Patent Description:
Ultra-wideband (UWB) communication technology is a technology that uses a high signal bandwidth, in particular for transmitting digital data over a wide spectrum of frequency bands with very low power. For example, UWB technology may use the frequency spectrum of <NUM> to <NUM> and may feature a high-frequency bandwidth of more than <NUM> and very short pulse signals, potentially capable of supporting high data rates. The UWB technology enables a high data throughput for communication devices and a high precision for the localization of devices. In particular, UWB technology may be used for so-called ranging operations, i.e. for determining the distance between communicating devices. Therefore, UWB technology may be used to advantage in various applications, such as automotive applications.

<CIT> describes an electronic device that may include: an ultra wide band (UWB) communication module; a plurality of antennas; and a processor operatively connected to the UWB communication module. The UWB communication module may be configured to: receive first data of an UWB data frame from an external electronic device by using a first antenna set including at least two antennas among the plurality of antennas to measure a first angle of arrival (AOA); receive second data of the UWB data frame by using a second antenna set including at least two antennas among the plurality of antennas to measure a second AOA, where the second antenna set is configured during a section of the UWB data frame that does not include data; and measure the direction of the external electronic device by using the first AOA and the second AOA.

<CIT> describes an RF structure that includes a PA, a PA ground switch coupled between the PA output and ground, a LNA, and a LNA ground switch coupled between the LNA input and ground. The RF structure includes a plurality of directional antenna structures, each including an antenna, a transmit quarter wavelength circuit coupled between the PA output and the antenna, a receive quarter wavelength circuit coupled between the antenna and the LNA input, and an antenna switch coupled between the antenna and ground. Switch control circuitry controls the PA ground switch, the LNA ground switch, and the plurality of antenna switches during transmit and receive operations to control the flow of RF receive signals from the antennas to the LNA and the flow of RF transmit signals from the PA to the antennas. The transmit and receive quarter wavelength circuits may be traces or be constructed of lumped circuit elements.

The article "<NPL>, investigates the feasibility of AoA estimation with UWB radios in a concurrent scheme.

In accordance with a first aspect of the present disclosure, a communication device is provided, as defined in claim <NUM>.

In one or more embodiments, the first mode of operation corresponds to a sequential angle-of-arrival (AoA) mode of operation and the second mode of operation corresponds to a concurrent AoA mode of operation.

In one or more embodiments, each of the first, second and third path further comprises a pre-matching network.

In one or more embodiments, the controller is configured to change the mode of operation of the UWB communication unit from the first mode to the second mode, of from the second mode to the first mode, after a ranging round has been performed by the UWB communication unit.

In one or more embodiments, the controller is configured to change the mode of operation of the UWB communication unit from the first mode to the second mode, of from the second mode to the first mode, after a data frame has been received by the UWB communication unit.

In one or more embodiments, the controller is configured to change the mode of operation of the UWB communication unit in response to a control signal received from an external control system.

In one or more embodiments, the UWB communication unit further comprises a transmitter coupled to the first antenna.

In accordance with a second aspect of the present disclosure, a method of operating a communication device is conceived, as defined in claim <NUM>.

In one or more embodiments, the controller changes the mode of operation of the UWB communication unit from the first mode to the second mode, of from the second mode to the first mode, after a ranging round has been performed by the UWB communication unit.

In one or more embodiments, the controller changes the mode of operation of the UWB communication unit from the first mode to the second mode, of from the second mode to the first mode, after a data frame has been received by the UWB communication unit.

In accordance with a third aspect of the present disclosure, a computer program is provided, as set out in claim <NUM>, comprising executable instructions which, when executed by a controller of a communication device, as set out above, cause said controller to perform a method of the kind set forth.

As mentioned above, UWB is a technology that uses a high signal bandwidth, in particular for transmitting digital data over a wide spectrum of frequency bands with very low power. For example, UWB technology may use the frequency spectrum of <NUM> to <NUM> and may feature a high-frequency bandwidth of more than <NUM> and very short pulse signals, potentially capable of supporting high data rates. The UWB technology enables a high data throughput for communication devices and a high precision for the localization of devices. In particular, UWB technology may be used for so-called ranging operations, i.e. for determining the distance between communicating devices. Therefore, UWB technology may be used to advantage in various applications, such as automotive applications. For example, smart vehicle access systems may employ UWB technology to enable access to a vehicle or another object, in particular by facilitating ranging operations between an access device (e.g. a key fob or a mobile device) and one or more UWB anchors in the vehicle or other object.

