Method, transponder and system for ultra-precise object tracking using radar in a multi-object environment

Abstract

Radar-based tracking systems can be used to improve the accuracy for detecting and tracking one or more objects of interest. In some examples, multiple radars implemented in a device can be used to transmit signals to and receive signals from the one or more objects of interest. To distinguish an object of interest from an undesired object, such as a user's hand, the object of interest can include a transponder that applies a delay element to a signal received from a radar and thereafter transmits the delayed return signal back to the radar. The delay produced by the delay element can separate return signals from undesired reflections and enable those signals to be distinguished. The clear identification of desired return signals can result in more accurate object distance determinations, more accurate triangulation, and improved position detection and tracking accuracy.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Patent Application No. 16 / 917,852, filed June 30, 2020, the contents of which are incorporated herein by reference in their entirety for all purposes. Technical Field

[0003] This disclosure relates generally to object sensing systems, and more specifically to the use of radar to detect and track one or more objects such as a stylus. Background Technology

[0004] Many types of input devices are currently used to perform operations in computing systems, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touchscreens, and so on. Specifically, touchscreens are popular due to their ease of operation, flexibility, and decreasing price. A touchscreen may include a touch sensor panel and a display device such as a liquid crystal display (LCD). The touch sensor panel may be a transparent panel with a touch-sensitive surface, and the display device may be partially or completely positioned behind the panel such that the touch-sensitive surface covers at least a portion of the visible area of ​​the display device. Touchscreens allow users to perform various functions by touching the touch sensor panel at locations typically indicated by the user interface (UI) displayed on the display device using a finger, stylus, or other object. Generally, a touchscreen can recognize touches and their locations on the touch sensor panel, and the computing system can then interpret the touch based on the displayed content at the time of the touch, and then perform one or more actions based on the touch. In the case of some capacitive touch sensing systems, a physical touch on the display is not required to detect the touch, and objects near the surface can be detected without actually touching the surface.

[0005] However, proximity sensing systems (systems capable of detecting both touched and hovering objects) often require sensor arrays spanning large surface areas for object detection, and the image quality of the display can be compromised when the proximity sensing array is placed on top of it. Furthermore, the object detection range of proximity sensing systems is typically limited, and the position and motion sensing resolution of these systems is usually constrained by the number and size of the sensing elements in the array. Due to these limitations, alternative systems using triangulation to detect objects, such as ultrasonic and radar sensing systems, have been developed. However, even these systems may suffer from insufficient position detection accuracy, for example, when very precise position detection with sub-millimeter accuracy is required for objects (e.g., styluses). Summary of the Invention

[0006] This disclosure relates to the use of radar-based tracking systems to detect and track one or more objects of interest (e.g., one or more styluses, fingertips of gloves) with improved accuracy. In some examples, multiple radars implemented in a device (e.g., a computer, tablet, etc.) can be used to transmit signals to and receive signals from one or more objects of interest. As used herein, the device includes, but is not limited to, portable and handheld electronic devices, small stand-alone units communicating with other electronic devices (whose primary function is to provide radar functionality at a remote location), fixed electronic devices, and larger environmental devices such as smart rooms or smart whiteboards. To distinguish the object of interest from undesirable objects (such as the hand of a user holding the object of interest), the object of interest may include a transponder that applies a delay element to the signal received from the radar or otherwise processes the signal and subsequently transmits a return signal back to the radar. In examples utilizing a delay element, as defined herein, the delay generated by the delay element can separate the return signal from reflections from other sources (e.g., hands, etc.) and makes it possible to distinguish the desired return signal from the undesirable reflection. In the example of processing signals received from radar, the object of interest performs match filtering on the received signals, and if a match is confirmed, a unique return signal is transmitted back to the radar. This unique return signal can be matched and correlated to filter out unwanted reflections. Clear identification of the desired return signal leads to more accurate object distance determination, more accurate triangulation, and ultimately improved position detection and tracking accuracy.

[0007] In some examples, the delay elements mentioned above can be implemented in the object of interest using analog delay (e.g., the electrical length of a cable) or digital delay (e.g., analog-to-digital converters (ADCs), digital logic, and digital-to-analog converters (DACs)) to delay the frequency-modulated (FM) signal received from the radar. In some examples, the FM signal can be a frequency-modulated continuous wave (FMCW) signal. In other examples utilizing FMCW signals, the delay elements can be implemented using carrier drift, where the frequency difference represents the desired delay. For example, the object of interest may include two phase-locked loops (PLLs) or other frequency sources separated by carrier drift. The received FMCW signal can be down-converted, up-converted, and transmitted back to the radar with the desired carrier drift. The radar processing circuitry can use the carrier drift between the transmitted and received signals, as well as the known characteristics of the FMCW signal, to determine the distance between the radar and the object of interest. The distance data from multiple radars can then be used to employ triangulation techniques to determine the object's location with high accuracy. In some examples, accuracy of 100 micrometers or better can be achieved.

