Method and apparatus for UWB-based distance measurement

Abstract

Described herein is a method of determining a distance between a UWB device and an object of interest, the method comprising: a) transmitting a pulsed signal from a transmitter of the UWB device, b) receiving a signal at a receiver of the UWB device, the signal comprising a reflection of the transmitted pulsed signal caused by the object of interest, c) determining a first distance estimate by applying a peak-based analysis to the received signal, d) determining a first confidence value associated with the first distance estimate, e) determining a second distance estimate by applying a phase-based analysis to the received signal, f) determining a second confidence value associated with the second distance estimate, and g) determining the distance between the UWB device and the object of interest based on the first distance estimate, the first confidence value, the second distance estimate, and the second confidence value. Further, a UWB apparatus comprising corresponding processing circuitry is described.

Description

Technical Field

[0001] The present disclosure relates to the field of methods and devices for distance measurement. More specifically, the present disclosure relates to methods of determining the distance between a UWB device and an object of interest. Furthermore, the present disclosure relates to a UWB device for determining the distance to an object of interest. Background Art

[0002] The UWB modem in the electronic device can be used as a pulse radar to measure the distance to a target or object of interest and / or track such a target / object. Thus, a short duration pulse is emitted and the reflection of the pulse is received. This reflection is captured as a change in the channel impulse response (CIR) measured by the receiver. In the case of strong coupling between the transmitter and the receiver located at the same location, the delay of the reflected signal can only be estimated after removing the coupled path. Since the coupled path cannot be accurately known empirically, the distance estimate is performed by looking at the delay when the peak energy is seen within the measurement window or by looking at the phase change over time after an accurate estimate of the coupled path. These two methods provide two independent distance estimates, a peak-based distance estimate and a phase-based distance estimate.

[0003] There are situations where one of the methods gives the correct result and the other does not. For example, when a new target suddenly appears at a significantly different (closer or farther) distance than the target being tracked, or when the target moves in a direction perpendicular to the radar's boresight, the phase-based estimate will not be accurate. On the other hand, the peak-based range estimate will be inaccurate in scenarios with weak targets (i.e., low signal-to-noise ratio (SNR)) or when shaking of the device causes the peak to change.

[0004] Therefore, relying on either of the peak-based and phase-based distance estimates may not provide robust and reliable performance with high accuracy during changing conditions.

[0005] Therefore, there may be a need for improved approaches to UWB radar-based distance measurement and tracking, specifically, approaches that can provide high accuracy in a wide variety of scenarios. Summary of the invention

[0006] This need may be met by the subject matter according to the independent claims. Advantageous exemplary embodiments of the disclosure are set out in the dependent claims.

[0007] According to a first aspect, a method for determining a distance between a UWB device and an object of interest is provided, the UWB device comprising a transmitter and a receiver. The method comprises: (a) transmitting a pulse signal from a transmitter of the UWB device, (b) receiving a signal at a receiver of the UWB device, the signal comprising a reflection of the transmitted pulse signal caused by the object of interest, (c) determining a first distance estimate by applying a peak-based analysis to the received signal, (d) determining a first confidence value associated with the first distance estimate, (e) determining a second distance estimate by applying a phase-based analysis to the received signal, (f) determining a second confidence value associated with the second distance estimate, and (g) determining the distance between the UWB device and the object of interest based on the first distance estimate, the first confidence value, the second distance estimate, and the second confidence value.

[0008] This aspect is based on the idea that both a first (peak-based) distance estimate and a second (phase-based) distance estimate are used together with respective (first and second) confidence values ​​associated with the (first and second) distance estimates to determine the distance between the UWB device and the object of interest that caused the reflection of the transmitted pulse signal. In other words, by relying on both the first distance estimate and the second distance estimate and their respective confidence values, accurate distance determination can be achieved. For example, in the case where one of the first distance estimate and the second distance estimate has a lower accuracy (and therefore a low confidence value) than the other of the first distance estimate and the second distance estimate, the latter can be relied on to accurately determine the distance, and vice versa.

[0009] In the present context, the term "peak-based analysis" may particularly denote an analysis of the received signal (also called channel impulse response or CIR) aiming to detect specific sampling times (also called taps) where peaks of received energy occur.

[0010] In the present context, the term "phase-based analysis" may particularly denote an analysis of the received signal (or CIR) aiming to detect phase changes corresponding to range changes.

[0011] In the present context, the term "confidence value" may specifically refer to a value, such as a numerical value, indicating a confidence level (or expected accuracy) of an estimate (e.g., a distance estimate). The confidence value may, for example, be a number between 0 and 1, where 0 indicates minimum (or no) confidence and 1 indicates maximum (or full) confidence.

[0012] According to an embodiment, the distance between the UWB device and the object of interest is determined as a weighted average of the first distance estimate and the second distance estimate.

[0013] In other words, the distance to the object of interest is determined by weighting the first distance estimate and the second distance estimate according to their respective (first and second) confidence values, whereby when the first confidence value and the second confidence value differ from each other, the resulting distance will rely more on the credible estimate and less on the uncredible estimate.

