Patent Description:
According to a first aspect of the present disclosure there is provided an ultra-wideband, UWB, receiver module, as defined in claim <NUM>.

Synchronizing the UWB receiver module in this way can advantageously account for any (unpredictable) timing offsets between the UWB transmitter module and the UWB receiver module and can also reduce the processing that is required to identify any reflected versions of the subsequent UWB signalling because the CIR does not need to be calculated for all of the channel taps.

In one or more embodiments, the UWB signalling comprises UWB radar signalling.

In one or more embodiments, the processor is configured to identify a predetermined feature in the CIR that corresponds to reception of the UWB signalling via a direct path from the UWB transmitter module.

In one or more embodiments, the processor is configured to identify one or more of the following predetermined features in the CIR:.

In one or more embodiments, the UWB signalling comprises an initial UWB radar signalling frame; and the subsequent UWB signalling comprises one or more subsequent UWB radar signalling frames.

In one or more embodiments, the channel tap that is associated with the predetermined feature in the CIR comprises:.

In one or more embodiments, the UWB signalling comprises UWB ranging signalling and UWB radar signalling, and
the processor is configured to:.

In one or more embodiments, the processor is configured to:
synchronize the UWB receiver module for reception of subsequent UWB radar signalling based on the channel tap that is associated with the identified feature in the CIR, and the estimated frequency or timing offsets.

In one or more embodiments, the processor is configured to process the UWB ranging signalling in order to estimate, and compensate for, carrier frequency offset.

In one or more embodiments, the processor is configured to process the UWB ranging signalling in order to estimate, and compensate for, one or both of:.

There is also provided a multi-device radar system comprising:.

In one or more embodiments, the UWB receiver module and the UWB transmitter module have a shared or a common clock.

According to a further aspect of the present disclosure, there is provided a method of synchronizing an ultra-wideband, UWB, receiver module, as defined in claim <NUM>.

In a multi-device radar system, multiple radar devices are collocated to receive range and velocity information from objects in the environment at different viewing angles. A common problem is to synchronize the multiple devices such that the transmitters (TX) and receivers (RX) of each device are synchronized with the TX and RX of every other device of the radar system, which is needed whenever the radar devices cooperate with one another (multiple-input multiple-output (MIMO, multi-static etc.)). A key aspect of synchronization is whether the devices have a shared clock or independent clocks.

<CIT> describes methods, apparatus and systems for wireless material sensing. In one example, a described system comprises: a transmitter configured for transmitting, using transmit antennas, a first wireless signal through a wireless multipath channel of a venue; a receiver configured for receiving, using receive antennas, a second wireless signal through the wireless multipath channel; and a processor. The second wireless signal comprises a reflection or a refraction of the first wireless signal at a surface of a target material of an object in the venue. The processor is configured for: obtaining a plurality of channel information (CI) of the wireless multipath channel based on the second wireless signal, wherein each CI is associated with a respective transmit antenna and a respective receive antenna; computing a material analytics based on the plurality of CI; and determining a type of the target material of the object based on the material analytics.

<CIT> describes a processing module for a receiver device configured to provide for processing of a frame received by the receiver device from a transmitter device, the at least one frame comprising a plurality of repeating predetermined synchronization symbols for providing synchronization between the processing module and the transmitter device and one or more start-of-frame symbols defining the end of the synchronization symbols, the processing module configured to: perform cross correlation to obtain a cross-correlation function on i) at least a part of the received frame; with ii) a predetermined modulation sequence used to modulate the one or more start-of-frame symbols and not the synchronization symbols; and determine the location of the start-of-frame symbols based on an increase, above a threshold increase, in the cross-correlation function from a negative cross-correlation with the synchronization symbols to a greater cross-correlation with the part of the received frame containing the start-of-frame symbols.

<CIT> describes relatively short turnaround times in conjunction with two-way ranging to, for example, facilitate accurate ranging measurements when the relative clock drift between ranging nodes (e.g., devices) is relatively high. In some aspects, relatively short turnaround times are achieved through the use of a symmetric channel that is defined to enable concurrent transmission of ranging messages between nodes. For example, a symmetric channel may be established by configuring the nodes to receive one or more pulses associated with a received ranging message in between pulse transmissions associated with a transmitted ranging message. In this way, one node may send a ranging timestamp shortly after the other node sends its ranging timestamp, thereby mitigating the impact of the clock drift on the ranging measurements.

