Ultra-wideband calibration method, apparatus and chip

Abstract

Systems, devices, and methods for calibrating UWB sensing and ranging systems are disclosed. In one aspect, a method of calibrating at least one UWB device is disclosed. In an embodiment, the method includes receiving a first packet using a first power level; estimating a first channel impulse response from the first packet, wherein the first channel impulse response comprises at least one tap; and determining that a tap in the first channel impulse response is saturated. The method may further include based on the determining, receiving a second packet; estimating a second channel impulse response from the second packet, wherein the second channel impulse response comprises a first path position; and storing the first path position.

Description

Docket No.62306.128WO01 (P231429-WO-UTL) Ultra-Wideband Calibration Systems, Methods, and Devices Ciarán McElroy, Daniela Donati, and Marcas Ó Duinn CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Application No. 63 / 566,510, entitled “Ultra-Wideband Calibration Systems, Methods, and Devices” and filed on March 18, 2024, which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present disclosure relates generally to ultra-wideband wireless communication technology, and, more specifically to systems, methods, and devices for ultra-wideband sensing and two-way ranging. BACKGROUND

[0003] In ultra-wideband (UWB) sensing and two-way ranging (TWR) applications, it is typically desirable to obtain precise time of flight (ToF) information between a transmit antenna and a receive antenna for highly accurate distance, location, velocity, or position determinations. ToF information, and the associated determinations of various related quantities, such as distance, can become inaccurate if the distance between the transmit and receive antennas are not taken into account. The distance between the transmit and receive antennas affects ToF and related determinations, leading to inaccurate sensing and TWR applications. Thus, it can be important to calibrate a sensing or TWR system to account for the direct-path distance between antennas.

[0004] A dedicated calibration system operating with an external target at a known distance may possibly be used to determine a direct-path reference. However, when using a dedicated calibration system, each device typically has to be calibrated at production test and such calibration may be considerably expensive in terms of time, cost, and resources. Furthermore, due to hardware (HW) degradation, calibration may need to be repeated over time, which may not always be feasible and / or convenient.

[0005] Thus, there remains a need for effective ways to calibrate UWB sensing and TWR systems.Docket No.62306.128WO01 (P231429-WO-UTL) SUMMARY

[0006] Embodiments of the present disclosure include systems, devices, and methods for calibrating UWB sensing and ranging systems.

[0007] In an exemplary aspect, a method of calibrating at least one UWB device is disclosed. In an embodiment, the method includes receiving a first packet using a first power level; estimating a first channel impulse response from the first packet, wherein the first channel impulse response comprises at least one tap; and determining that a tap in the first channel impulse response is saturated. The method may further include based on the determining, receiving a second packet; estimating a second channel impulse response from the second packet, wherein the second channel impulse response comprises a first path position; and storing the first path position. In some embodiments, the second packet may be received using a second power level lower than the first power level.

[0008] In another exemplary aspect, an UWB communication apparatus is disclosed, wherein the UWB communication apparatus includes a receiver and a memory. In an embodiment, the receiver is configured to receive a first packet using a first power level; estimate a first channel impulse response from the first packet, wherein the first channel impulse response comprises at least one tap; determine that a tap in the first channel impulse response is saturated; and based on the determining, receive a second packet; and estimate a second channel impulse response from the second packet, wherein the second channel impulse response comprises a first path position. The memory is configured to store the first path position. In some embodiments, the second packet may be received using a second power level lower than the first power level.

[0009] In another exemplary aspect, a UWB chip is disclosed, wherein the UWB chip includes a receiver. In an embodiment, the receiver is configured to receive a first packet using a first power level; estimate a first channel impulse response from the first packet, wherein the first channel impulse response comprises at least one tap; determine that a tap in the first channel impulse response is saturated; and based on the determining, receive a second packet; and estimate a second channel impulse response from the second packet, wherein the second channel impulse response comprises a first path position. In some embodiments, the second packet may be received using a second power level lower than the first power level.

[0010] Additional aspects, features, and advantages of the present disclosure will become apparent from the following detailed description.Docket No.62306.128WO01 (P231429-WO-UTL) BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description, serve to explain the principles of the disclosure.

[0012] Fig.1 illustrates operation of an UWB device in sensing applications, according to some aspects of the present disclosure.