[0014] According to another embodiment, the first distance estimate is multiplied by a first weighting factor and the second distance estimate is multiplied by a second weighting factor, wherein each of the first weighting factor and the second weighting factor is based on the first confidence value and the second confidence value.

[0015] In other words, the first confidence value and the second confidence value are used to obtain the first weighting factor and the second weighting factor, which are used to weight the first distance estimate and the second distance estimate by multiplying the first distance estimate and the second distance estimate by the corresponding weighting factors, respectively.

[0016] According to another embodiment, the first weighting factor is calculated by dividing the first confidence value by the sum of the first confidence value and the second confidence value. In addition, or alternatively, the second weighting factor is calculated by dividing the second confidence value by the sum of the first confidence value and the second confidence value.

[0017] Mathematically, this can also be expressed as follows:

[0018] w pk =P pk / (P pk +P ph )

[0019] w ph =P ph / (P pk +P ph )

[0020] Here, w pk represents the first (or peak-based) weighting factor, w ph represents the second (or phase-based) weighting factor, P pk represents the first (or peak-based) confidence value, and P ph Represents the second (or phase-based) confidence value.

[0021] The resulting (or fused) distance d to the object of interest f Then it can be calculated as d f =w pk ·d pk +w ph ·d ph , where d pkrepresents the first (or peak-based) distance estimate, and d ph represents the second (or phase-based) distance estimate.

[0022] According to another embodiment, determining the first confidence value comprises determining a first SNR value associated with the first distance estimate.

[0023] Specifically, the first SNR value may be determined by measuring the signal power in a window around the tap corresponding to the first (peak-based) range estimate and dividing this signal power by the power measured around all other taps.

[0024] According to another embodiment, determining the second confidence value comprises determining a second SNR value associated with the second distance estimate.

[0025] Specifically, the second SNR value may be determined by measuring the signal power in a window around the tap corresponding to the second (phase-based) range estimate and dividing this signal power by the power measured around all other taps.

[0026] In some cases, the taps used to determine both the first SNR value and the second SNR value may be different, in other cases they may be the same.

[0027] According to another embodiment, the method further comprises: determining at least one quality indicator associated with at least one of the first distance estimate and the second distance estimate; and adjusting at least one of the first confidence value and the second confidence value based on the at least one quality indicator.

[0028] In other words, the at least one quality indicator may be used as an auxiliary measure for adjusting the first confidence value and / or the second confidence value. For example, the at least one quality indicator may reflect the stability or quality of the first confidence value or the second confidence value compared to previous measurements. Thereby, the resulting distance determination may be more accurate.

[0029] According to another embodiment, the at least one quality indicator includes at least one of the following: (a) the variance of the first distance estimate over a predetermined number of measurement windows, (b) the variance of the second distance estimate over a predetermined number of measurement windows, (c) a Doppler-based movement indicator associated with the first distance estimate, (d) a Doppler-based movement indicator associated with the second distance estimate, (e) a movement indicator based on the monotonicity of the unwrapped phase during a predetermined number of measurement windows, (f) the variance of the unwrapped phase difference between consecutive measurement windows, (g) the variance of the difference between the first distance estimate and the second distance estimate, and (h) the variance of the radius of the circle of best fitting complex points during the phase-based analysis.

[0030] Option (a) utilizes the variance of the first distance estimate over a predetermined number of measurement windows (each measurement window typically comprising the transmission of a plurality of pulse signals and the reception of a corresponding number of reflections) as a quality indicator associated with the first distance estimate. In other words, if the variance of the first distance estimate over a number of measurement windows is high, then the quality indicator may be correspondingly set to low, thereby indicating that the first confidence value should be adjusted in a downward direction, i.e., to indicate a lower confidence than the initially determined confidence. On the other hand, if the variance of the first distance estimate over a number of measurement windows is low, then the quality indicator may be correspondingly set to high, thereby indicating that the first confidence value should be maintained or adjusted in an upward direction, i.e., to indicate a higher confidence than the initially determined confidence.

[0031] Option (b) is similar to option (a) discussed above, except that here the variance of the second distance estimate is utilized as a quality indicator associated with the second distance estimate. That is, if the variance of the second distance estimate over a number of measurement windows is high, then the quality indicator may be correspondingly set to low, thereby indicating that the second confidence value should be adjusted in a downward direction, i.e., to indicate a lower confidence than the initially determined confidence. On the other hand, if the variance of the second distance estimate over a number of measurement windows is low, then the quality indicator may be correspondingly set to high, thereby indicating that the second confidence value should be maintained or adjusted in an upward direction, i.e., to indicate a higher confidence than the initially determined confidence.

[0032] Option (c) relies on Doppler measurements to obtain a movement indicator associated with the first (peak-based) distance estimate. The movement indicator may, for example, indicate whether there is a high or low degree of movement (e.g., movement speed). In addition, the movement indicator may, for example, indicate the direction of movement, specifically, whether the object of interest is moving toward or away from the device. In the case of a high degree of movement (indicating that the movement is a range jump), the second confidence value may be reduced because phase-based measurements are known to be less reliable in such cases, and the first confidence value may be increased accordingly. However, the latter is not mandatory. In other cases, in the case of a low degree of movement, the second confidence value may be increased because phase-based measurements are known to be reliable in such cases.

