a receive signal having first receive signal characteristics or second receive signal characteristics different to said first receive signal characteristics; the receiver having energy storage circuitry configured to tap energy from the receive signal for powering the balise and having a detector configured provide an indication of whether the receive signal has the first receive signal characteristics or the second receive signal characteristics; a transmitter having a transmitter loop and being configured to transmit to the vehicle communication device via the transmitter loop a first telegram signal in a Frequency Shift Keying (FSK) operational mode according to the Eurobalise specification or a second telegram signal in a Amplitude Shift Keying (ASK) operational mode according to the KER/KVB specification; the transmitter having a variable capacitance, which forms a resonant circuit together with the transmitter loop, an active feedback circuitry having an input and an output both coupled to the resonant circuit, and a switch to selectively short-circuit the input of the active feedback circuitry to render the active feedback circuitry inactive; a controller configured to cause variation of the variable capacitance of the transmitter to attain the FSK operational mode and to cause the switch to short-circuit the input of the active feedback circuitry to attain the ASK operational mode. In the balise, the switch may have a solid-state switch component to short-circuit the input of the active feedback circuitry. Preferably, this component comprises a field effect transistor. These solutions provide the advantage of fast switching in combination with a low impedance. The short-circuiting typically means connecting to signal ground.

In the active feedback circuitry of the balise, there may be included a limiter configured to limit and stabilize oscillation amplitudes in the resonant circuit, preferably in combination the active feedback circuitry having at its input a capacitance in series between the resonant circuit and the switch. These features contribute to providing the advantage of keeping a transmission signal of the first telegram within specification in the FSK operational mode. Specifically, the short-circuiting of the input of the active feedback circuitry coupled to the resonant circuit via the (serial) capacitance CL ensures for the resonant circuit a high impedance load with a high Q value, which is essential for keeping a transmission signal of the first telegram within specification in the ASK operational mode.

In the balise, the controller preferably attains the FSK operational mode in response to the detector providing the indication that the receive signal has the first receive signal characteristics of no modulation of the receive signal, as detected by the detector, whereas the same controller preferably attains the ASK operation mode in response to the detector provides the indication that the receive signal has the second receive signal characteristics of non-toggling modulation of the receive signal, as detected by the detector.

Further, in the balise, the receive signal detectably having toggling modulation preferably implies that the receive signal has the first receive signal characteristics. Alternatively, this implies that the receive signal has the second receive signal characteristics.

The balise may be operated according to Eurobalise specification in FSK operation mode in case the receive signal has first receive signal characteristics of no modulation or toggling modulation. This means that the balise transmits the first telegram in response to the first receive signal characteristics within a strict specification for Eurobalises by means of the shared circuitry of the inventive balise. In this disclosure, operation according to Eurobalise specification defines at least Eurobalise electric parameters of the receive signals, Eurobalise electrical parameters of the transmit signal, and format of the second telegram. A Eurobalise should comply with the standardization document "<NPL>, is incorporated in this disclosure through this reference.

The balise may be operated according to KER/KVB specification in ASK operation mode in case the receive signal has second receive signal characteristics of non-toggling modulation. This means that the balise transmits the second telegram in response to the second receive signal characteristics within a strict specification for KER/KVB balises by means of the shared circuitry of the inventive balise. In this disclosure, operation according to KER/KVB specification defines at least KER/KVB electric parameters of the receive signals, KER/KVB electrical parameters of the transmit signal, and format of the second telegram. A relevant KER/KVB balise specification is UNISIG SUBSET-<NUM>, which could be retrieved from the European Railway Agency.

There is further provided an advantageous method of operating a balise to be arranged fixedly between rails of a railway track to communicate wirelessly with a vehicle communication device of a railway vehicle on the railway track. This method comprises: providing a receiver having a receiver loop and receiving in the receiver from the vehicle communication device via the receiver loop a receive signal having first receive signal characteristics or second receive signal characteristics different to said first receive signal characteristics; providing in the receiver a detector providing an indication of whether the receive signal has the first receive signal characteristics or the second receive signal characteristics; providing a transmitter having a transmitter loop and transmitting from the transmitter to the vehicle communication device via the transmitter loop a first telegram signal in a Frequency Shift Keying (FSK) operational mode according to the Eurobalise specification or a second telegram signal in a.