[0008] Radar-based object tracking systems, such as those described above, can determine the position and pose of two-dimensional or three-dimensional objects of interest moving on a surface or in free space. Furthermore, if multiple objects of interest employ delay elements with unique delays, multiple radars in the object tracking system can simultaneously track multiple objects of interest, allowing for an improved collaborative experience. For example, such systems could allow multiple users in the same conference room (each with a stylus) to collaboratively edit, draw, or otherwise contribute ideas to a shared document being created or displayed on a device such as a smartboard or smart display. In another example, wearable devices such as gloves equipped with delay elements on one or more fingertips can provide one or more objects of interest (each fingertip with a delay element is an object of interest) for performing poses. Attached Figure Description

[0009] Figures 1A to 1H An example of an electronic device that can be utilized within a radar-based object tracking system for performing precise object tracking, according to the present disclosure, is shown.

[0010] Figure 2 An exemplary block diagram of a radar-based object tracking system according to an example of this disclosure is shown.

[0011] Figure 3 A block diagram of a radar unit according to an example of this disclosure is shown.

[0012] Figure 4 A laptop computer is shown as an example of a radar-based object tracking system utilized in accordance with this disclosure.

[0013] Figure 5 An example of a radar-based object tracking system according to this disclosure is shown, comprising an object of interest and multiple radars, wherein the object of interest includes a transponder having a delay element capable of creating an effective delay.

[0014] Figure 6 An example of a radar-based object tracking system according to this disclosure is shown, comprising an object of interest and multiple radars, wherein the object of interest includes a transponder having a delay element capable of creating an effective delay.

[0015] Figure 7 An example of a radar-based object tracking system according to this disclosure is shown, comprising an object of interest and multiple radars, wherein the object of interest includes a transponder having a delay element capable of creating an actual delay.

[0016] Figure 8An example of a radar-based object tracking system according to this disclosure is shown, comprising an object of interest and multiple radars, wherein the object of interest includes a transponder having a delay element capable of creating an actual delay.

[0017] Figure 9 An example of a radar-based object tracking system according to this disclosure is shown, comprising an object of interest and multiple radars, wherein the object of interest includes a transponder having a delay element capable of creating an effective delay.

[0018] Figure 10 A process for high-precision object tracking is illustrated according to an example of this disclosure.

[0019] Figure 11 An example of a radar-based object tracking system according to this disclosure is shown, comprising an object of interest including a transponder capable of receiving a predefined transmit signal from the radar and transmitting a unique return signal.

[0020] Figure 12 A process for high-precision object tracking, according to an example of this disclosure, is shown. Detailed Implementation

[0021] In the following description of various examples, reference will be made to the accompanying drawings, which form part of the following description, and specific examples that can be implemented are illustrated in the drawings by way of illustration. It should be understood that other examples may be used and structural changes may be made without departing from the scope of the various examples.

[0022] This disclosure relates to using radar-based tracking systems to detect and track one or more objects of interest (e.g., one or more styluses, fingertips of gloves) with improved accuracy. In some examples, multiple radars implemented in a device (e.g., a computer, tablet, etc.) can be used to transmit signals to and receive signals from one or more objects of interest. As used herein, devices include, but are not limited to, portable and handheld electronic devices, small stand-alone units communicating with other electronic devices (whose primary function is to provide radar functionality at a remote location), fixed electronic devices, and larger environmental devices such as smart rooms or smart whiteboards. To distinguish the object of interest from undesirable objects (such as the hand of a user holding the object of interest), the object of interest may include a transponder that applies a delay element to a signal received from radar or otherwise processes the signal and then transmits the return signal back to radar. As used herein, the term "transponder" includes a device (e.g., a repeater) that retransmits the same signal it receives (optionally with a delay) or a device that receives one signal and transmits another signal, wherein the received and transmitted signals do not need to be the same or related signals (e.g., the transmitted signal may not be the same signal as the received signal or a modified version of the received signal). Furthermore, as used herein, the term "delay element" includes elements that produce an actual delay (e.g., the electrical length of a cable) or elements that produce an effective delay (e.g., a frequency-shifted signal). In examples utilizing delay elements, the delay generated by the delay element can separate the returned signal from reflections from other sources (e.g., a hand, etc.) and achieve the distinction between desired returned signals and unwanted reflections. In an example of processing signals received from radar, the object of interest performs match filtering on the received signal, and if a match is confirmed, a unique returned signal is transmitted back to the radar, which can be matched and correlated to filter out unwanted reflections. Clear identification of the desired returned signal can lead to more accurate object distance determination, more accurate triangulation, and ultimately improved position detection and tracking accuracy.