[0033] Option (d) is similar to option (c) and differs only in that it relies on Doppler measurements to obtain a movement indicator associated with the second (phase-based) range estimate (rather than the first (peak-based) range estimate used in option (c). Other than that, the use of the corresponding movement indicator is similar or identical to that discussed above in connection with option (c).

[0034] According to option (e), the movement indicator is obtained based on the monotonicity of the unwrapped phase during several measurement windows. If the unwrapped phase is monotonic, i.e., it increases steadily or decreases steadily, then the quality of the second phase-based distance estimate can be considered high, and thus the second confidence value can be increased accordingly. On the other hand, if the unwrapped phase is not monotonic, i.e., it jumps up and down, then the quality of the second phase-based distance estimate can be considered low, and thus the second confidence value can be reduced accordingly.

[0035] According to option (f), the variance of the unwrapped phase differences between consecutive measurement windows may be considered as an additional quality indicator. If the variance is high, the quality of the second phase-based distance estimate may be considered low, and the second confidence value may be reduced accordingly. On the other hand, if the variance is low, the quality of the second phase-based distance estimate may be considered high, and the second confidence value may be increased accordingly.

[0036] According to option (g), the variance of the difference between the first (peak-based) distance estimate and the second (phase-based) distance estimate over several measurement windows is considered, preferably in combination with another quality indicator. More specifically, if the other of the quality indicators indicates that one of the first distance measurement and the second distance measurement is of low quality, then the variance of the difference according to option (g) may be considered as a confirmation of this low quality. Therefore, the corresponding confidence value may be further adjusted to reflect this variance. Alternatively, the variance of the difference between the first distance estimate and the second distance estimate may be considered as an indication that neither distance estimate should be considered particularly reliable.

[0037] Finally, option (h) provides a specific quality metric for the second (phase-based) distance estimate. The larger the variance of the radius of the circle of best-fit composite points, the lower the quality of the second (phase-based) distance estimate, and therefore the smaller the associated confidence.

[0038] According to another embodiment, the UWB device includes an additional receiver, and the method further includes: (a) receiving an additional signal at the additional receiver of the UWB device, the additional signal including a reflection of the transmitted pulse signal caused by the object of interest, (b) determining an additional first distance estimate by applying a peak-based analysis to the additional received signal, (c) determining an additional first confidence value associated with the additional first distance estimate, (d) determining an additional second distance estimate by applying a phase-based analysis to the additional received signal, and (e) determining an additional second confidence value associated with the additional second distance estimate, (f) wherein determining the distance between the UWB device and the object of interest is additionally based on the additional first distance estimate, the additional first confidence value, the additional second distance estimate and the additional second confidence value.

[0039] In other words, the additional receiver also receives a signal including reflections from the object of interest, and processes this signal in the same manner as the signal received by the receiver to determine additional first (peak-based) distance estimates and second (phase-based) distance estimates and corresponding additional first and second confidence values. These additional distance estimates and confidence values ​​are then included as additional information when determining the distance to the object of interest.

[0040] According to a second aspect, a UWB device for determining a distance to an object of interest is provided. The device comprises: (a) a transmitter configured to transmit a pulse signal, (b) a receiver configured to receive a signal, the signal comprising reflections of the transmitted pulse signal caused by the object of interest, and (c) a processing circuit system configured to: (d) determine a first distance estimate by applying a peak-based analysis to the received signal, (e) determine a first confidence value associated with the first distance estimate, (f) determine a second distance estimate by applying a phase-based analysis to the received signal, (g) determine a second confidence value associated with the second distance estimate, and (h) determine the distance to the object of interest based on the first distance estimate, the first confidence value, the second distance estimate, and the second confidence value.

[0041] This aspect is essentially based on the same idea as the first aspect discussed above, and provides a UWB device comprising a transmitter, a receiver and a processing circuit system capable of performing a method according to the first aspect or any of the exemplary embodiments discussed above. That is, by relying on both a first distance estimate and a second distance estimate and their respective confidence values, accurate distance determination can be achieved. For example, in the case where one of the first distance estimate and the second distance estimate has a lower accuracy (and therefore a lower confidence value) than the other of the first distance estimate and the second distance estimate, the latter can be relied on to accurately determine the distance, and vice versa.

[0042] According to further embodiments, the processing circuitry is configured to determine the distance to the object of interest as a weighted average of the first distance estimate and the second distance estimate.

[0043] In other words, the distance to the object of interest is determined by weighting the first distance estimate and the second distance estimate according to their respective (first and second) confidence values, whereby when the first confidence value and the second confidence value differ from each other, the resulting distance will rely more on the credible estimate and less on the uncredible estimate.

[0044] According to another embodiment, the processing circuit system is configured to multiply the first distance estimate by a first weighting factor and multiply the second distance estimate by a second weighting factor, wherein each of the first weighting factor and the second weighting factor is based on the first confidence value and the second confidence value.