In particular, UWB technology - also referred to as impulse-radio ultra-wideband (IR-UWB) - is a RF communication technology that uses pulses having a short duration for data communication. An important feature of IR-UWB technology is that it can be used for secure and accurate distance measurements between two or more devices. Typical distance measurement methods are the so-called single-sided two-way ranging (SS-TWR) method and the double-sided two-way ranging (DS-TWR) method.

Because UWB technology has an accurate distance measurement capability, it may be used to advantage in access systems in which the position of devices should be determined to enable access to an object. For instance, a vehicle access system may comprise a user's smart device (e.g., key fob) and another smart device (e.g., an anchor embedded in the vehicle). To enable access to the vehicle, the user's smart device must have a predefined range relative to the other smart device. Therefore, UWB transceivers are typically configured to operate in a ranging mode. In another example, UWB technology may be used for accessing a building or a predefined space within a building.

In the ranging mode of operation, frames will typically be exchanged between two devices via at least one antenna on each device, and at least a SS-TWR operation will be carried out (which may also be referred to as a ping-pong operation). In particular, channel impulse responses (CIRs) are estimated on both devices, timestamps will be generated based on the CIRs on both devices, and those timestamps are exchanged. Then, a time of flight (ToF) is calculated based on the timestamps and a range (i.e., a distance) is calculated based on the ToF. Alternatively, a DS-TWR operation may be carried out (which may also be referred to as a ping-pong-ping operation). The angle-of-arrival (AoA) mode of operation is similar to the ranging mode, but it involves at least two antennas on one device. In particular, in the AoA mode of operation, two phase values associated with at least two CIRs are calculated on one device. Then, a phase difference of arrival (PDoA) is calculated based on the two-phase values, and an AoA is calculated based on the PDoA. The AoA mode of operation may facilitate a more accurate determination of the position of an object and may thus complement ranging operations performed in the ranging mode.

<FIG> shows an example of a sequential AoA implementation <NUM>. It is noted that UWB-based two-dimensional AoA implementations are typically based on either concurrent operation of two receivers, wherein each receiver is connected to a separate antenna, or operation of one receiver with sequential switching of two antennas. The former may be referred to as a concurrent AoA implementation, while the latter may be referred to as a sequential AoA implementation. An example of the latter type of implementation is shown in <FIG>. In UWB systems an initiator typically exchanges messages containing data frames with a responder via a radio-frequency (RF) signal. If the responder comprises two receiving antennas, it can determine the two-dimensional AoA from the received RF signal. In the sequential AoA implementation <NUM>, a single receiver <NUM> is sufficient. This receiver <NUM> is alternately coupled to a first antenna <NUM> and a second antenna <NUM> by means of controllable switches, which are included in a control block <NUM>. For example, a control circuit included in the control block may alternately open and close the switches in the paths between the receiver <NUM> and the first antenna <NUM> and between the receiver <NUM> and the second antenna <NUM>. When the respective switch is closed, the receiver <NUM> is coupled to the respective antenna. Furthermore, when the respective switch is open, the receiver <NUM> is not coupled to the respective antenna. Instead, the respective antenna may be coupled to ground through the respective switch. Thus, the receiver <NUM> may periodically be reconnected to a different one of the antennas <NUM>, <NUM>, for example after a predefined number of data frames has been received. Since only a single receiver <NUM> is needed, the power consumption is relatively low. However, an external control block (i.e., a control block which is external to the UWB chip including the receiver <NUM>) is typically used to control the sequential switching between the different antennas <NUM>, <NUM>. This may result in a higher bill of materials (BOM), a higher system complexity and a larger printed circuit board (PCB) size.

<FIG> shows an example of a concurrent AoA implementation <NUM>. In the concurrent AoA implementation <NUM>, two receivers <NUM>, <NUM> are used instead of one. Each of said receivers <NUM>, <NUM> is coupled to a separate antenna <NUM>, <NUM>. Thus, two receivers <NUM>, <NUM> are concurrently operated, and each receiver <NUM>, <NUM> receives data frames through the antenna <NUM>, <NUM> connected to it. This may result in a fully integrated solution in the sense that no external control block with switches is needed. The concurrent AoA implementation may result in a higher accuracy of the measured AoA compared to the sequential AoA implementation, but since two receivers <NUM>, <NUM> are used, the power consumption is higher. This, in turn, may result in a reduced battery life in case the communication device is powered by a battery.

Now discussed are a communication device and a corresponding method of operating a communication device, which facilitate achieving an adequate trade-off between an acceptable power consumption and an acceptable measurement accuracy, in particular when AoA measurements are performed by the communication device.