<FIG> shows a multi-device radar system, where the two radar devices <NUM> that are shown have a shared clock <NUM>. <FIG> shows a multi-device radar system, where the two radar devices <NUM> that are shown each have their own independent clock <NUM>.

In a radar system based on ultra-wideband (UWB) the TX transmits a series of pulses within a frame, and an RX receives the radar reflections and determines a channel impulse response (CIR) that contains the target movement as changes of amplitude and phase in the CIR taps (or range tap, which are equivalent to distance). The goal of synchronization is to align the CIRs of the multiple RX such that the target responses from the viewing angles are correctly combined. Two ways of performing synchronization are wired synchronization and wireless synchronization.

Wired synchronization has several drawbacks:.

In addition, synchronizing the local oscillator (LO) signals of TX and RX phase-locked loops (PLLs) has additional disadvantages:.

Examples disclosed herein relate to methods and systems for wirelessly synchronizing multiple UWB radar devices, irrespective of whether they share a clock or have independent clocks. UWB signalling can relate to signalling that has a frequency in the range of <NUM> to <NUM>.

<FIG> shows an example embodiment of a radar system. The radar system includes a first radar device <NUM> that includes a UWB transmitter module <NUM>, and a second and a third radar device <NUM>, <NUM> that each include a UWB receiver module <NUM>, <NUM>. These modules can be considered as processors or can include processors.

The UWB transmitter module <NUM> has an antenna that transmits UWB signalling. Each of the UWB receiver modules <NUM>, <NUM> has an antenna that receives the UWB signalling from the UWB transmitter module <NUM>. As shown schematically in <FIG>, the UWB signalling can follow a direct path <NUM> between the antenna of the UWB transmitter module <NUM> of the antenna of the first radar device and the UWB receiver module <NUM> of the second radar device <NUM>. There can also be several reflective paths between the antenna of the UWB transmitter module <NUM> of the first radar device and the antenna of the UWB receiver module <NUM> of the second radar device <NUM>, via a target <NUM>. One such reflected path is shown in <FIG> with reference <NUM>. The direct path <NUM> will typically be the shortest path between the TX and RX antennas. Also, the direct path <NUM> is typically also the strongest (in that the UWB signalling that is received at the antenna of the UWB receiver module <NUM> of the second radar device <NUM>). As will be discussed in detail below, examples disclosed herein use the direct path for wireless synchronization of the CIRs of the different RXs.

Even if the UWB transmitter module <NUM> and the UWB receiver module <NUM> are started simultaneously (e.g., via an external trigger), and even if they share a clock (as shown in <FIG>), synchronization is still needed because device imperfections will cause a random shift of the start of each UWB receiver module <NUM> with respect to the UWB transmitter module <NUM>. This can lead to a misalignment of the CIRs. The imperfections may be due to one or more of:.

A hardware-based synchronization mechanism can address at least some of these issues. However, not all radar devices support such a sync mechanism, as discussed above, and there are various disadvantages associated with using wired synchronization.

<FIG> shows a plot of <NUM> channel impulse responses (CIRs) that are calculated by a UWB receiver module, with each CIR overlaid upon each other.

<FIG> shows the results for an implementation of a UWB radar system that comprises:.

Each CIR in <FIG> represents the results of a different run. The UWB receiver module is restarted for each run. Each peak that is visible in the plot of <FIG> represents the reception of UWB signalling from a UWB transmitter module over a direct path. (It is recalled that the UWB signalling received via the direct path is expected to have the highest power. ) Since the peak of each run that is shown in <FIG> occurs at a different time (as represented by the channel taps on the horizontal axis), <FIG> shows how the imperfections that identified above result in the RX start not being synchronized with the TX start.

<FIG> shows an example embodiment of a method for performing wireless synchronization for a multi-device UWB radar system that uses a shared clock (like the system in <FIG>).

In a relatively simple case, the radar system has a reference clock (e.g., <NUM>) that is shared among all devices. In general, this clock is driving the phase locked loops (PLLs) that generate digital clocks (e.g., for RX digital baseband) and radio frequency (RF) clocks / signals (e.g., LO signal, digital-to-analog converter clock, etc.). With the clock being shared, any drift and carrier frequency offsets between the PLLs on the TX and the RXs are eliminated.

At step <NUM>, the method involves a UWB receiver module wirelessly receiving UWB signalling from a UWB transmitter module. As discussed with reference to <FIG>, such UWB signalling can be received via a direct path and / or a reflected path.