[0045] In other words, the first confidence value and the second confidence value are used to obtain the first weighting factor and the second weighting factor, which are used to weight the first distance estimate and the second distance estimate by multiplying the first distance estimate and the second distance estimate by the corresponding weighting factors, respectively.

[0046] According to another embodiment, the processing circuit system is configured to calculate the first weighting factor by dividing the first confidence value by the sum of the first confidence value and the second confidence value. In addition, or alternatively, the processing circuit system is configured to calculate the second weighting factor by dividing the second confidence value by the sum of the first confidence value and the second confidence value.

[0047] Mathematically, this can also be expressed as follows:

[0048] w pk =P pk / / (P pk +P ph )

[0049] wph =P ph / (P pk +P ph )

[0050] Here, w pk represents the first (or peak-based) weighting factor, w ph represents the second (or phase-based) weighting factor, P pk represents the first (or peak-based) confidence value, and P ph Represents the second (or phase-based) confidence value.

[0051] The resulting (or fused) distance d to the object of interest f Then it can be calculated as d f =w pk ·d pk +w ph ·d ph , where d pk represents the first (or peak-based) distance estimate, and d ph represents the second (or phase-based) distance estimate.

[0052] According to another embodiment, determining the first confidence value comprises determining a first SNR value associated with the first distance estimate.

[0053] Specifically, the first SNR value may be determined by measuring the signal power in a window around the tap corresponding to the first (peak-based) range estimate and dividing this signal power by the power measured around all other taps.

[0054] According to another embodiment, determining the second confidence value comprises determining a second SNR value associated with the second distance estimate.

[0055] Specifically, the second SNR value may be determined by measuring the signal power in a window around the tap corresponding to the second (phase-based) range estimate and dividing this signal power by the power measured around all other taps.

[0056] In some cases, the taps used to determine both the first SNR value and the second SNR value may be different, in other cases they may be the same.

[0057] According to another embodiment, the processing circuit system is further configured to: (a) determine at least one quality indicator associated with at least one of the first distance estimate and the second distance estimate, and (b) adjust at least one of the first confidence value and the second confidence value based on the at least one quality indicator.

[0058] In other words, the at least one quality indicator may be used as an auxiliary measure for adjusting the first confidence value and / or the second confidence value. For example, the at least one quality indicator may reflect the stability or quality of the first confidence value or the second confidence value compared to previous measurements. Thereby, the resulting distance determination may be more accurate.

[0059] According to another embodiment, the at least one quality indicator includes at least one of the following: (a) the variance of the first distance estimate over a predetermined number of measurement windows, (b) the variance of the second distance estimate over a predetermined number of measurement windows, (c) a Doppler-based movement indicator associated with the first distance estimate, (d) a Doppler-based movement indicator associated with the second distance estimate, (e) a movement indicator based on the monotonicity of the unwrapped phase during a predetermined number of measurement windows, (f) the variance of the unwrapped phase difference between consecutive measurement windows, (g) the variance of the difference between the first distance estimate and the second distance estimate, and (h) the variance of the radius of the circle of best fitting complex points during the phase-based analysis.

[0060] Option (a) utilizes the variance of the first distance estimate over a predetermined number of measurement windows (each measurement window typically comprising the transmission of a plurality of pulse signals and the reception of a corresponding number of reflections) as a quality indicator associated with the first distance estimate. In other words, if the variance of the first distance estimate over a number of measurement windows is high, then the quality indicator may be correspondingly set to low, thereby indicating that the first confidence value should be adjusted in a downward direction, i.e., to indicate a lower confidence than the initially determined confidence. On the other hand, if the variance of the first distance estimate over a number of measurement windows is low, then the quality indicator may be correspondingly set to high, thereby indicating that the first confidence value should be maintained or adjusted in an upward direction, i.e., to indicate a higher confidence than the initially determined confidence.

[0061] Option (b) is similar to option (a) discussed above, except that here the variance of the second distance estimate is utilized as a quality indicator associated with the second distance estimate. That is, if the variance of the second distance estimate over a number of measurement windows is high, then the quality indicator may be correspondingly set to low, thereby indicating that the second confidence value should be adjusted in a downward direction, i.e., to indicate a lower confidence than the initially determined confidence. On the other hand, if the variance of the second distance estimate over a number of measurement windows is low, then the quality indicator may be correspondingly set to high, thereby indicating that the second confidence value should be maintained or adjusted in an upward direction, i.e., to indicate a higher confidence than the initially determined confidence.

[0062] Option (c) relies on Doppler measurements to obtain a movement indicator associated with the first (peak-based) distance estimate. The movement indicator may, for example, indicate whether there is a high or low degree of movement (e.g., movement speed). In addition, the movement indicator may, for example, indicate the direction of movement, specifically, whether the object of interest is moving toward or away from the device. In the case of a high degree of movement (indicating that the movement is a range jump), the second confidence value may be reduced because phase-based measurements are known to be less reliable in such cases, and the first confidence value may be increased accordingly. However, the latter is not mandatory. In other cases, in the case of a low degree of movement, the second confidence value may be increased because phase-based measurements are known to be reliable in such cases.