[0023] In some examples, a delay element can be implemented in the object of interest using analog delay (e.g., the electrical length of a cable) or digital delay (e.g., an ADC, digital logic, and a DAC) to delay the FM signal received from the radar. In some examples, the FM signal can be an FMCW signal. (As used herein, unless otherwise stated, the abbreviation "FM" is used to denote either an FM or FMCW signal.) In other examples utilizing FMCW signals, the delay element can be implemented using carrier drift, where the frequency difference represents the desired delay. For example, the object of interest may include two PLLs or other frequency sources separated by carrier drift. The received FMCW signal can be down-converted, up-converted, and transmitted back to the radar with the desired carrier drift. The radar processing circuitry can use the carrier drift between the transmitted and received signals, as well as the known characteristics of the FMCW signal, to determine the distance between the radar and the object of interest. The distance data from multiple radars can then be used to employ triangulation techniques to determine the object's location with high accuracy. In some examples, an accuracy of 100 micrometers or better can be achieved.

[0024] Radar-based object tracking systems, such as those described above, can determine the position and pose of two-dimensional or three-dimensional objects of interest moving on a surface or in free space. Furthermore, if multiple objects of interest employ transponders including delay elements with unique delays, multiple radars in the object tracking system can simultaneously track multiple objects of interest, allowing for an improved collaborative experience. For example, such systems could allow multiple users in the same conference room (each with a stylus) to collaboratively edit, draw, or otherwise contribute ideas to a shared document being created or displayed on a device such as a smartboard or smart display. In another example, wearable devices such as gloves equipped with delay elements on one or more fingertips can provide one or more objects of interest (each fingertip with a delay element is an object of interest) for performing poses.

[0025] Figures 1A to 1H An example of an electronic device that can be utilized within a radar-based object tracking system for performing precise object tracking, according to the present disclosure, is shown. Figure 1A An exemplary mobile phone 102, according to an example of this disclosure, can be used within a radar-based object tracking system. Figure 1B An exemplary digital media player 104, which can be utilized within a radar-based object tracking system according to an example of this disclosure, is shown. Figure 1C An exemplary personal computer 106, which can be utilized within a radar-based object tracking system according to an example of this disclosure, is shown. Figure 1D An exemplary tablet computing device 108, which can be utilized within a radar-based object tracking system according to an example of this disclosure, is shown. Figure 1EAn exemplary wearable device 110 (e.g., a watch) that can be utilized within a radar-based object tracking system according to an example of this disclosure is shown. Figure 1F An exemplary smart board 112 (e.g., an interactive whiteboard) that can be utilized within a radar-based object tracking system according to an example of this disclosure is shown. Figure 1G An exemplary smart screen 114 (e.g., an interactive video screen) that can be utilized within a radar-based object tracking system according to an example of this disclosure is shown. Figure 1H An exemplary glove 116, according to an example of this disclosure, can be used within a radar-based object tracking system. It should be understood that... Figures 1A to 1H The exemplary device shown is provided by way of example, and other types of devices may be used within a radar-based object tracking system for tracking the movement of an object according to the example of this disclosure.

[0026] The aforementioned equipment can be used within a radar-based object tracking system to add object tracking capabilities to that system. Figure 1C As an example, a laptop computer 106 incorporated into a radar-based object tracking system can provide two-dimensional object tracking capabilities for objects of interest, such as a stylus moving across its touchscreen, trackpad, or keyboard. In other examples, the radar-based object tracking system can also provide three-dimensional object tracking capabilities for objects of interest, such as a stylus moving in space above or outside the laptop computer's touchscreen, trackpad, or keyboard. In yet another example, the radar-based object tracking system can also provide three-dimensional object tracking capabilities for multiple objects, such as multiple styluses moving in space above or outside the laptop computer's touchscreen, trackpad, or keyboard. In a particular example, a computing device can be configured to display or capture images of a group of people in a conference room, and each of those people can simultaneously use their own stylus to perform gestures on a desktop or in space or on a smart board or screen to draw or otherwise provide input or gestures, which then appear on the image being displayed or captured.

[0027] Figure 2 An exemplary block diagram of a radar-based object tracking system according to an example of this disclosure is shown. In some examples, the radar-based object tracking system may include a device 200 (e.g., corresponding to devices 102, 104, 106, 108, and 110 described above) and one or more styluses 236. Device 200 may include a plurality of radar units 208, a host processor 214, and a program memory 216. In some examples, device 200 may optionally include one or more of a radar controller 206, a touch controller 204, and a touchscreen 202. Although Figure 2The host processor 214, touch controller 204, and radar controller 206 are shown as separate functional blocks; however, in some examples, two or more of these blocks may physically reside in the same controller, processor, or chip. It should be emphasized that... Figure 2 This is merely an exemplary high-level representation, and the device 200 may include fewer, more, or different functional blocks.

[0028] In some examples, the host processor 214 may communicate with the radar controller 206 and optionally with the touch controller 204 to initiate or perform actions based on those communications. The radar controller 206 may control the operation of multiple radar units 208, perform processing on data provided by the radar units, and further transmit object tracking signals to the host processor 214 for further processing and operation. The touch controller 204 may provide stimulation signals to the touchscreen and may receive and process touch signals from the touchscreen, and may further transmit touch signals to the host processor 214 for further processing and operation. The host processor 214 may be connected to a program memory 216 and a display controller (not shown) to generate images on the touchscreen 202. The program memory 216 may include, but is not limited to, random access memory (RAM) or other types of memory or storage devices, watchdog timers, etc.