Amplitude Shift Keying (ASK) operational mode according to the KER/KVB specification; providing in the transmitter a variable capacitance, which forms a resonant circuit together with the transmitter loop, an active feedback circuitry having an input and an output both coupled to the resonant circuit, and a switch selectively short-circuiting the input of the active feedback circuitry to render the active feedback circuitry inactive; providing a controller varying the variable capacitance of the transmitter to operate in the FSK operational mode or switching to short-circuit the input of the active feedback circuitry to operate in the ASK operational mode. The method provides the same or similar advantages to use of the inventive balise. Preferably, the method also involves operating the balise according to Eurobalise specification in FSK operation mode in case the receive signal has first receive signal characteristics of no modulation or toggling modulation; operating the balise according to KER balise specification in ASK operational mode in case the receive signal has second receive signal characteristics of non-toggling modulation.

Huge advantages arise by providing a railway infrastructure comprising rails and a plurality of inventive balises fixedly arranged in a corresponding plurality of locations between the rails. This will allow traffic in a single integrated railway infrastructure by vehicles equipped for different Automatic Train Protection, ATP, systems.

The drawings show details of a balise, a method of operating a balise, and a railway infrastructure disclosed herein. Reference numerals in the drawings are all three-digit numerals, wherein the first digit, being <NUM>-<NUM>, indicates to which one of <FIG>, respectively, that a certain numeral pertains. The second and third digits are the same for corresponding items in different figures. Any exception to this convention would be pointed out explicitly below.

<FIG> show a balise <NUM>, <NUM> to be arranged fixedly between rails 102a on sleepers 102b of a railway track to wirelessly communicate with a conventional vehicle communication device (not shown) carried by a railway vehicle on the railway track, at a time when this vehicle passes the balise <NUM>, <NUM>. The balise has a receiver <NUM> having a receiver antenna loop <NUM> and is configured to receive from the vehicle communication device via the receiver loop <NUM> a receive signal having first receive signal characteristics, such as those intended for a Eurobalise, or second receive signal characteristics, such as those intended for KER balise. The second receive signal characteristics are fundamentally different to said first receive signal characteristic. The receiver <NUM> has energy storage circuitry <NUM> configured to tap energy from the receive signal for providing electrical powering in the balise <NUM>, <NUM>. The receiver <NUM> also has a detector <NUM> configured provide an indication of whether the receive signal has the first receive signal characteristics or the second receive signal characteristics. This is to say that the detector <NUM> determines, for instance, whether the passing railway vehicle communicates according to Eurobalise specification or KER balise specification, based on detection of the receive signal.

The balise <NUM>, <NUM> has a transmitter <NUM>, <NUM> having a transmitter antenna loop <NUM> and is configured to transmit to the vehicle communication device via the transmitter loop <NUM> either a first telegram signal in a Frequency Shift Keying, FSK, operational mode or a second telegram signal in a Amplitude Shift Keying, ASK, operational mode. The transmitter <NUM>, <NUM> has a variable capacitance <NUM> (CR), which forms a resonant circuit <NUM>, <NUM>, <NUM> together with the transmitter loop <NUM>, 408a (LR), an active feedback circuitry <NUM>, <NUM>, <NUM>, <NUM>, <NUM> having an input and an output both coupled to the resonant circuit <NUM>, <NUM>, <NUM>, and a switch <NUM> to selectively short-circuit the input 428a of the active feedback circuitry <NUM>, <NUM>, <NUM>, <NUM>, <NUM> to render the active feedback circuitry inactive. The active feedback circuitry <NUM>, <NUM>, <NUM>, <NUM>, <NUM> typically includes a series-connection of a limiter <NUM>, <NUM>, which provides its input 428a, 428c, an amplifier <NUM>, <NUM>, and a feedback network <NUM> providing its output 318a coupled to the resonant circuit <NUM>, <NUM>, <NUM>. A controller <NUM> is provided, which is capable of causing variation of the variable capacitance <NUM> of the transmitter to attain FSK of the first telegram in the FSK operational mode, while the active feedback circuitry <NUM>, <NUM>, <NUM>, <NUM>, <NUM> is activated. Alternatively, the controller <NUM> causes the switch <NUM> to short-circuit the input 428c of the active feedback circuitry <NUM>, <NUM>, <NUM>, <NUM>, <NUM> to attain the ASK operational mode. In ASK operational mode, preferably, an output of the amplifier <NUM>, <NUM> of the active feedback circuitry <NUM>, <NUM>, <NUM>, <NUM>, <NUM> is short-circuited (similarly to the input 428c), by the controller exerting control or simply as a result of the short-circuiting of the input 428c. It should be noted that for performance purposes the inductance 408a (LR) of the resonant circuit <NUM>, <NUM>, <NUM> is preferably made up of the transmitter loop <NUM> and at least one additional inductive component (not shown separately). This component is applied to render the transmitter <NUM>, <NUM> less sensitive to the environment.