[0013] Fig.2 illustrates an example graph of the magnitude of a preamble channel impulse response (CIR) as a function of time, according to some aspects of the present disclosure.

[0014] Fig.3 illustrates a method of sensing operation, according to some aspects of the present disclosure.

[0015] Fig.4 is a block diagram of an example communication device, according to some aspects of the present disclosure.

[0016] Fig.5 is a more detailed block diagram of a receiver in an example communication device, according to some aspects of the present disclosure.

[0017] Fig.6 illustrates four examples of packet configurations as currently defined in the IEEE 802.15.4z standards, according to some aspects of the present disclosure.Docket No.62306.128WO01 (P231429-WO-UTL) DETAILED DESCRIPTION

[0018] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and / or steps described with respect to one embodiment may be combined with the features, components, and / or steps described with respect to other embodiments of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately.

[0019] Disclosed herein are systems, methods, and devices for determining a direct-path reference for UWB sensing and ranging systems. Such a direct-path reference between two antennas may also be referred to herein as a “zero-meter reference.” The zero-meter reference may be determined between two antennas residing on one UWB device or different UWB devices. In some embodiments, a reiterative zero-meter calibration method of UWB sensing or TWR may transmit and may receive one or more packets until a first path (FP) index can be logged without clipping in the channel impulse response (CIR). Thus, the present disclosure allows for a potentially more efficient determination of the zero-meter reference for a transmit antenna and a receive antenna or for at least two UWB devices performing TWR.

[0020] The disclosed embodiments may be applied in a wide variety of sensing and TWR use cases and a wide variety of sensing configurations and TWR configurations. In some embodiments, the terms “sensing” and “radar” are used herein consistent with the UWB arts to refer to ToF, distance, ranging, angle of arrival (AoA), and / or velocity calculations using some form of light waves, typically radio waves. For example, in some contexts, “sensing” and “radar” may have different connotations. In some contexts, “sensing” and “radar” may be used interchangeably.

[0021] In some embodiments, the zero-meter reference may generally refer to a distance or time interval used to determine error and / or delay in a ranging application comprising at least a transmit antenna and a receive antenna which are co-located. In some embodiments,Docket No.62306.128WO01 (P231429-WO-UTL) the zero-meter reference may be considered synonymous with a first path index and / or a first path. In some embodiments, the zero-meter reference may be considered synonymous with a direct path (DP). In some embodiments, the direct path may be used to calculate the zero- meter reference. For example, by considering the ToF required for a packet to travel the direct path compared to the ToF required for a packet to travel the target path, the device may calculate the ToF that would have been required for a packet to travel the target path if the transmit antenna and the receive antenna where theoretically located at the same position (i.e., zero meters apart). Thus, the transmit antenna and the receive antenna may be located in different locations without substantially affecting sensing operation.

[0022] In some embodiments, at least one transmit antenna and at least one receive antenna are co-located. The term “co-located” may refer in the UWB arts to a truly monostatic configuration in which a transmit antenna and a receive antenna are located at the exact same location or to a pseudo-monostatic configuration in which a transmit antenna and a receive antenna are a relatively short distance apart. Zero-meter calibration may be used in the pseudo-monostatic configuration to determine and account for the distance between a transmit antenna and a receive antenna in calibration. In some embodiments, a transmit antenna and a receive antenna are not co-located, which is typically referred to as a bistatic configuration. Zero-meter calibration may be used in a bistatic configuration to determine the distance between a transmit antenna and a receive antenna. Zero-meter calibration may be similarly applied to a multistatic configuration in which multiple transmit antennas and / or receive antennas are in operation to determine distance between the various antennas. In some embodiments, a transmit antenna and a receive antenna may be part of the same UWB device (e.g., a mono-source configuration). In some embodiments, a transmit antenna and a receive antenna may be part of different UWB devices (e.g., a multi-source configuration). In some embodiments, one UWB device may have more than one transmit antenna and / or more than one receive antenna. For example, an UWB device may have one transmit antenna and two receive antennas. In some embodiments, multiple UWB devices, each or in combination, may have more than one transmit antenna and / or more than one receive antenna. For example, some or all UWB devices from a group of UWB devices may each have one transmit antenna and two receive antennas.