[0029] In some examples, the host processor 214 may receive object tracking information and / or touch information to identify free-space poses, two-dimensional poses, touch poses, commands, etc. The object tracking and / or touch information may be used by a computer program stored in program memory 216 to perform or initiate actions, including but not limited to moving objects such as cursors or pointers, scrolling or panning, adjusting control settings, opening files or documents, viewing menus, making selections, executing instructions, and operating drawing programs. The host processor 214 may also perform additional functions that may not be related to touch processing.

[0030] It should be noted that the program-controlled functions described herein can be performed by firmware stored in program memory 216 and executed by host processor 214 or other processors. This firmware may also be stored and / or delivered in any non-transitory computer-readable storage medium for use or in conjunction with an instruction execution system, apparatus, or device, such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from and to an instruction execution system, apparatus, or device. In the context of this document, "non-transitory computer-readable storage medium" can be any medium (excluding signals) that can contain or store programs for use or in conjunction with an instruction execution system, apparatus, or device. Non-transitory computer-readable storage media may include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices; portable computer disks (magnetic); random access memory (RAM) (magnetic); read-only memory (ROM) (magnetic); erasable programmable read-only memory (EPROM) (magnetic); portable optical discs (such as CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW); or flash memory (such as compact flash memory cards, secure digital cards); USB storage devices; Memory Sticks, etc.

[0031] This firmware can also be propagated in any transmission medium for use or in combination with an instruction execution system, apparatus, or device, such as a computer-based system, a processor-based system, or other system capable of retrieving and executing instructions from and with an instruction execution system, apparatus, or device. In the context of this document, "transmission medium" can be any medium that can transmit, propagate, or transfer a program for use or in combination with an instruction execution system, apparatus, or device. Transmission readable media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, or infrared wired or wireless transmission media.

[0032] Figure 3A block diagram of an FM radar unit 308 according to an example of this disclosure is shown. Radar unit 308 may include a radar integrated circuit (IC) 310, an antenna 312, and other components. In some examples, radar IC 310 may include digital logic 334, such as one or more processors 318, memory 320, digital receive logic 336, and digital transmit logic 338. In some examples, radar IC 310 may include analog circuitry, such as an amplifier 322 for receiving reflected or otherwise returned signals, an RF mixer 324, an RF PLL or frequency source 326, an intermediate frequency (IF) bandpass filter 328, a low-noise amplifier 340, a transmit driver 342, an IF mixer 344, an IF PLL or frequency source 350, a low-pass filter 346, an ADC 330, a DAC 348, and a power amplifier 332 for transmitting signals. Radar IC 310 enables the sensing of the position and movement of an object, such as a stylus. In some examples, radar IC 310 may be an FM (but not a continuous wave) radar. In other examples, radar IC 310 can be an FMCW radar operating between 3 GHz and 150 GHz. In some examples, radar IC 310 can be a 60 GHz FMCW radar. It should be emphasized that... Figure 3 This is merely an exemplary high-level representation, and radar unit 308 may include fewer, more, or different components and functional blocks.

[0033] Figure 4 A laptop computer 400, according to an example of this disclosure, is used within a radar-based object tracking system. Figure 4 In the example, the laptop computer 400 includes three radars 402, and a stylus 404 is positioned on the surface of the laptop computer. To track the position of the stylus 404, each radar 402 may emit a signal at a specific frequency and use reflections from the tip of the stylus to measure its distance to the tip (e.g., R1, R2, and R3, respectively). A triangulation algorithm (e.g., a system of equations) can then be applied to the measured distances to determine the position of the stylus tip. However, each radar 402 will also detect reflections from other objects, such as reflections from the user's hand, which may result in the calculation of additional distances (e.g., R1', R2', and R3', respectively). These undesirable reflections should be minimized to obtain optimal distance measurements and ultimately accurate position and movement determination.

[0034] To distinguish reflections from objects of interest from undesirable objects, some examples of this disclosure employ transponders with delay elements within the object of interest. By delaying the signal returned from the object of interest by a certain amount of time, the returned signal can be temporally separated from reflections from undesirable objects. Although reflections from the object of interest may occur in addition to reflections from undesirable objects, reflections from the object of interest can be treated like reflections from undesirable objects, and can be distinguished and ignored to support the desired delayed signal returned from the object of interest. By the time the desired delayed return signal is finally received, the undelayed undesirable reflections can be sufficiently temporally separated to make distinction possible. For example, if the actual distance from the radar to the stylus tip is 0.5 m and the return signal from the stylus tip is delayed by a time equal to 10 m, the delayed return signal will be 40 * log(10 m / 0.5 m) = 52 dB stronger than the undesirable reflection from the undesirable object at a distance of 10 m. Generally, in some examples of this disclosure, the delay can be selected such that the signal-to-noise ratio (SNR) of the desired delayed return signal to the undesired reflection is greater than or equal to a predetermined (and in some examples selectable) value. Additionally, generating the desired return signal from the object of interest allows for amplification of the return signal without amplifying noise from the undesired reflection. This amplification can be useful because the amplitude of the received signal may be relatively small due to path loss.