At step <NUM>, a processor associated with the UWB receiver module determines a channel impulse response, CIR, of the wirelessly received UWB signalling.

<FIG> shows an example of a single CIR <NUM> (as opposed to the <NUM> CIRs that are shown overlaid with each other in <FIG>). The CIR <NUM> has a plurality of channel taps (represented by the horizontal axis) each having a tap-response-value (represented by the vertical axis). The CIR <NUM> has a peak <NUM> that corresponds to reception of UWB signalling via the direct path.

The generation of such CIRs is well known in the art. At a high level, it can relate to one frame that contains a symbol "S" that is repeated N times. This is shown in <FIG> and will be described in more detail below. In the receiver, all N symbols are averaged, yielding one "average symbol". This symbol, which comprises a transmitted code, is correlated against the transmitted code known to the receiver, thereby producing the CIR.

Returning to <FIG>, at step <NUM> the method identifies one or more features in the CIR and also identifies an associated channel tap. As will be discussed below, such features can be one or more predetermined features in the CIR that correspond to reception of the UWB signalling via a direct path from the UWB transmitter module.

Examples of features that can be identified include:.

At step <NUM>, once the one or more features in the CIR have been identified, an associated channel tap can then be determined. For instance, the associated channel tap may be the one that exhibits the identified feature (e.g., the one with the highest tap-response-value). Alternatively, the associated channel tap may be the one that has a predetermined relationship with the channel tap that exhibits the identified feature (e.g., the channel tap that is <NUM> channel taps after the one with the highest tap-response-value). Such an alternative arrangement can still enable the method of <FIG> to achieve its advantages, as will be appreciated from the discussion that follows.

Then, at step <NUM>, based on the channel tap that is associated with the identified feature in the CIR, the method synchronizes the UWB receiver module for reception of subsequent UWB signalling. Such synchronization can be performed in one of a number of different ways once the channel tap that is associated with the identified feature in the CIR is known. Assuming that each of a plurality of UWB receiver modules use the same synchronization method, then it does not matter what that method is.

Returning to <FIG>, each of the <NUM> channel taps of the CIR that are shown represent a transmission period symbol of the UWB transmitter module. In this example, each of these <NUM> channel taps (i.e., the entire CIR) is processed in order to identify the predetermined feature in the CIR and the associated channel tap. In <FIG>, the feature is the channel tap of the CIR <NUM> that has the highest (peak) tap-response-value <NUM> - which is tap number <NUM>.

The method in this example then synchronizes the UWB receiver module for reception of subsequent UWB signalling by determining a channel impulse response, CIR, of the received subsequent UWB signalling. However, the CIR for the subsequent UWB signalling comprises a set of channel taps based on the channel tap that is associated with the identified feature in the CIR, and the set of channel taps is a subset of the channel taps that together represent the transmission period symbol of the UWB transmitter module. That is, the CIR of the subsequent UWB signalling is not calculated for all of the channel taps (represented by the horizontal axis) - instead it is calculated for a subset of the channel taps (as represented by the box that is shown in <FIG> with reference <NUM>). Furthermore, the channel taps that are included in the subset are based on the channel tap that is associated with the identified feature in the CIR for the earlier UWB signalling. In the example of <FIG>, the subset of channel taps is the <NUM> taps that immediately follow the highest (peak) tap-response-value <NUM>.

Then, the method processes the tap-response-values of the CIR of the received subsequent UWB signalling (which is only a subset of the full range of channel taps) to identify any reflected versions of the subsequent UWB signalling.

In this way the CIR can be computed for all N = <NUM> taps of a first instance of the UWB signalling (for example the first UWB signalling that is received after start-up), and the CIR peak is determined. As the CIR peak corresponds to the direct path, any reflection from the actual target would come after the peak. Thus, detecting the CIR peak implies synchronization between TX and RX because the identification of any reflected versions of subsequent instances of the UWB signalling can be restricted to a subset of the channel taps that are expected to include it.

<FIG> shows a first example of a CIR that is calculated for subsequent UWB signalling, in this example for <NUM> of the total <NUM> channel taps. <FIG> shows a second example of a CIR that is calculated for subsequent UWB signalling, in this example for <NUM> of the total <NUM> channel taps.