[0063] Option (d) is similar to option (c) and differs only in that it relies on Doppler measurements to obtain a movement indicator associated with the second (phase-based) range estimate (rather than the first (peak-based) range estimate used in option (c). Other than that, the use of the corresponding movement indicator is similar or identical to that discussed above in connection with option (c).

[0064] According to option (e), the movement indicator is obtained based on the monotonicity of the unwrapped phase during several measurement windows. If the unwrapped phase is monotonic, i.e., it increases steadily or decreases steadily, then the quality of the second phase-based distance estimate can be considered high, and thus the second confidence value can be increased accordingly. On the other hand, if the unwrapped phase is not monotonic, i.e., it jumps up and down, then the quality of the second phase-based distance estimate can be considered low, and thus the second confidence value can be reduced accordingly.

[0065] According to option (f), the variance of the unwrapped phase differences between consecutive measurement windows may be considered as an additional quality indicator. If the variance is high, the quality of the second phase-based distance estimate may be considered low, and the second confidence value may be reduced accordingly. On the other hand, if the variance is low, the quality of the second phase-based distance estimate may be considered high, and the second confidence value may be increased accordingly.

[0066] According to option (g), the variance of the difference between the first (peak-based) distance estimate and the second (phase-based) distance estimate over several measurement windows is considered, preferably in combination with another quality indicator. More specifically, if the other of the quality indicators indicates that one of the first distance measurement and the second distance measurement is of low quality, then the variance of the difference according to option (g) may be considered as a confirmation of this low quality. Therefore, the corresponding confidence value may be further adjusted to reflect this variance. Alternatively, the variance of the difference between the first distance estimate and the second distance estimate may be considered as an indication that neither distance estimate should be considered particularly reliable.

[0067] Finally, option (h) provides a specific quality metric for the second (phase-based) distance estimate. The larger the variance of the radius of the circle of best-fit composite points, the lower the quality of the second (phase-based) distance estimate, and therefore the smaller the associated confidence.

[0068] According to another embodiment, the device includes an additional receiver, which is configured to receive an additional signal, the additional signal including reflections of the transmitted pulse signal caused by the object of interest, and the processing circuit system is further configured to: (a) determine an additional first distance estimate by applying a peak-based analysis to the additional received signal, (b) determine an additional first confidence value associated with the additional first distance estimate, (c) determine an additional second distance estimate by applying a phase-based analysis to the additional received signal, (d) determine an additional second confidence value associated with the additional second distance estimate, and (e) further determine the distance to the object of interest based on the additional first distance estimate, the additional first confidence value, the additional second distance estimate and the additional second confidence value.

[0069] In other words, the additional receiver also receives a signal including reflections from the object of interest, and processes this signal in the same manner as the signal received by the receiver to determine additional first (peak-based) distance estimates and second (phase-based) distance estimates and corresponding additional first and second confidence values. These additional distance estimates and confidence values ​​are then included as additional information when determining the distance to the object of interest.

[0070] It should be noted that exemplary embodiments have been described with reference to different subject matters. Specifically, some embodiments have been described with reference to method-type claims, while other embodiments have been described with reference to apparatus-type claims. However, one skilled in the art will appreciate from the foregoing and the following description that, unless otherwise indicated, any combination of features relating to different subject matters, specifically a combination of features of a method-type claim with features of an apparatus-type claim, in addition to any combination of features belonging to one type of subject matter, is also disclosed with this document.

[0071] Aspects as defined above and further aspects of the present disclosure will be apparent from the examples of embodiment described hereinafter and are explained with reference to the examples of embodiment. Various aspects of the present disclosure will be described in more detail hereinafter with reference to examples of embodiment, to which, however, the present disclosure is not limited. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 A block diagram of a UWB device according to an exemplary embodiment of the present disclosure is shown.

[0073] Figure 2 Shown by Figure 1 2. Exemplary signals transmitted and received by the UWB device shown in FIG.

[0074] Figure 3 An exemplary channel impulse response (CIR) obtained after processing in a UWB device according to an exemplary embodiment of the present disclosure is shown.

[0075] Figure 4 A phasor representation of exemplary CIR values ​​according to an exemplary embodiment of the present disclosure is shown.

[0076] Figure 5 An SNR-based determination of a confidence value according to an exemplary embodiment of the present disclosure is shown.

[0077] Figure 6 Confidence values ​​and weighting factors determined during operation of a UWB device according to an exemplary embodiment of the present disclosure are shown.

[0078] Figure 7 A distance estimate determined during operation of a UWB device according to an exemplary embodiment of the present disclosure is shown.

[0079] Figure 8 A flow chart showing a method of determining a distance between a UWB device and an object of interest according to an exemplary embodiment of the present disclosure.

[0080] Fig. 9 A partial block diagram of a UWB device including multiple receivers according to further exemplary embodiments is shown. DETAILED DESCRIPTION

[0081] The illustrations in the drawings are schematic. It should be noted that in different figures, similar or identical elements have the same reference signs or have reference signs which differ only within the first digit.