The variable capacitance <NUM> is typically only switchably variable between two fixed values for the purposes herein of forming and transmitting the first telegram signal in the FSK operational mode.

The first telegram is typically different from the second telegram and both are stored in a data memory of the balise <NUM>, <NUM>.

In a preferred embodiment, the balise <NUM>, <NUM> has a single receiver loop <NUM> and a single transmitter loop <NUM>, which are both used in the each of the operational modes of the balise. Moreover, these loops <NUM>, <NUM> are constituted by conductive patterns on a printed circuit board together with other electric circuits and components of the inventive balise <NUM>, <NUM>.

The resonant circuit <NUM> further has coupled to it, in a conventional way for KER balises, an ASK trigger circuit <NUM> operated by the controller <NUM> via an ASK data connection <NUM>.

The resonant circuit <NUM> further has coupled to it, in a conventional way for Eurobalises, a FSK initial trigger circuit <NUM> operated by the controller <NUM> via a FSK power on connection <NUM>.

The switch <NUM> has a solid-state switch, preferable a FET, component to short-circuit the input 428c of the active feedback circuitry <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, at the control of the controller <NUM> via connection <NUM>. This is important for selectively "converting" the electronics of the balise to act in ASK operational mode by "deactivating" active feedback.

The active feedback circuitry <NUM>, <NUM>, <NUM>, <NUM>, <NUM> has a limiter <NUM>, <NUM> configured to limit and stabilize oscillation amplitudes in the resonant circuit <NUM>, <NUM>, <NUM>. This is also important for rendering a favourable transmit (telegram) signal behaviour when the controller <NUM> has selected FSK operational mode and, thus, not short-circuiting the active feedback circuitry <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. In ASK operational mode, the short-circuiting of the input 428c essentially decouples the limiter <NUM>, <NUM> from the resonant circuit <NUM>, <NUM>, <NUM> or at least significantly reduces its influence thereon. This result is important for maintaining performance in the ASK operational mode. In further providing suitable characteristics of the input 428a, 428c of the active feedback circuitry <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, its input 428c is provided with a capacitance 428b (CL) in series between the resonant circuit <NUM>, <NUM>, <NUM> and the switch <NUM>. The actual "limiting" in the limiter <NUM>, <NUM> is essentially provided by a pair of diodes <NUM>, <NUM> connected to supply voltage (VDD) and signal ground (GND), respectively, coupled to the switch <NUM> by an impedance <NUM>. The switch <NUM> is configured when short-circuiting the input 428c by coupling the input to signal ground (GND).

Further, the controller <NUM> of the inventive balise <NUM>, <NUM> is located in a logic block <NUM>. The controller <NUM> has a serial link input <NUM> and connections to a sync error bit pattern module <NUM> and to a default telegram module <NUM>, which in turn has a programming interface connection <NUM>. The controller <NUM> typically has includes a processor and associated data memory.