[0023] In some embodiments, zero-meter calibration may be used to determine the antenna delay of an UWB device. In some embodiments, zero-meter calibration may be used to determine distance and / or time delay in TWR. For example, zero-meter calibration may beDocket No.62306.128WO01 (P231429-WO-UTL) used to determine the distance and / or time delay between a first ranging UWB and a second ranging UWB device. Then zero-meter calibration may be used to determine distance and / or time delay between the second UWB device and the first UWB device. For another example, zero-meter calibration may be used to perform TWR between more than two UWB devices in synchronization or in series.

[0024] Zero-meter calibration is especially useful in configurations in which a transmit antenna and a receive antenna are co-located in a same device and / or nearly at the same position relative to other objects in the environment. In this configuration, the transmit signal generally has a relatively high amplitude due to a high transmit power profile. When an analog-to-digital converter (ADC) receives the signal at the receive antenna, the high amplitude may cause clipping in the CIR. In some embodiments, zero-meter calibration may effectively and systematically vary the transmit power profile until a CIR can be analyzed without clipping.

[0025] The terms “packet” and “frame” are used herein consistent with the UWB arts to refer to basic units of transmission. For example, in some contexts, a packet may refer to a physical layer unit of transmission, and a frame may refer to a medium access control (MAC) layer unit of transmission. In some contexts, “packet” and “frame” may be used interchangeably.

[0026] In some embodiments, at least one device may provide a stand-alone, on-chip calibration of a zero-meter reference at the transmit antenna, mitigating or removing the need for a dedicated calibration system or method with an external target in production tests. In some embodiments, wherein a stand-alone, on-chip calibration is performed, at least one zero-meter calibration may be run in any sensing session, potentially providing a precise zero-meter reference for nearly any session, and, hence, a potentially more stable and potentially more accurate estimate of a target’s distance over time.

[0027] In some embodiments, at least one UWB device may provide a stand-alone, on- chip zero-meter calibration for an UWB sensing system. In some embodiments, zero-meter calibration mitigates or removes the need of a dedicated calibration system or method with at least one external target during a production test. In some embodiments, zero-meter calibration may be run in any sensing session.

[0028] In some embodiments, at least one UWB device may analyze the quality of a FP position of a preamble CIR. In some embodiments, at least one UWB device defines a zero- meter reference as a FP position of an unsaturated preamble CIR. In some embodimentsDocket No.62306.128WO01 (P231429-WO-UTL) wherein an UWB device’s antennas are relatively isolated from other objects, calibration may be more successful, efficient, and / or expedient. In some embodiments, at least one UWB device may combine FP positions detected in distinct UWB packet fields or sequences to improve the precision of a zero-meter reference. In some embodiments, at least one UWB device may probe a channel with a number of distinct transmit power levels at the preamble of a packet and potentially at least one other packet field of the same packet to potentially extract more channel information. In some embodiments, calibration comprises an antenna delay calibration for ranging applications, including UWB sensing, single-sided TWR (SS- TWR), and double-sided TWR (DS-TWR).

[0029] Fig.1 illustrates an example UWB sensing system 100, according to some aspects of the present disclosure. The UWB sensing system 100 includes a transmit antenna 101 and a receive antenna 102. A typical sensing scenario is illustrated in which a signal (such as a packet) is transmitted, and there is a direct path 104 (labeled “DP” in Fig.1) between the transmit antenna 101 and the receive antenna 102. In some embodiments, a transmit antenna 101 may transmit at least one packet. As shown, in an sensing application where there is an object 108 in the same environment as the transmit antenna 101, multiple versions of a transmitted packet are received at the receive antenna 102. For example, the receive antenna receives a transmission on a direct path 104, and also a reflection off an object 108 along a target path 106. Note that “spillover path” is a term used interchangeably with “direct path” in the relevant art.

[0030] In some embodiments, a signal received on a direct path may be used to determine a zero-meter reference. For example, by considering the ToF required for a packet to travel a direct path compared to the ToF required for a packet to travel a target path, the device may determine the ToF that would have been required for a packet to travel the target path if the transmit antenna and the receive antenna where theoretically located at the same position (i.e., zero meters apart). Thus, a sensing operation (e.g., to determine target distance from a device) may account for a distance between a transmit antenna and a receive antenna.