[0035] Other examples of this disclosure employ a transponder within the object of interest that matches and identifies predefined signals received from the radar and transmits a unique return signal back to the radar. The radar then matches and identifies the unique return signal from the object of interest and correlates it to filter out unwanted reflections. The return signal can be used to calculate the distance between the object of interest and the radar, which can then be used with distance measurements from other radars to perform object tracking.

[0036] In some examples, the radar locations on the device can be selected to maximize the ability of the radar array to detect one or more objects of interest in two or three dimensions. For example, if the goal is to detect objects of interest in two dimensions only on the surface of the device, two radars can be used on that surface, although more than two radars can also be used. In some examples, if the goal is to detect objects of interest in three dimensions in the space above the surface of the device, three or more radars can be used on that surface. In some examples, if the goal is to detect one or more objects of interest in three dimensions in the space outside the device, multiple radars can be used at different locations on the device to maximize the ability of those radars to detect objects of interest.

[0037] Figure 5An example of a radar-based object tracking system 500 according to this disclosure is shown, comprising an object of interest 502 (e.g., a stylus) and multiple radars 504, the object of interest including a transponder with a delay element 510 capable of creating an effective or actual delay. Figure 5 In one example, the transponder also includes a low-noise amplifier (LNA) 506 that receives an FM signal from one of the radars in radar 504 via a receive (Rx) antenna, and a power amplifier (PA) 508 that receives the signal, either effectively or actually delayed, and transmits the delayed return signal back to the radar via a transmit (Tx) antenna. In some examples, radar 504 may transmit an FM (discontinuous wave) signal as a pulse waveform in some cases. In other examples, radar 504 may transmit an FMCW signal. Between LNA 506 and PA 508 is a delay element 510. The delay element 510 may cause the received FM signal to be transmitted back to radar 504 with an effective delay (e.g., a frequency drift or offset representing the desired delay) or an actual delay. Figure 5 In the examples (and all other transponder examples disclosed herein), the transponder may be located at or near a specific point of interest (e.g., the tip of a stylus) within the object of interest, where precise determination of the object's position or movement is paramount. The Tx and Rx antennas may be separate electrodes located at or near the specific point of interest, and in other examples, the Tx and Rx antennas may share an electrode located at or near the specific point of interest. At radar 504, the frequency difference between the delayed FM return signal received from the object of interest 502 and the output FM signal can be measured. Because the slope of the FM signal is known, the frequency difference and slope can be used to calculate the total delay, and based on this total delay, the distance from radar 504 to the object of interest 502 can be determined.

[0038] Figure 6 An example of a radar-based object tracking system 600 according to this disclosure is shown, comprising an object of interest 602 (e.g., a stylus) and multiple radars 604, the object of interest including a transponder with a delay element 610 capable of creating an effective delay. Figure 6In the example, the transponder also includes an LNA 606 that receives an FMCW signal from one of the radars in radar 604 via an Rx antenna, and a PA 608 that receives a frequency-shifted signal from a delay element 610 and transmits a delayed return signal back to the radar via a Tx antenna. Between the LNA 606 and PA 608 is the delay element 610. The delay element 610 may utilize two PLLs or frequency sources 612, 614 at different frequencies, where the frequency difference is equal to the desired frequency drift or offset representing the desired delay. A mixer 616 may use frequency source 612 to down-convert the radar signal received at the LNA 606 to an intermediate frequency (IF), and an IF bandpass filter (BPF) 620 may filter the down-converted IF signal. This IF signal may be up-converted using mixer 618 and frequency source 614, filtered by the Tx BPF 622, and transmitted back to radar 604 as a delayed return signal via PA 608. The delay element 610 can thus cause the received FMCW signal to be transmitted back to radar 604 with a frequency offset representing the desired delay. At radar 604, the frequency difference between the delayed FMCW signal received from the object of interest 602 and the output FMCW signal can be measured. In the example using FMCW, since the slope of the FMCW signal is known, the frequency difference and the slope can be used to calculate the total delay, and the distance from radar 604 to the object of interest 602 can be determined based on this total delay.

[0039] In one example, a 60 GHz radar can transmit an FMCW signal with a slope of 200 MHz / µsec, and a delay associated with a distance of 10 m is expected. The round-trip time can be calculated as (10 m * 2) / 3e8 = 67 ns. For an FMCW signal slope of -200 MHz / µsec, the beat frequency at a distance of 10 m is 200 MHz / µsec * 67 nsec = 13.4 MHz. If an IF of 15 GHz is desired, frequency source 616 can generate a frequency of 45 GHz to downconvert the received signal, and frequency source 614 can generate a frequency of 45 GHz - 0.0134 GHz = 44.9866 GHz to upconvert the IF signal with a carrier drift of -13.4 MHz, effectively delaying the FMCW signal by 67 ns. Therefore, the frequency of the return signal transmitted back to the radar will be 60 GHz - 0.0134 GHz = 59.9866 GHz.