[0082] Figure 1 A block diagram of a UWB device 1 according to an exemplary embodiment of the present disclosure is shown. The device 1 includes a transmitter (TX) 2 coupled to a transmitter antenna, a receiver (RX) 3 coupled to a receiver antenna, and processing circuitry 4 coupled to the transmitter 2 and the receiver 3. In operation, the transmitter transmits a pulse signal 5 toward an object or target 6 of interest, which causes reflections 7 to propagate back toward the device 1. In addition, there is a direct coupling path 8 between the transmitter 2 and the receiver 3. Therefore, the signal received at the receiver 3 includes both a signal portion received via the direct coupling path 8 and a signal portion corresponding to the reflection 7. This is Figure 2, where the transmitted pulse signal 5 is shown as a function of time in the upper half (labeled TX), and the received signal 9 is shown in the lower half (labeled RX). As can be seen, the received signal 9 includes a directly coupled pulse corresponding to the pulse signal 5. In addition, a reflected signal 7 with some delay and significantly lower amplitude is shown in the circled portion of the lower graph.

[0083] Typically, the transmitter 2 will send a series of pulses with constant spacing in time during a measurement window. The corresponding signal from the receiver 3 will be processed by the processing circuitry 4 in order to determine the distance between the device 1 and the target 6. This processing involves calculating the channel impulse response (CIR) by coherent integration of the transmitted pulses. More specifically, the CIR can be modeled as:

[0084]

[0085] The first item (s) (τ) is the coupling path assumed to be constant over time (static), and the second term depends on the distance d = (τ tgt c) The Doppler frequency f of the target at position c) / 2 d The reflected signal amplitude is ρ, and the transmitted pulse is p(τ).

[0086] In some embodiments, the apparatus 1 may include at least one further receiver. In such cases, the apparatus 1 may include at least one further receiver. Figure 1 The signal received by each of the resulting multiple receivers is processed in the same manner as the signal received by the receiver 3 shown in . For ease of description, the following discussion will only refer to one receiver. However, those skilled in the art will recognize that the present disclosure is equally effective for devices with any number of receivers. Having more receivers will provide more data, and thus provide even better results.

[0087] Figure 3 In a UWB device (eg, Figure 1 1 and discussed above. At least a portion of the processing has removed the portion of the CIR corresponding to the direct coupling 8 between the transmitter 2 and the receiver 3. As shown, the CIR 10 shows a substantial peak 11 at a time or tap 12 corresponding to a peak-based distance estimate (also referred to herein as a first distance estimate). The peak 11 may preferably be detected using a suitable algorithm such as CFAR (Constant False Alarm Rate).

[0088] Figure 4A phasor representation of an exemplary CIR value at a given tap is shown. As shown, the phasor representation consists of a static phasor 13 corresponding to the direct coupling path 8 and a moving phasor 14 corresponding to the reflection 7 from the object of interest 6. Once the static phasor 13 has been correctly estimated, the target movement can be measured by accumulating the phase change over time (corresponding to the movement of the endpoint C on the circle 15). Thus, a phase-based distance estimate, also referred to herein as a second distance estimate, is obtained.

[0089] According to the present disclosure, the two distance estimates, i.e., the first (peak-based) distance estimate and the second (phase-based) distance estimate, can be combined in order to obtain a more accurate distance measurement, in particular, a distance measurement that remains accurate under changing conditions and which therefore exhibits an improved level of robustness compared to a device that utilizes only estimates. More specifically, as will be discussed below, this is accomplished by determining a first confidence value associated with the first (peak-based) distance estimate and a second confidence value associated with the second (phase-based) distance estimate. The distance between the device 1 and the target 6 is then determined based on the first and second distance estimates and the first and second confidence values. In particular, the confidence values ​​can be used to determine the degree of reliance on each of the two distance estimates at any given time. In particular, this can involve the calculation of a weighted average, in which the weights applied to each of the first and second distance estimates are calculated from the first and second confidence values.

[0090] Figure 5 50 shows the SNR-based determination of confidence values ​​according to an exemplary embodiment of the present disclosure. More specifically, the graph 50 shows the SNR-based determination of confidence values ​​according to an exemplary embodiment of the present disclosure. Figure 3 , specifically, having a peak 11 at time / tap 12. In addition, graph 50 shows that window 16 has been arranged around tap 12, and thereby surrounds peak 11. By calculating the ratio between the signal energy within window 16 and the remaining CIR (e.g., the mean 17 over the remaining taps), a signal-to-noise ratio (SNR) that can be used as a confidence value is obtained. It should be noted that this technique can be used for both the first distance estimate and the second distance estimate to obtain corresponding first and second confidence values ​​based on SNR. In the phase-based case, window 16 is arranged depending on the tap corresponding to the phase-based distance estimate. In other embodiments, other techniques can be used to obtain corresponding SNR values.