[0031] In some embodiments, in an UWB sensing system, a FP index may typically be detected as a direct path between a transmit antenna and a receive antenna (for example, see Fig.1). A FP index therefore may typically be used as a zero-meter reference when estimating at least one target distance. In some embodiments, if clipping occurs at the ADC, range bias may distort a CIR estimate in the accumulator, and, hence, a zero-meter estimate.Docket No.62306.128WO01 (P231429-WO-UTL)

[0032] Fig.2 illustrates an example graph of the magnitude of a preamble CIR as a function of time, according to some aspects of the present disclosure. The graph illustrates the magnitude 200 of an accumulated preamble CIR 204 determined from a received packet as a function of time in nanoseconds. At relatively high power, the first tap is saturated, causing the peak 206 to plateau. At relatively lower power, the first tap is not saturated causing the peak 208. Thus, the plateau 206 may cause some magnitude data to be lost above the plateau threshold, while the peak 208 potentially allows for all magnitude data to be analyzed. Thus, Fig.2 illustrates how, in some embodiments, range bias affects a FP index estimation which may lead to inaccurate range estimation(s). In the example in Fig.2, there is an offset of 1.53 ns between the reliable FP index at low transmit power and the one at high transmit power, which in this case, results in a corresponding 23 cm offset in distance calculation.

[0033] Fig.3 illustrates a method 300 for calibration of an UWB sensing system, according to some aspects of the present disclosure. For the sake of illustration, the variable “n” represents the transmit power profile index, the variable “N” represents the maximum transmit power profile index, the variable “m” represents the number of packets transmitted at transmit power profile index n, and the variable “M” represents the maximum number of packets transmitted at transmit power profile index n. In some embodiments, as the transmit power profile index increases (i.e., n = n + 1), the transmit power level typically decreases. However, the transmit power level may also be increased as needed to result in successful packet reception, as discussed further below. The method 300 for calibration may be run every sensing session so that a FP index is determined every sensing session, or the method 300 may be run periodically at some time interval with a FP index calculated and used for each time interval, regardless of the number of sensing sessions in each time interval, or the method 300 may be run in one sensing session to determine a FP index used for subsequent sensing sessions.

[0034] In some embodiments, as exemplified in Fig.3, a transmit power profile index n may be selected in step 302. Then, a transmit antenna may transmit a packet in step 304. Then, if a receive antenna correctly receives the packet m in step 306, the accumulator may determine if any taps in the CIR are saturated in step 330 and 332. If a receive antenna does not correctly receive the packet m in step 306, the calibration may proceed to step 308. If no taps are saturated in steps 330 and 332, the calibration may be considered complete, and a FP index may be logged in step 334. If any tap is saturated in steps 330 and 332, the calibration may proceed to step 308. In step 308, the calibration may determine if m equals M. If m doesDocket No.62306.128WO01 (P231429-WO-UTL) not equal M in step 308, m may be increased by one in step 310 and the calibration may return to step 304. If m equals M in step 308, the calibration may determine if n equals N in step 320. If n does not equal N in step 320, n may be increased by one, m may be reset to one in step 322, and the calibration may proceed again at step 302. If n equals N, the calibration may stop in step 340. Thus, the method in Fig.3 illustrates at least part of an embodiment of a zero-meter calibration.

[0035] In some embodiments, a subset of N transmit power profiles may be identified after a TX calibration. In some embodiments, the transmit power profiles may be low powers. In some embodiments, the transmit power profiles may be less than approximately -35 dBm transmitted in an approximately 500 MHz bandwidth.

[0036] In some embodiments, a device may transmit a packet at transmit power profile index 1. In some embodiments, the packet may be transmitted in sensing mode. If the receive antenna correctly received the packet, the packet may be analyzed to detect saturated taps in the preamble (of the UWB packet) accumulator. If the accumulator does not log any saturated taps, a FP index may be logged, and the routine may be indicated as complete. In some embodiments, if the accumulator does log at least one saturated tap, the packet may be transmitted again. That is, the process may restart at point 304 of Fig.3. In some embodiments, the process may be repeated a number of times. For example, a number of packets (a number represented by the variable “m”) may be transmitted via the transmit antenna, and correctly received packets may be analyzed (e.g., using the accumulator) to determine if any taps are saturated. Up to M transmissions may be attempted.