<FIG> shows an illustrative embodiment of a communication device <NUM>. The communication device <NUM> comprises a UWB communication unit <NUM> and a controller <NUM>. The UWB communication unit <NUM> comprises a first receiver <NUM> and a second receiver <NUM>. The UWB communication unit <NUM> is configured to enable UWB communication with at least one external communication device (not shown). Furthermore, the controller <NUM> is configured to control the UWB communication unit <NUM>. In particular, the controller <NUM> is configured to cause the UWB communication unit <NUM>, for example using a control signal, to operate in a first mode in which the first receiver <NUM> is alternately coupled to a first antenna and a second antenna. It is noted that the first antenna and second antenna, which are not shown, may be external to the communication device <NUM>. For instance, if the communication device <NUM> is implemented as a UWB chip, the antennas are typically not integrated into the chip. Furthermore, the controller <NUM> is configured to cause the UWB communication unit <NUM> to operate in a second mode in which the first receiver <NUM> is coupled to the first antenna and the second receiver <NUM> is coupled to the second antenna. In this way, an adequate trade-off may be achieved between an acceptable power consumption and an acceptable accuracy. In particular, when the UWB communication unit <NUM> operates in the first mode, the power consumption may be decreased, at the cost of a lower accuracy. However, in case a higher accuracy is needed, the UWB communication unit <NUM> may be caused to operate in the second mode, in which the accuracy is higher, at the cost of a higher power consumption. Furthermore, in order to achieve said trade-off, no external control block of the kind shown in <FIG> is needed. Thus, a compact system implementation may be realized.

In one or more embodiments, the first mode of operation corresponds to a sequential AoA mode of operation and the second mode of operation corresponds to a concurrent AoA mode of operation. In this way, the communication device may easily be reconfigured to support different AoA modes of operation, which further facilitates achieving the desired trade-off. In particular, the sequential AoA mode of operation may result in a lower power consumption at the cost of a lower measurement accuracy, while the concurrent AoA mode of operation may result in a higher measurement accuracy at the cost of a higher power consumption. It is noted that the AoA mode of operation may be changed in dependence on the application requirements.

According to the invention, the first receiver is coupled to the first antenna through a first path, the second receiver is coupled to the second antenna through a second path, and the first receiver is coupled to the second antenna through a third path. Furthermore, each of the first, second and third path comprises a matching network and a controllable switch for switching the respective path to ground. In this way, the UWB communication unit may easily be controlled, i.e. caused to operate in the desired mode. More specifically, the respective path may be switched to ground via the switch, and the matching network may transform this ground into a high impedance (Zin = "High-Z") that is seen when looking into this path, thereby effectively disabling said path. It is noted that a high impedance means that no RF current can flow into the path. In particular, the controller is configured to cause the UWB communication unit to operate in the first mode by deactivating the second receiver and by alternately switching the first path and the third path to ground, wherein the first path and third path are switched to ground by closing the controllable switch of the respective paths. Furthermore, the second receiver is deactivated upon or after switching the second path to ground, wherein the second path is switched to ground by closing the controllable switch of said second path. Accordingly, the second receiver may be disabled after the second path has been disabled, or the second receiver and the second path may be disabled simultaneously. Furthermore, the controller is configured to cause the UWB communication unit to operate in the second mode by switching the third path to ground, wherein the third path is switched to ground by closing the controllable switch of said third path. This may result in a practical implementation of the presently disclosed communication device.

In one or more embodiments, each of the first, second and third path further comprises a pre-matching network. The use of a pre-matching network facilitates matching the impedance of the matching networks and switches comprised in said paths to the input impedances of the low-noise amplifiers (LNAs) comprised in the receivers. In one or more embodiments, the controller is configured to change the mode of operation of the UWB communication unit from the first mode to the second mode, of from the second mode to the first mode, after a ranging round has been performed by the UWB communication unit. In this way, an optimal mode of operation may be selected for each ranging round to be performed. Furthermore, in one or more embodiments, the controller is configured to change the mode of operation of the UWB communication unit from the first mode to the second mode, of from the second mode to the first mode, after a data frame has been received by the UWB communication unit. In this way, the mode of operation of the UWB communication unit can be changed frequently, for instance to take into account the accuracy requirements associated with particular data frames exchanged between the UWB communication unit and the external communication device. In a practical implementation, the controller is configured to change the mode of operation of the UWB communication unit in response to a control signal received from an external control system. Furthermore, in one or more embodiments, the UWB communication unit further comprises a transmitter coupled to the first antenna. In this way, the UWB communication unit is also able to transmit messages, in addition to receiving messages.