Methods of identifying reflected versions of UWB signalling are well-known in the art and will not be described in detail here. Nonetheless, <FIG> is an example of a CIR <NUM> where a reflected version is not identified. <FIG> is an example of a CIR <NUM> where a reflected version is identified, as represented by the peak <NUM> at a distance of <NUM>. As is known in the art, the index of the channel tap at which the reflected UWB signalling is identified corresponds to the distance to the target that reflects the UWB signalling. For instance, in one example each channel tap can represent <NUM> metres. Therefore, it will be appreciated that the number of channel taps that included in the CIR of the subsequent UWB signalling will define the maximum range of the radar system.

Synchronizing the UWB receiver module in this way can advantageously account for any timing offsets between the UWB transmitter module and the UWB receiver module (that are unpredictable, as described with reference to <FIG>), and can also reduce the processing that is required to identify any reflected versions of the subsequent UWB signalling because the CIR does not need to be calculated for all of the channel taps. In some applications, this can limit the amount of data that is streamed to a host for identifying reflected versions of the subsequent UWB signalling.

<FIG> shows a graphical representation of how (initial) UWB signalling and then subsequent UWB signalling is processed according to the method of <FIG>.

UWB radar frame <NUM><NUM> in <FIG> is an example of (initial) UWB signalling. Frame <NUM><NUM> is processed to determine a CIR with N taps, which represents a complete transmission symbol. In <FIG>, N = <NUM>. The CIR with N taps is then processed to detect a CIR peak (as an example of a feature), in this example the strongest peak.

UWB radar frames <NUM> and <NUM><NUM>, <NUM> are then received after frame <NUM><NUM>. UWB radar frames <NUM> and <NUM><NUM>, <NUM> are examples of subsequent UWB signalling. UWB radar frames <NUM> and <NUM><NUM>, <NUM> are then processed to determine a CIR with M taps around the peak that was identified in the CIR for frame <NUM><NUM>, where M is less than N. In this way, the CIRs for frames <NUM> and <NUM><NUM>, <NUM> include taps that are a subset of the CIR for frame <NUM><NUM>. Extracting the M taps in this way represents the synchronization.

<FIG> shows an example embodiment of a method for performing wireless synchronization for a multi-device UWB radar system where the radar devices use independent clocks (like the system in <FIG>).

As the independent clocks will not be exactly the same, there will be a drift as well as a timing and frequency offset between the PLLs on the TX and the RXs. This can include:.

Drift and offsets should be compensated before RX radar operation can start. For example, the CFO may be compensated by retuning the RF PLL.

In the example of <FIG>, an initial synchronization operation is performed based on UWB ranging signalling before the synchronization that is shown in <FIG> is performed.

At step <NUM>, the method receives UWB ranging signalling from the UWB transmitter module.

<FIG> shows the UWB frame format according to IEEE <NUM>. <NUM> (which is a relevant UWB standard).

The general ranging format for secure ranging, as shown in <FIG> includes:.

In the middle part of <FIG>, the preamble is expanded to show that it includes a plurality of symbols "S". A symbol in the PREAMBLE is repeated N times (e.g., N = <NUM>). Each symbol contains a code sequence of length L (e.g., L = <NUM>). A code sequence Z may be binary (+<NUM>/-<NUM> sequence) or ternary (+<NUM>/<NUM>/-<NUM> sequence), where:.

In between the pulses, there may be additional <NUM>'s (i.e., no pulse).

In the ranging mode, that is for UWB ranging signalling, the full frame is used. In the radar mode, that is for UWB radar signalling, only the PREAMBLE is used. The number of repeated symbols may be larger in the radar mode than it is for the ranging mode (e.g., <NUM> in radar vs. <NUM> in ranging).

Returning to <FIG>, at step <NUM> the method estimates, and compensates for, one or more frequency and / or timing offsets. This can be especially well-suited to UWB ranging signalling because UWB ranging signalling includes more appropriate information than UWB radar signalling.

For example, at step <NUM>, the method can estimate a carrier frequency offset (CFO) by a phase / frequency tracking loop in the receiver digital baseband and can be compensated by retuning an RF PLL by a frequency amount corresponding to the determined CFO.

Similarly, at step <NUM>, the method can determine a timing offset (such as a sampling timing offset) using a timing tracking loop that can be used to set the sampling time to sample an UWB pulse at a maximum.

Further still, at step <NUM>, the method can determine a local oscillator phase offset using a phase tracking loop and can compensate for it by rotating the (complex-valued) CIR by a phase amount corresponding to the determined phase offset.

It will be appreciated that these are non-limiting examples of ways in which the method can process the UWB ranging signalling in order to estimate, and compensate for, one or more frequency or timing offsets.