[0040] Figure 7 An example of a radar-based object tracking system 700 according to this disclosure is shown, comprising an object of interest 702 (e.g., a stylus) and multiple radars 704, the object of interest including a transponder with a delay element 710 capable of creating an actual delay. (As defined herein, the term "transponder" includes "repeater".) Figure 7 In this example, the transponder also includes an LNA 706 that receives FM signals from one of the radars in radar 704 via an Rx antenna, and a PA 708 that receives the signal, which is actually delayed, and transmits the delayed return signal back to the radar via a Tx antenna. Between the LNA 706 and PA 708 is a delay element 710, which in this example can be the actual delay created by the electrical length of the cable (although in other examples, the actual delay can be created by elements other than the electrical length of the cable, such as an mmWave delay element). The electrical length of the cable can cause the received FM signal to be transmitted back to radar 704 with the desired delay. In some examples, a cable electrical length sufficient to produce a sufficient delay can be used to distinguish the desired return signal from the undesired reflection under all expected conditions. In some examples, this cable electrical length can be from 10 meters to 50 meters. In some examples, for frequencies below 6 GHz, a ceramic coaxial cable element with a dielectric constant of up to 9000 at a length of a few centimeters can introduce an electrical delay of several meters. In another example, for frequencies below 6 GHz, a ceramic coaxial element with a dielectric constant of up to 9000 over a physical length of one centimeter can introduce an electrical delay of approximately 95 cm. At radar 704, the frequency difference between the delayed FM signal received from the object of interest 702 and the output FM signal can be measured. Because the slope of the FM signal is known, the frequency difference and the slope can be used to calculate the total delay, and based on this total delay, the distance from radar 704 to the object of interest 702 can be determined.

[0041] In one example, a 60 GHz radar can transmit an FMCW signal with a slope of 200 MHz / µsec and expects a delay associated with a distance of 10 m. The round-trip time can be calculated as (10 m * 2) / 3e8 = 67 ns. For an FMCW signal slope of 200 MHz / µsec, the beat frequency at a distance of 10 m is 200 MHz / µsec * 67 ns = 13.4 MHz. Therefore, a 20 m cable can be applied to the FMCW signal received at the object of interest, effectively delaying the FMCW signal by 67 ns. The radar will then interpret this delay as a beat frequency wavelength of 13.4 MHz.

[0042] Figure 8 An example of a radar-based object tracking system 800 according to this disclosure is shown, comprising an object of interest 802 (e.g., a stylus) and multiple radars 804, the object of interest including a transponder with a delay element 810 capable of creating an actual delay. Figure 8In this example, the transponder also includes an LNA 806 that receives FM signals from one of the radars in radar 804 via an Rx antenna, and a PA 808 that receives a signal from the LNA that is actually delayed and transmits the delayed return signal back to the radar via a Tx antenna. Between the LNA 806 and PA 808 is a delay element 810, which in this example is a digital delay 812. An ADC 814 can be used to convert the received signals from the LNA 806 into digital signals, which can then be delayed in the digital delay 812. In some examples, the ADC 814 may include a full RF chain from the output of the LNA 804 to the digital input of the digital delay 812. In some examples, the ADC 814 may be implemented as a single element or as part of or a combination of heterodyne, superheterodyne, or zero-IF (0 IF) architectures. In some examples, the digital delay 812 may be buffered digital logic, a lookup table, etc. The digital delay 812 can be converted back to an analog signal using a DAC 816, causing the received FM signal to be transmitted back to radar 804 with the desired actual delay. In some examples, DAC 816 may comprise a full RF chain from the digital output of digital delay 812 to the analog input of PA 808. In some examples, DAC 816 may be implemented as a single element or as part of or a combination of heterodyne, superheterodyne, or zero-IF architectures. At radar 804, the frequency difference between the delayed FM return signal received from object of interest 802 and the output FM signal can be measured. Because the slope of the FM signal is known, the frequency difference and the slope can be used to calculate the total delay, and the distance from radar 804 to object of interest 802 can be determined based on this total delay.

[0043] In one example, a 60 GHz radar can transmit an FMCW signal with a slope of 200 MHz / µsec and expects a delay associated with a distance of 10 m. The round-trip time can be calculated as (10 m * 2) / 3e8 = 67 ns. Assuming a digital sampling rate of 5 GHz (or 5 gigabits per second (GSp)), a digital delay of 67 ns * (1 / 5 GHz) ≈ 333 samples can be applied. Therefore, a digital delay of 333 samples can be applied to the FMCW signal received at the object of interest, delaying the FMCW signal by 67 ns. For an FMCW signal slope of 200 MHz / µsec, the beat frequency at a distance of 10 m is 200 MHz / µsec * 67 nsec = 13.4 MHz. Therefore, the radar will interpret the delay as a beat frequency wavelength with a frequency of 13.4 MHz.