[0037] In some embodiments, if all the packet or packets transmitted at transmit power index 1 log at least one saturated tap, the device may restart calibration at a different power index. In some embodiments, the different transmit power level may typically be a reduced transmit power level. The adjusted transmit power level may be referred to as transmit power profile index 2, for example. In some embodiments, the transmit power level may be reduced by regular intervals or by random intervals. In some embodiments, the transmit power level may be reduced by approximately 3 dBm. In some embodiments, the device may repeat this process one or more times. That is, the device may transmit a packet or a number of packets at successively reduced transmit power levels and may analyze any correctly received packets with the accumulator to determine if any taps are saturated. In some embodiments, the number of times the transmit power level has been reduced may be represented by theDocket No.62306.128WO01 (P231429-WO-UTL) variable “n,” for example. In some embodiments, the number of reductions (n) may be limited to a finite number, for example, up to N reductions in the transmit power level.

[0038] In some scenarios, the power level of the initial power profile (n=1) may be sufficiently low that none of the M packets transmitted at the power level are successfully received (e.g., as determined in decision block 306). In this case, power may be increased in subsequent transmissions (e.g., in other power profiles) until packets are received correctly.

[0039] In some embodiments, a device detects saturated taps by comparing a tap in an accumulator to a defined or pre-defined threshold. For example, the magnitude of an Ipatov accumulator may be represented by the variable “z,” the pulse repetition frequency may be represented by the variable “PRF,” the number of symbols accumulated by the accumulator adjusted may be represented by the variableand the detection threshold may be represented by the variable “T”. ^ ^^^ ^ ^may vary depending on the packet format and / or configuration. In some embodiments, the detection threshold may be set heuristically to T = 0.75. In some embodiments, saturated taps may be detected by the following formulae: ^ ^^^^^^^ ^^^^^ ^^^ ^

[0040] In some embodiments, the device may normalize the accumulator. The normalized magnitude of the Ipatov accumulator may be represented by the variable “^^^^^.” The normalized magnitude of the Ipatov accumulator may be calculated by the following equation:

[0041] In some embodiments, the device may determine if any taps exceed (or are greater than) a threshold or a defined or pre-defined threshold. For example, this process maybe represented by the following formulae: ^^^^^^^^^ ^ ^^^^^^^^^^^^^^^ ^^ ^^

[0042] In some embodiments, a device may analyze CIR estimates obtained from any packet field and / or packet sequence, such as the start of frame delimiter (SFD), the physical layer (PHY) header (PHR), the PHY Payload, and / or the scrambled timestamp sequence (STS). In some embodiments, the device may combine FP positions obtained from the preamble and / or any other packet field(s) or packet sequence(s) to potentially further improve the precision of a zero-meter reference. These embodiments may be particularly suited for a direct path distortion induced by a strong reflection from an object relatively close to an antenna’s sensor, for example.Docket No.62306.128WO01 (P231429-WO-UTL)

[0043] In some embodiments, a device may transmit a packet with at least two different transmit power levels. One transmit power level may be applied to the preamble, while the other transmit power level may be applied to any other packet field(s) and / or packet sequence(s) in the same packet or in a different packet. In some embodiments, analysis of respective CIR estimates of the different packet field(s) and / or different packet sequence(s) may provide more channel information.

[0044] In some embodiments, a zero-meter calibration routine may be employed to calibrate antenna delay in ranging applications, such as SS-TWR applications and DS-TWR applications. Since UWB devices may typically be very precise, even minimal antenna delay may impact ranging calculations. In some TWR embodiments, a first device may transmit a packet from its transmit antenna to the receive antenna of a second device. After an undefined, defined, or pre-defined time interval, the second device may transmit the packet from its transmit antenna to the receive antenna of the first device. In some embodiments, the receive antennas of the first and second devices may experience clipping in the ADC, preventing an accurate two-way ranging calculation. In some embodiments, the first device may transmit a packet at transmit power profile index n. Then the second device may receive the packet and analyze the packet to detect saturated taps in the preamble accumulator. If no taps are saturated, the TWR process may proceed as normal. If any tap is saturated, the second device may transmit the packet back to the first device, indicating that the ranging failed. Then, in some embodiments, the first device may transmit another packet or a number of packets to the second device at the same transmit power profile index n. If any packet has no saturated taps, the TWR process may proceed as normal. If all the packets have at least one saturated tap, the second device may transmit the number of packets back to the first device, indicating that the ranging failed for all of the packets. Then, in some embodiments, the first device may transmit a packet at transmit power profile index n+1 and may proceed with the same calibration routine as applied to transmit power profile n. In some embodiments, this process may be repeated for a number of transmit power profile indices until the accumulator of the second device receives no saturated taps or until the maximum value of n is reached (i.e., N).