[0091] Figure 6A graph 60 is shown of confidence values ​​and corresponding weighting factors determined during operation of a UWB device according to an exemplary embodiment of the present disclosure. More specifically, the graph 60 shows a first confidence value 18 for a peak-based distance estimate (labeled "Peak Confidence") and a second confidence value 19 for a phase-based distance estimate (labeled "Phase Confidence"). Additionally, the graph 60 shows a first weighting factor 20 (labeled "Peak Weight") and a second weighting factor 21 (labeled "Phase Weight"). More specifically, the first weighting factor 20 and the second weighting factor 21 are calculated as follows:

[0092] w pk =P pk / (P pk +P ph )

[0093] w ph =P ph / (P pk +P ph )

[0094] Here, w pk represents the first (or peak-based) weighting factor 20 (“peak weight” in graph 60 ), w ph represents the second (or phase-based) weighting factor 21 (“phase weight” in graph 60 ), P pk represents the first (or peak-based) confidence value 18, and P ph Represents the second (or phase-based) confidence value 19.

[0095] As shown, in the case where one of the two confidence values ​​18, 19 is low, the other is usually high, and a situation where both confidence values ​​are extremely low does not occur.

[0096] Figure 7 1 shows distance estimates determined during operation of the UWB device 1 and the resulting (or fused) distance and true distance (true value) for comparison. More specifically, a first (peak-based) distance estimate 22 labeled "peak distance" and a second (phase-based) distance estimate 23 labeled "phase distance" are shown. In addition, a resulting distance 24 (labeled "fused distance") is shown. By utilizing the techniques discussed above and in Figure 6 The weighting factors 20, 21 shown in FIG. 2 combine or fuse the first distance estimate 22 and the second distance estimate 23 to obtain a resulting distance 24. More specifically, the resulting (or fused) distance d to the object of interest is f 24 Calculated as a weighted average:

[0097] d f =w pk ·dpk +w ph ·d ph

[0098] Here, d pk represents the first (or peak-based) distance estimate 22, and d ph represents the second (or phase-based) distance estimate 23 .

[0099] Figure 7 The graph 70 in FIG. 2 also shows the actual distance (or true value) 25 for comparison. As can be seen, the resulting / fused distance 24 is generally very close to the actual distance 25, with only some minor and short-term deviations occurring when the second phase-based distance estimate has a low confidence level.

[0100] Figure 8 A method for determining a UWB device (eg, Figure 1 1) and the object of interest (e.g., Figure 1 Flowchart 800 of a method for determining a distance between targets 6).

[0101] At 810 , a pulse signal 5 is transmitted from a transmitter 2 of a device 1 .

[0102] At 812, a signal comprising reflections from an object of interest 6 is received at the receiver 3 (or at each receiver if the device comprises more than one receiver).

[0103] Next, the received signal is processed.

[0104] More specifically, at 814, a first distance estimate is determined by applying a peak-based analysis to the received signal.

[0105] At 816, a first confidence value is determined. The first confidence value is associated with the first (peak-based) distance estimate and indicates a confidence in the first distance estimate.

[0106] Thereafter, or in parallel with processing operations 814 and 816, at 818, a second range estimate is determined by applying a phase-based analysis to the received signal.

[0107] At 820, a second confidence value is determined. The second confidence value is associated with the second (phase-based) distance estimate and indicates a confidence in the second distance estimate.

[0108] At 822, a resulting distance to the object of interest is determined based on the first and second distance estimates and the associated first and second confidence values. For example, the confidence values ​​may be used to calculate a weighting factor, and the resulting distance may then be calculated as a weighted average of the first and second distance estimates.

[0109] Optionally, one or more quality indicators may be determined at 824 and then used at 826 to adjust the first confidence value and / or the second confidence value prior to determining the resulting distance to the object of interest at 822. More specifically, the quality indicator may be used as an auxiliary metric to strengthen or weaken the confidence of the first distance estimate and / or the second distance estimate.

[0110] Examples of such quality indicators include the following: (a) the variance of the first distance estimate over a predetermined number of measurement windows, (b) the variance of the second distance estimate over a predetermined number of measurement windows, (c) a Doppler-based motion indicator associated with the first distance estimate, (d) a Doppler-based motion indicator associated with the second distance estimate, (e) a motion indicator based on the monotonicity of the unwrapped phase during a predetermined number of measurement windows, (f) the variance of the unwrapped phase difference between consecutive measurement windows, (g) the variance of the difference between the first distance estimate and the second distance estimate, and (h) the variance of the radius of the circle of best fit composite points during phase-based analysis.