<FIG> shows an illustrative embodiment of a method <NUM> of operating a communication device. The method <NUM> comprises the following steps. At <NUM>, a UWB communication unit comprised in a communication device enables UWB communication with at least one external communication device, wherein the UWB communication unit comprises a first receiver and a second receiver. Furthermore, at <NUM>, a controller comprised in the communication device controls the UWB communication unit, wherein the controller causes the UWB communication unit to operate in a first mode in which the first receiver is alternately coupled to a first antenna and a second antenna, and in a second mode in which the first receiver is coupled to the first antenna and the second receiver is coupled to the second antenna. In this way, an adequate trade-off may be achieved between an acceptable power consumption and an acceptable accuracy.

<FIG> shows another illustrative embodiment of a communication device <NUM>. The communication device <NUM> may be a UWB chip, which is connected to two antennas <NUM>, <NUM>. The communication device <NUM> includes a first receiver <NUM>, which is coupled to the first antenna <NUM> through a first path. The first path contains a matching network (MN) <NUM>, a switch <NUM> and an optional pre-matching network (PMN) <NUM>. Furthermore, the communication device <NUM> comprises a second receiver <NUM>, which is coupled to the second antenna <NUM> through a second path. The second path contains a matching network <NUM>, a switch <NUM> and an optional pre-matching network <NUM>. Furthermore, the first receiver <NUM> is coupled to the second antenna <NUM> through a third path, which contains a matching network <NUM>, a switch <NUM> and an optional pre-matching network <NUM>. The switches <NUM>, <NUM>, <NUM> of the different paths may be controlled by a controller (not shown) comprised in the communication device <NUM>. By controlling the switches <NUM>, <NUM>, <NUM> in a predefined manner, the controller may cause the communication device <NUM> to operate in different AoA measurement modes. For example, by alternately coupling the first receiver <NUM> to the first antenna <NUM> and to the second antenna <NUM> through the first path and the third path, respectively, the communication device <NUM> may operate in a sequential AoA mode. When the communication device <NUM> operates in this mode, the second receiver <NUM> may be deactivated. Furthermore, by coupling the first receiver <NUM> to the first antenna <NUM> through the first path and the second receiver <NUM> to the second antenna <NUM> through the second path, the communication device <NUM> may operate in a concurrent AoA mode. In that case, the third path may be disabled. It is noted that the paths may be enabled by opening the switches in said paths. Furthermore, the paths may be disabled by closing the switches in said paths, which effectively switches the paths to ground.

Accordingly, the communication device <NUM> may be reconfigured in a flexible manner. It is noted that the communication device <NUM> may for example be implemented as an on-chip RF front-end module. By switching the communication device <NUM> into different modes of operation, both sequential AoA measurements and concurrent AoA measurements can be performed, without the need for an off-chip control block. Furthermore, it is noted that the matching networks <NUM>, <NUM>, <NUM> in the different paths ensure that, depending on the position of the switches <NUM>, <NUM>, <NUM> connected thereto, the impedance Zin seen from an antenna port into an RX chain is <NUM> Ohm in RX mode (when the respective switch is open) or high impedance in TX mode (when the respective switch is closed). The optional pre-matching network <NUM>, <NUM>, <NUM> matches the impedance of the matching network <NUM>, <NUM>, <NUM> and the switch <NUM>, <NUM>, <NUM> to the LNA input impedance. Since there are three paths, there are three input impedances Zin,<NUM>, Zin,<NUM> and Zin,<NUM>.

The switch configuration for supporting the sequential AoA mode of operation is shown in Table <NUM>. It is noted that only the state of the switches of the first path (S1) and third path (S3) are shown in Table <NUM>. For this configuration, the switch of the second path (S2) may be closed, so that the second path is effectively switched to ground, the input impedance Zin,<NUM> is high, and the second receiver may be deactivated. Furthermore, the switch configuration for supporting the concurrent AoA mode is shown in Table <NUM>. It is noted that only the state of the switches of the first path (S1) and second path (S2) are shown in Table <NUM>. For this configuration, the switch of the third path (S3) may be closed, so that the third path is effectively switched to ground and impedance Zin,<NUM> is high. In Table <NUM> and Table <NUM>, the value "<NUM>" indicates that a switch is open, while the value "<NUM>" indicates that a switch is closed.