The controller <NUM> attains the FSK operation mode in response to the detector <NUM> providing the indication that the receive signal has the first receive signal characteristics being no-modulation or toggling modulation.

The controller <NUM> attains the ASK operation mode in response to the detector <NUM> provides the indication that the receive signal has the second receive signal characteristics being non-toggling modulation.

Expressed slightly differently in a similar embodiment, the controller <NUM> is configured to attain the FSK operational mode in response to the detector <NUM> providing the indication that the receive signal has the first receive signal characteristics. The receive signal detectably, by the detector <NUM>, having no modulation implies that the receive signal has the first receive signal characteristics. Further, the controller <NUM> is configured to attain the ASK operational mode in response to the detector <NUM> providing the indication that the receive signal has the second receive signal characteristics. The receive signal detectably, by the detector <NUM>, having non-toggling modulation implies that the receive signal has the second receive signal characteristics.

In addition thereto, there are two mutually excluding alternatives in case the receive signal detectably, by the detector <NUM>, has toggling modulation. This either implies that the receive signal has the first receive signal characteristics or it implies that the receive signal has the second receive signal characteristics. Which alternative is preferable may depend on requirements in a specific railway network in which the inventive balises are to be used.

To summarize, the dual mode balise of the disclosed embodiment enables operating the balise <NUM>, <NUM> according to Eurobalise specification in FSK operational mode in case the receive signal has first receive signal characteristics of no modulation or toggling modulation or operating the balise <NUM>, <NUM> according to KER balise specification in ASK operational mode in case the receive signal has second receive signal characteristics of non-toggling modulation. As an alternative embodiment, for both the balise and the method, the balise <NUM>, <NUM> is operated according to KER balise specification in ASK operational mode in case the receive signal has first receive signal characteristics of toggling modulation, and thus not according to Eurobalise specification in FSK operational mode.

Naturally, some circuitry solutions conventionally found in a Eurobalise or a KER balise are present in the inventive balise but will not be described in detail herein.

An embodiment includes a method of operating a balise <NUM>, <NUM> to be arranged fixedly between rails 102a of a railway track to wirelessly communicate with a vehicle communication device of a railway vehicle on the railway track, the method comprising the steps of:.

Claim 1:
A balise (<NUM>, <NUM>) suitable to be arranged fixedly between rails (102a) of a railway track to communicate wirelessly with a vehicle communication device of a railway vehicle on the railway track, the balise (<NUM>, <NUM>) comprising:
a receiver (<NUM>) having a receiver loop (<NUM>) and being configured to receive from the vehicle communication device via the receiver loop (<NUM>) a receive signal having first receive signal characteristics or second receive signal characteristics different to said first receive signal characteristics;
the receiver (<NUM>) having energy storage circuitry (<NUM>) configured to tap energy from the receive signal for powering the balise (<NUM>, <NUM>) and having a detector (<NUM>) configured to provide an indication of whether the receive signal has the first receive signal characteristics or the second receive signal characteristics;
a transmitter (<NUM>, <NUM>) having a transmitter loop (<NUM>) and being configured to transmit to the vehicle communication device via the transmitter loop (<NUM>) a first telegram signal in a Frequency Shift Keying, FSK, operational mode according to the Eurobalise specification, or a second telegram signal in an Amplitude Shift Keying, ASK, operational mode according to the KER/KVB specification; characterized by said balise further comprising:
the transmitter (<NUM>, <NUM>) having a variable capacitance (<NUM>), which forms a resonant circuit (<NUM>, <NUM>, <NUM>) together with the transmitter loop (<NUM>, 408a), an active feedback circuitry (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) having an input and an output both coupled to the resonant circuit (<NUM>, <NUM>, <NUM>), and a switch (<NUM>) to selectively short-circuit the input (428a) of the active feedback circuitry (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) to render the active feedback circuitry inactive;
a controller (<NUM>) configured to cause variation of the variable capacitance (<NUM>) of the transmitter to attain the FSK operational mode and to cause the switch (<NUM>) to short-circuit the input (428a) of the active feedback circuitry (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) to attain the ASK operational mode.