At step <NUM>, the method wirelessly receives UWB radar signalling. In this example, the UWB radar signalling is processed after the UWB ranging signalling is processed at step <NUM> in order to estimate, and compensate for, one or more frequency or timing offsets. This reception of UWB radar signalling corresponds to the reception of UWB signalling at step <NUM> of <FIG>.

Then at step <NUM>, the method synchronizes the radar operation of the UWB receiver module based on timing information. This is a short-hand expression of the determination of a CIR, identification of a predetermined feature in the CIR and an associated channel tap, and synchronization steps that are shown as separate steps <NUM>-<NUM> in <FIG>. Therefore, <FIG> can be considered as an example method that includes the functionality of steps <NUM> and <NUM> in addition to the functionality of <FIG>.

Optionally, the processing at step <NUM> can also involve synchronizing the UWB receiver module for reception of subsequent UWB radar signalling based on the frequency and / or timing offsets that were estimated at step <NUM>. This is in addition to the synchronization of <FIG> that is based on the channel tap that is associated with the identified feature in the CIR.

In this way, the RX of one device wirelessly receives at least one UWB ranging signal (frame) transmitted from the TX of another device. In one example, the RX can then determine the time-of-arrival (ToA) corresponding to the direct path and estimate and compensate one or more frequency and / or timing offsets. Since the offsets are compensated, the RX can switch to radar operation and receive one or more radar signals from the TX. Therefore, the RX radar operation has been synchronized to the TX based on timing information. For example, the TX may have sent timing information (via the payload) to the RX during the initial ranging signalling such that the radar operation can start after the ranging operation.

Variations to the processing that is described with reference to some of the above examples include:.

For the example of <FIG>, which involves the use of independent clocks, the UWB ranging signalling may be sent:.

This can be beneficial because the CFO is unlikely to be static, and therefore repeating the estimation, and compensation for, frequency or timing offsets can advantageously be performed periodically or when required.

For the example of <FIG>, which involves the use of independent clocks, the UWB ranging signalling may be sent by an initiator (e.g., a key fob) that does not necessarily contain the UWB transmitter module that will be used for the radar operation. In addition, the UWB transmitter module that is used for transmitting UWB radar signalling radar may also include the functionality of a UWB receiver module that is synchronized with the initiator.

In general, any device of the multi-device radar systems disclosed herein may be a radar/ranging-capable device.

Examples described herein provide wireless synchronization between TX and RX in a multi-device radar system, comprising:.

The use of wireless synchronization for a multi-device UWB radar system described herein provides advantages over the use of wired synchronization. Synchronization can be performed in radar mode based on the direct path detected in a CIR, and optionally also using a ranging mode prior to the radar mode, in order to support both shared-clock and independent-clocks use cases.

In other examples, the set of instructions/methods illustrated herein, and data and instructions associated therewith are stored in respective storage devices, which are implemented as one or more non-transient machine or computer-readable or computer-usable storage media or mediums.

Example embodiments of the material discussed in this specification can be implemented in whole or in part through network, computer, or data-based devices and/or services.

Claim 1:
An ultra-wideband, UWB, receiver module (<NUM>, <NUM>) comprising:
an antenna for wirelessly receiving UWB signalling from a UWB transmitter module (<NUM>); and
a processor configured to:
determine a channel impulse response, CIR, of the wirelessly received UWB signalling, wherein the CIR comprises a plurality of channel taps each having a tap-response-value;
identify a predetermined feature in the CIR and an associated channel tap; and
based on the channel tap that is associated with the identified feature in the CIR, synchronize the UWB receiver module (<NUM>, <NUM>) for reception of subsequent UWB signalling;
characterized in that:
the plurality of channel taps of the CIR together represents a transmission symbol of the UWB transmitter module (<NUM>); and
the processor is configured to synchronize the UWB receiver module (<NUM>, <NUM>) for reception of subsequent UWB signalling by:
determining a channel impulse response, CIR, of the received subsequent UWB signalling, wherein:
the CIR comprises a set of channel taps based on the channel tap that is associated with the identified feature in the CIR, and wherein the set of channel taps is a subset of the plurality of channel taps that together represent the transmission symbol of the UWB transmitter module (<NUM>); and
each of the set of channel taps has a tap-response-value; and
processing the tap-response-values of the CIR of the received subsequent UWB signalling to identify any reflected versions of the subsequent UWB signalling.