<FIG> shows an illustrative embodiment of a switching sequence <NUM>. While the switches may be configurated statically for the concurrent AoA mode, they should be configured dynamically for the sequential AoA mode. In other words, the first path and the third path should be enabled alternately, by alternately opening and closing the corresponding switches S1, S2 in a predefined manner. <FIG> shows an example of a switching sequence <NUM> for dynamically configuring the switches <NUM>, <NUM> of the first path and the third path (S1 and S3). Initially, the first antenna (ANT1) is connected to the first receiver (RX1), while the second receiver (RX2) is deactivated, so switch S1 has the value "<NUM>" and switch S3 has the value "<NUM>". After the SYNC field and start of frame (SFD) field have passed, the antennas are switched during the gap, so that the second antenna (ANT2) is connected to the first receiver (RX1). Accordingly, switch S3 has the value "<NUM>" and switch S1 has the value "<NUM>", which activates the path from the second antenna (ANT2) to the first receiver (RX1). The gap during which the switching is performed facilitates the settling of transients' effects, such as impedance load changes. Optionally, the antennas may be switched again in the second gap after the secure training sequence (STS).

<FIG> shows an illustrative embodiment of switching an operating mode <NUM>. In particular, it is shown how a UWB chip implementing the proposed RF front-end enables a compact AoA system where AoA accuracy can be traded with power consumption during operation. Assuming that an initiator performs multiple ranging rounds (RR) with a responder, the responder chip may switch the AoA mode during operation as follows. In a first ranging round (RR1) the chip is configured in a sequential AoA mode, in which it has a lower power consumption at the expense of a slightly lower accuracy. The switching between the different antennas in the sequential AoA mode may be performed as described as above. In a second ranging round (RR2) the chip is configured in a concurrent AoA mode, in which it has a higher accuracy, but also a higher current consumption. Finally, in a third ranging round (RR3) the chip is again configured in the sequential AoA mode. In general, there may be an arbitrary sequence of sequential-to-concurrent and concurrent-to-sequential mode transitions. Furthermore, the mode switching may not only be performed between ranging rounds, but also between data frames. In addition, the mode switching may be triggered by an external signal, for example a signal indicating that higher AoA accuracy is needed. It is noted that the front-end may easily be extended to cover additional RF pins and receiver chains, for example to support on-chip sequential and concurrent three-dimensional AoA measurements. Furthermore, an additional transmitter may be connected to the second antenna.

The systems and methods described herein may at least partially be embodied by a computer program or a plurality of computer programs, which may exist in a variety of forms both active and inactive in a single computer system or across multiple computer systems. For example, they may exist as software program(s) comprised of program instructions in source code, object code, executable code or other formats for performing some of the steps. Any of the above may be embodied on a computer-readable medium, which may include storage devices and signals, in compressed or uncompressed form.

Claim 1:
A communication device (<NUM>), comprising:
- an ultra-wideband, UWB, communication unit (<NUM>) configured to enable UWB communication with at least one external communication device, the UWB communication unit (<NUM>) comprising a first receiver (<NUM>) and a second receiver (<NUM>);
- a controller (<NUM>) configured to control the UWB communication unit (<NUM>);
wherein the controller (<NUM>) is configured to cause the UWB communication unit (<NUM>) to operate in a first mode in which the first receiver (<NUM>) is alternately coupled to an external first antenna and an external second antenna; and
wherein the controller (<NUM>) is configured to cause the UWB communication unit (<NUM>) to operate in a second mode in which the first receiver (<NUM>) is coupled to the first antenna and the second receiver (<NUM>) is coupled to the second antenna;
wherein the first receiver (<NUM>) is coupled to the first antenna through a first path, the second receiver (<NUM>) is coupled to the second antenna through a second path, and the first receiver (<NUM>) is coupled to the second antenna through a third path;
characterized in that each of the first, second and third path comprises a matching network and a controllable switch for switching the respective path to ground;
wherein the controller (<NUM>) is configured to cause the UWB communication unit (<NUM>) to operate in the first mode by deactivating the second receiver (<NUM>) and by alternately switching the first path and the third path to ground,
wherein the first path and third path are switched to ground by closing the controllable switch of the respective paths;
wherein the second receiver (<NUM>) is deactivated upon or after switching the second path to ground, wherein the second path is switched to ground by closing the controllable switch of said second path;
wherein the controller (<NUM>) is configured to cause the UWB communication unit (<NUM>) to operate in the second mode by switching the third path to ground, wherein the third path is switched to ground by closing the controllable switch of said third path.