[0111] Fig. 9 FIG. 9 shows a partial block diagram 90 of a UWB device including multiple receivers according to another exemplary embodiment. More specifically, the UWB device includes a total of N RX Receivers 91, 92, 93 are located close to each other within the UWB device and are coupled to a processing unit 94. Each receiver 91, 92, 93 obtains a first (peak-based) distance estimate "peak distance", a first confidence value "peak confidence", a second (phase-based) distance estimate "phase distance" and a second confidence value "phase position confidence", and provides these estimates and confidence values ​​to the processing unit 94. The processing unit fuses or combines these values ​​by weighting the distance estimates according to the confidence values ​​in a manner similar to that described above in conjunction with a single receiver to obtain a resulting distance "combined distance". More specifically, the corresponding calculation includes calculating the first (peak-based) weighting factor and the second (phase-based) weighting factor for each receiver 91, 92, 93 as follows:

[0112]

[0113] Here, w pk (rx i ) indicates the receiver rxi The first (peak-based) weighting factor of ph (rx i ) indicates the receiver rx i The second (phase-based) weighting factor of pk (rx i ) indicates the receiver rx i The first (peak-based) confidence value of ph (rx i ) indicates the receiver rx i A second (phase-based) confidence value for .

[0114] Combination distance d f Then it is calculated as

[0115]

[0116] where d pk (rx i ) indicates the distance from the receiver rx i The first (peak-based) distance estimate of , and d ph (rx i ) indicates the distance from the receiver rx i A second (phase-based) distance estimate of .

[0117] It should be noted that the use of terms such as "upper", "lower", "left" and "right" only refers to the orientation of the corresponding drawings, unless otherwise indicated.

[0118] It should be noted that the term "comprising" does not exclude other elements or steps, and the use of the article "a" or "an" does not exclude a plurality. Moreover, elements described in connection with different embodiments may be combined. It should also be noted that the reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. A method for determining the distance between a UWB device and an object of interest, characterized in that: The UWB device includes a transmitter and a receiver, and the method includes: transmitting a pulse signal from the transmitter of the UWB device, receiving a signal at the receiver of the UWB device, the signal comprising a reflection of the transmitted pulse signal caused by the object of interest, determining a first distance estimate by applying a peak-based analysis to the received signal, determining a first confidence value associated with the first distance estimate, determining a second range estimate by applying a phase-based analysis to the received signal, determining a second confidence value associated with the second distance estimate, and The distance between the UWB device and the object of interest is determined based on the first distance estimate, the first confidence value, the second distance estimate, and the second confidence value.

2. The method according to claim 1, characterized in that The distance between the UWB device and the object of interest is determined as a weighted average of the first distance estimate and the second distance estimate.

3. The method according to claim 2, characterized in that The first distance estimate is multiplied by a first weighting factor, and the second distance estimate is multiplied by a second weighting factor, wherein each of the first weighting factor and the second weighting factor is based on the first confidence value and the second confidence value.

4. The method according to claim 3, characterized in that The first weighting factor is calculated by dividing the first confidence value by a sum of the first confidence value and the second confidence value, and wherein the second weighting factor is calculated by dividing the second confidence value by the sum of the first confidence value and the second confidence value.

5. The method according to any one of claims 1 to 4, characterized in that Determining the first confidence value comprises determining a first SNR value associated with the first distance estimate, and / or wherein determining the second confidence value comprises determining a second SNR value associated with the second distance estimate.

6. The method according to any one of claims 1 to 5, characterized in that Also includes: determining at least one quality indicator associated with at least one of the first distance estimate and the second distance estimate, and At least one of the first confidence value and the second confidence value is adjusted based on the at least one quality indicator.

7. The method according to claim 6, characterized in that The at least one quality indicator comprises at least one of the following: the variance of the first distance estimate over a predetermined number of measurement windows, the variance of the second distance estimate over a predetermined number of measurement windows, a Doppler-based movement indicator associated with the first distance estimate, a Doppler-based movement indicator associated with the second range estimate, a moving indicator based on the monotonicity of the unwrapped phase during a predetermined number of measurement windows, The variance of the unwrapped phase difference between consecutive measurement windows, the variance of the difference between the first distance estimate and the second distance estimate, and The variance of the radius of the circle that best fits the complex points during the phase-based analysis.

8. The method according to any one of claims 1 to 7, characterized in that The USB device comprises a further receiver, the method further comprising: receiving a further signal at the further receiver of the UWB device, the further signal comprising a reflection of the transmitted pulse signal caused by the object of interest, determining a further first distance estimate by applying a peak-based analysis to the further received signal, determining a further first confidence value associated with the further first distance estimate, determining a further second range estimate by applying a phase-based analysis to the further received signal, and determining a further second confidence value associated with the further second distance estimate, Wherein determining the distance between the UWB device and the object of interest is additionally based on the additional first distance estimate, the additional first confidence value, the additional second distance estimate, and the additional second confidence value.

9. A UWB device for determining the distance to an object of interest, characterized in that: The device comprises: a transmitter configured to transmit a pulse signal, a receiver configured to receive a signal including a reflection of the transmitted pulse signal caused by the object of interest, and processing circuitry configured to: determining a first distance estimate by applying a peak-based analysis to the received signal, determining a first confidence value associated with the first distance estimate, determining a second range estimate by applying a phase-based analysis to the received signal, determining a second confidence value associated with the second distance estimate, and The distance to the object of interest is determined based on the first distance estimate, the first confidence value, the second distance estimate, and the second confidence value.

10. The device according to claim 9, characterized in that The processing circuitry is configured to determine the distance to the object of interest as a weighted average of the first distance estimate and the second distance estimate.

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