[0045] Fig.4 is a block diagram of an example communication device 400, according to some aspects of the present disclosure. The communication device 400 may be capable of operating in any of the sensing configurations presented herein. For example, the communication device 400 may represent one or more of the devices in Fig.1. In thisDocket No.62306.128WO01 (P231429-WO-UTL) embodiment, the communication device 400 comprises a receive antenna 402, a transmit antenna 410, a transceiver 408, a processor 404, and a memory 406. In this embodiment, the transceiver 408 includes a receiver 420 and a transmitter (not shown), wherein the transmitter includes an amplifier 412 or other circuitry controlled by the communication device 400 for adjusting the transmit power level to achieve the transmit power profiles / levels discussed with respect to the flowchart in Fig.3. In some embodiments, the transceiver 408 is configured to transmit a packet or set of packets via the transmit antenna 410, and the transceiver 408 is configured to receive the reflected packet or set of packets via the receive antenna 402 and the receiver 420. The received packet or set of packets may be stored in memory 406. The processor 404 may be used to convert the packet data to other formats. In some embodiments, the other formats may also be stored in the memory 406. In some embodiments, the transceiver 408 may be implemented using a combination of separate transmitter and receiver circuitry (such as analog circuitry) that are connected to other circuitry, such as the processor 404 or other circuitry, for performing baseband processing. In other embodiments the communication device 400 may include more than two antennas and the selection of which antenna(s) is / are used in transmission and which antenna(s) is / are used for reception may be dynamically controlled by the processor 404. In such embodiment, the use of multiple antennas may provide multiple snapshots of the reflections from the environment which may be then combined by the processor to get a better CIR.

[0046] The transceiver 408 may implement UWB communication capability, such as for transmitting and / or receiving UWB packets, such as described with respect to Fig.3. The communication device 400 may represent a smartphone or other device, that also implements Bluetooth, Wi-Fi, cellular, and / or other communication capability, such as by including one or more chips or processors that implement this capability. The transceiver 408 may be implemented as an integrated circuit, or chip.

[0047] Memory 406 may include one or more non-transitory storage devices that may include local and / or network accessible storage, a disk drive, a drive array, an optical storage device, a solid-state storage device such as a random access memory (RAM) and / or a read- only memory (ROM), a programmable ROM, a flash-updateable ROM, and / or the like. Such storage devices may be configured to implement any appropriate data storage, including without limitation, various file systems, database structures, and / or the like. The memory 406 may be used for storing programming instructions and other computer code for carrying out various steps described herein.Docket No.62306.128WO01 (P231429-WO-UTL)

[0048] Fig.5 is a more detailed block diagram of a receiver 420 in the example communication device 400, according to some aspects of the present disclosure. The receiver 420 represents an exemplary UWB receiver. As illustrated in Fig.5, the receiver 420 may include an analog radio frequency (RF) and baseband (BB) processing circuit 502 that takes a received RF signal (e.g., a received packet) and provides traditional front-end processing (e.g., amplification, filtering, down conversion to a BB frequency) and passes a baseband signal to an ADC 504. A sampled signal is passed to a correlator 506. The correlator 506 correlates the sampled signal with a known sequence, such as a preamble sequence. An example of a preamble sequence is one of known Ipatov sequences. After correlation, the resulting signal may be accumulated by an accumulator 508. This accumulated signal may then be used to provide a channel estimation from which the processor 404 may calculate a first path position, a time of arrival (ToA), and / or a distance to an object, such as object 108. Alternatively, the processor 404 may send information related to the accumulated signal back to a separate transmitter, if the transmitter is not co-located with the receiver, and the transmitter device may perform calculations to get a distance. Based on the calculated distance, location-based services may be provided.