[0044] Figure 9An example of a radar-based object tracking system 900 according to this disclosure is shown, comprising an object of interest 902 (e.g., a stylus) and multiple radars 904, the object of interest including a transponder having a delay element 910 capable of creating a delay. Figure 9 In this example, the transponder also includes an LNA 906 that receives FM signals from one of the radars 904 via an Rx antenna, and a PA 908 that receives a delayed signal from the LNA and transmits the delayed return signal back to the radar via a Tx antenna. Between the LNA 906 and PA 908 is a delay element 910, which in this example may include the electrical length of a cable or a digital delay applied to the signal received at the object of interest in IF as discussed above (generally represented by delay block 912). A mixer 914 and a frequency source 916 can be used to downconvert the received RF signal to IF, and the downconverted signal can be filtered using an IF BPF 918. In some examples, the IF BPF 918 may induce the desired delay and eliminate the need for a dedicated delay block 912. In other examples requiring delay block 912, after the IF signal is delayed at 912, mixer 922 and frequency source 916 can upconvert the IF signal to an RF signal, which can be filtered by Tx BPF 920 before being transmitted back to radar 904 with the desired delay using PA 908. At radar 904, the frequency difference between the delayed FM signal received from object of interest 902 and the output FM signal can be measured. Because the slope of the FM signal is known, the frequency difference and slope can be used to calculate the total delay, and the distance from radar 904 to object of interest 902 can be determined based on this total delay.

[0045] In some of the examples presented above, the delay element can be configurable based on the environment. For example, one or more radars can detect the distance to walls and other surrounding objects to determine the size of the environment. In some examples, when pairing an object of interest with a device, each object of interest can receive programming information that allows it to operate with a specific effective delay adapted to the detected environment.

[0046] As described above, in some examples of this disclosure, multiple radars can be used to detect the distance between these radars and the object of interest. To enable multiple radars to communicate with the object of interest, in some examples, (e.g., by...) Figure 2 The radar controller 206 in the device controls each radar in the device to transmit, receive, and measure R1, R2, and R3 at different times. In some examples, instead of operating sequentially, each radar in the device can transmit and receive orthogonal signals, and the circuitry within the object of interest can be configured to sequentially receive, process, and transmit those orthogonal signals, allowing multiple radars to communicate with the object of interest simultaneously.

[0047] As described above, in some examples of this disclosure, multiple objects of interest (OIEs) can be detected by radar in a device to achieve cooperative activity. To enable communication between the multiple OIEs and the device, in some examples, the delay element in each OIE can be programmed to have a unique effective delay. For example, a first OIE might generate an effective delay of 100 m, and a second OIE might generate an effective delay of 200 m. In some examples, when pairing an OIE with the device, each OIE can receive programming information into the transponder control logic, such that each OIE can operate with its own unique effective delay compared to other OIEs paired with that device. In the examples above, the frequency source can be programmed to operate at different frequencies, or the digital delay can be programmed to generate different effective delays. The radar can then search for those frequencies transmitted back from the multiple OIEs without needing to sequence the radar's operation.

[0048] Figure 10 A process 1000 for high-precision object tracking according to an example of this disclosure is illustrated. At 1002, multiple radars at the device can transmit FM signals. In some examples, at 1004, the multiple radars can optionally be subjected to sequential control to adjust the timing of the transmitted FM signals. At 1006, one or more objects of interest can receive the FM signals. At 1008, a delay element can be used to delay the received FM signals, which can effectively or practically delay the received FM signals. In some examples, at 1010, the objects of interest can optionally receive delay information so that each object of interest can generate a unique delay. At 1012, a delayed FM return signal can be transmitted from the object of interest. At 1014, the multiple radars can receive the delayed FM return signal. At 1016, the device can use the delayed FM return signal received at the multiple radars to distinguish the signal from unwanted reflections and extract multiple ranges of the object of interest to each of the multiple radars. At 1018, these ranges can be combined in triangulation or other processing to calculate 2D or 3D object tracking information, such as the location of an object of interest in 2D or 3D.

[0049] Figure 11 An example of a radar-based object tracking system 1100 according to this disclosure is shown, comprising an object of interest 1102 (e.g., a stylus), the object of interest including a transponder 1110 capable of receiving a predefined transmission signal from a radar 1104 and transmitting a unique return signal. Figure 11In the example, object of interest 1102 includes amplifier 1106, which receives a predefined amplified signal from one of the radars in radar 804 via an Rx antenna, and this predefined amplified signal is amplified at amplifier 1106 and then converted into a digital signal at ADC 1114. In some examples, ADC 1114 may be implemented as a single element or as part of or a combination of heterodyne, superheterodyne, or zero-IF architectures. In some examples, ADC 1114 may include a full RF chain from amplifier 1106 to the digital input of receive matched filter 1112. Transponder 1110 then attempts to match the received predefined signal with a known predefined signal using receive matched filter 1112. If a match is found, matched filter 1112 triggers transmit signal generator 1118 to generate a unique return signal, which is then converted into an analog signal in DAC 1116 and then transmitted back to radar 1104 via PA 1108. In some examples, the transmit signal generator 1118 generates a unique return signal based on certain parameters stored in a memory (not shown), and in other examples, the transmit signal generator retrieves a unique return signal stored in a memory (not shown). In some examples, the DAC 1116 may include a full RF chain from the digital output of the transmit signal generator 1118 to the analog input of the PA 1108. In some examples, the DAC 1116 may be implemented as a single element or as part of or a combination of heterodyne, superheterodyne, or zero-IF architectures.