[0049] The communication device 400, with receiver 420 implemented as shown in Fig. 5, may be used to implement the operations performed by receiving device explained with respect to Fig.3. For example, the accumulator discussed with respect to Fig.3 may be implemented as part of a receiver, such as receiver 420, and a FP index may be determined either within the receiver 420 or by a processor in conjunction with the receiver 420, such as processor 404. The FP index may be stored in a memory for later use in a ranging application, such as memory 406. The FP index may represent a ToF of a direct path between transmitting antenna 410 and receiving antenna 402, for example.

[0050] Fig.6 illustrates four examples of packet configurations as currently defined in the IEEE 802.15.4z standards, according to some aspects of the present disclosure. In each configuration, the illustrated arrow shows the ranging marker (RMARKER) reference position. The Synchronization (SYNC) field 608 is a known preamble (Ipatov sequence). Multiple Ipatov sequences are defined in the standard. The Ipatov sequences have perfect autocorrelation properties and good (but not perfect) cross-correlation properties since the various Ipatov sequences are not fully orthogonal.

[0051] The SFD (start of frame delimiter) field 610 is a known sequence to indicate the end of the preamble and the start of the frame. Depending on packet structure, the frame mayDocket No.62306.128WO01 (P231429-WO-UTL) be made up of a PHR (PHY header) 612, a structure including information about the PHY Payload 614; a PHY payload 614, the actual data conveyed by the physical frame; and an STS 616, a cryptographically strong sequence of pseudo-random pulses generated from a key (STS key).

[0052] A PHY packet structure begins with a SYNC field 608 followed by an SFD 610. In some embodiments, as shown in packet configuration 600, the SYNC field 608 and SFD 610 are followed by a PHR 612 followed by a PHY Payload 614. In some embodiments, as shown in packet configuration 602, the SYNC field 608 and SFD 610 are followed by an STS 616 followed by a PHR 612 followed by a PHY payload 614. In some embodiments, as shown in packet configuration 604, the SYNC field 608 and SFD 610 are followed by a PHR 612 followed by a PHY Payload 614 followed by an STS 616. In some embodiments, as shown in packet configuration 606, the SYNC field 608 and SFD 610 are followed by an STS 616.

[0053] SP0, SP1, SP2 and SP3 are four examples of packet configurations as defined by the 802.15.4z specification. The techniques disclosed herein leverage these existing packet structures, but the techniques are applicable to other packet structures, such as those defined by IEEE 802.15.4ab or any other packet structure for UWB transmission that includes a preamble, a SFD, a payload and any other additional content added to the physical packet.

[0054] Estimation and analysis of a CIR, which may involve, for example, aggregating the various responses from the environment, may be used to determine the distance to an object, and consequently deduce other information about the object, such as the object’s location and velocity. AoA may also be used to enrich the CIR information and consolidate the estimation of a user’s position.

[0055] In some sensing implementations, a CIR may be built on the analysis of an Ipatov sequence (located in the preamble). In some embodiments, the CIR may be built on the analysis of other parts of the packet and by combining the analysis of the various parts of the frame. In some embodiments, a sensing receiver (such as receiver 420) may use the STS 616 or PHY payload 614 to filter the responses and determine the wanted and unwanted received frames accordingly.

[0056] In this disclosure, “PRF” may be considered an acronym for “pulse repetition frequency,” RTLS may be considered an acronym for “Real Time Location System,” TX may be considered an abbreviation for “transmitter,” and RX may be considered an abbreviation for “receiver.”Docket No.62306.128WO01 (P231429-WO-UTL)

[0057] Persons skilled in the art will recognize that the apparatus, systems, and methods described above can be modified in various ways. Accordingly, persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.

Claims

Docket No.62306.128WO01 (P231429-WO-UTL) CLAIMS What is claimed is:

1. A method of calibrating at least one ultra-wideband (UWB) device, the method comprising: receiving a first packet using a first power level; estimating a first channel impulse response from the first packet, wherein the first channel impulse response comprises at least one tap; determining that a tap in the first channel impulse response is saturated; based on the determining, receiving a second packet; estimating a second channel impulse response from the second packet, wherein the second channel impulse response comprises a first path position; and storing the first path position.

2. The method of claim 1, wherein the determining that the tap in the channel impulse response is saturated comprises determining that a magnitude of the tap exceeds a threshold.

3. The method of claim 1, wherein the determining that the tap in the first channel impulse response is saturated comprises analyzing an output of an accumulator.

4. The method of claim 1, wherein the first packet comprises a preamble and at least one other field, and wherein the determining that the at least one tap in the first channel impulse response is saturated comprises analyzing the preamble and the at least one other field.

5. The method of claim 1, wherein the second packet is received using a second power level lower than the first power level, and wherein the method further comprises: estimating a target distance based on the first path position.

6. The method of claim 1, wherein the first packet comprises a first preamble, and wherein the first channel impulse response is based on correlating and accumulating over the first preamble.Docket No.62306.128WO01 (P231429-WO-UTL) 7. The method of claim 1, wherein the second channel impulse response comprises a second at least one tap, wherein the method further comprises: determining that none of the second at least one tap is saturated, wherein the first path position is determined based on the determining that none of the second at least one tap is saturated.

8. The method of claim 1, wherein the at least one UWB device comprises a UWB device comprising a transmit antenna and a receive antenna, wherein the first packet and the second packet are received using the receive antenna, wherein the method further comprises: transmitting the first packet by the transmit antenna at the first power level; and transmitting the second packet by the transmit antenna at the second power level.

9. The method of claim 1, wherein the first packet comprises a first preamble, wherein estimating the first channel impulse response comprises processing the first preamble in an accumulator to generate an output, and wherein the first channel impulse response is based on the output.

10. An ultra-wideband (UWB) communication apparatus comprising: a receiver configured to: receive a first packet using a first power level; estimate a first channel impulse response from the first packet, wherein the first channel impulse response comprises at least one tap; determine that a tap in the first channel impulse response is saturated; and based on the determining, receive a second packet; and estimate a second channel impulse response from the second packet, wherein the second channel impulse response comprises a first path position; and a memory configured to store the first path position.

11. The UWB communication apparatus of claim 10, wherein the determining that the tap in the first channel impulse response is saturated comprises determining that a magnitude of the tap exceeds a threshold.Docket No.62306.128WO01 (P231429-WO-UTL) 12. The UWB communication apparatus of claim 10, wherein the receiver comprises an accumulator, and wherein the determining that the tap in the first channel impulse response is saturated comprises analyzing an output of the accumulator.

13. The UWB communication apparatus of claim 10, wherein the second packet is received using a second power level lower than the first power level, and wherein the receiver is further configured to: receive a third packet; and estimate a third channel impulse response from the third packet, and wherein the UWB communication apparatus further comprises: a processor configured to estimate a target distance based on the third channel impulse response and the first path position.

14. The UWB communication apparatus of claim 10, wherein the second channel impulse response comprises a second at least one tap, wherein the receiver is further configured to: determine that none of the second at least one tap is saturated, wherein the first path position is determined based on the determining that none of the second at least one tap is saturated.

15. A wireless communication device comprising: the UWB communication apparatus of claim 10; and a cellular communication apparatus.

16. The UWB communication apparatus of claim 10, further comprising: an antenna; and a transmitter configured to: transmit the first packet at the first power level via the antenna; and transmit the second packet at a second power level lower than the first power level via the antenna.

17. An ultra-wideband (UWB) chip comprising: a receiver configured to: receive a first packet using a first power level;Docket No.62306.128WO01 (P231429-WO-UTL) estimate a first channel impulse response from the first packet, wherein the first channel impulse response comprises at least one tap; determine that a tap in the first channel impulse response is saturated; and based on the determining, receive a second packet; and estimate a second channel impulse response from the second packet, wherein the second channel impulse response comprises a first path position.

18. The UWB chip of claim 17, further comprising: an antenna; a transmitter configured to: transmit the first packet at the first power level via the antenna; and transmit the second packet at the second power level via the antenna.

19. A smartphone comprising: the UWB chip of claim 18; a memory configured to store the first path position; and a cellular communication chip.

20. The smartphone of claim 19, wherein the second packet is received using a second power level lower than the first power level, and wherein the receiver is further configured to: receive a third packet; and estimate a third channel impulse response from the third packet, and wherein the smartphone further comprises: a processor configured to estimate a target distance based on the third channel impulse response and the first path position.

21. The UWB chip of claim 17, wherein the receiver is further configured to: receive a third packet using a third power level; determine that the third packet is not successfully received; as a result of the determining that the third packet is not successfully received, receive a fourth packet at a fourth power level higher than the third power level; and estimate a third channel impulse response from the fourth packet, wherein the third channel impulse response comprises a first path position.

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