[0050] Radar 1104 then attempts to match the received unique return signal with a known, stored set of return signals using a matching filter. If a match is found, radar 1104 can perform range compression processing. In some examples, range compression processing can determine the distance between the object of interest and the radar based on the delay difference between the transmission time of a predefined transmitted signal and the reception time of the unique return signal. Note that the predefined transmitted signal generated by the radar and the unique return signal received by the radar can be different signals (with the lowest possible correlation between them), because the predefined transmitted signal only needs to be recognized by the transponder so that the unique return signal can be sent back to the radar. In some examples, the predefined transmitted signal and the unique return signal can be linear frequency modulation (LFM) signals with different frequency slopes or different carrier frequencies (i.e., chirps). In some examples, the predefined transmitted signal and the unique return signal can be orthogonal signals, such that when the radar receives the unique return signal and the sum of all echoes from the environment (cluttered echoes), the correlation performed at the radar will produce only a single meaningful correlation.

[0051] Figure 12A process 1200 for high-precision object tracking according to an example of this disclosure is illustrated. At 1202, each of a plurality of radars at the device may transmit a unique predefined transmission signal. In some examples, at 1204, the plurality of radars may optionally be subjected to sequential control to adjust the timing of the transmitted unique predefined transmission signals. At 1206, one or more objects of interest may receive the unique predefined transmission signal. At 1208, the received unique predefined transmission signal may be matched at the object of interest, and if a match is found, a unique return signal may be generated. In some examples, at 1210, the object of interest may optionally receive return signal information such that each object of interest is able to generate a unique return signal. At 1212, a unique return signal may be transmitted from the object of interest. At 1214, the plurality of radars may receive the unique return signal. At 1216, the received unique return signals may be matched at the radars, and if a match is found, the range or distance between the object of interest and the radars may be determined. At 1218, the range of multiple radars can be combined in triangulation or other processing to calculate 2D or 3D object tracking information, such as the position of the object of interest in 2D or 3D.

[0052] The radar-based object tracking systems described above offer various advantages. For example, unlike camera-based object tracking systems, radar-based systems are unaffected by environmental conditions such as strong light, and unlike cameras, mmWave frequencies such as 60 GHz are largely unaffected when passing through materials such as plastics and some metals (i.e., experiencing minimal signal attenuation). This allows the radar transponder to be concealed within the object of interest (e.g., hidden within a stylus) without the need for windows or glass. Additionally, cameras have limited field of view, relatively high power, and large size, and can present privacy concerns. Furthermore, unlike conventional mmWave frequency radar systems, adding a transponder with a delay element to the object of interest allows the radar system to separate and distinguish desired return signals from unwanted reflections, leading to more accurate range determination, more accurate triangulation, and ultimately, more accurate object tracking. The returned signal can also be amplified without amplifying noise from unwanted reflections. Amplification can be useful because the amplitude of the received signal may be relatively small due to attenuation.

[0053] Therefore, according to the foregoing, some examples of this disclosure relate to a transponder for generating a predetermined delay of a first signal received at an object of interest in a radar-based object tracking system. The transponder includes: a receiving amplifier configured to receive the first signal transmitted from a first radar; a delay element configured to delay the received first signal by a predetermined delay; and a transmitting amplifier configured to transmit the delayed first signal back to the first radar. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the first signal is a frequency-modulated continuous wave (FMCW) signal. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the delay element includes a downconverter and an upconverter configured to operate with a frequency difference that is a function of the predetermined delay. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the downconverter includes a first mixer and a first frequency source, and the upconverter includes a second mixer and a second frequency source; and the first frequency source and the second frequency source operate with the frequency difference. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the delay element includes: a downconverter configured to downconvert a received first signal to an intermediate frequency (IF) using a first frequency source; a delay device for delaying the downconverted first signal at the IF by the predetermined delay; and an upconverter configured to upconvert the delayed first signal using the first frequency source. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the delay device includes the electrical length of a cable. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the delay device includes a digital delay. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the delay element includes a digital delay configured to generate the predetermined delay. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the transponder also includes transponder control logic configured to receive unique delay information and program the delay element to change the predetermined delay. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the delay element includes the electrical length of a cable configured to generate the predetermined delay.

[0054] Some examples of this disclosure relate to a method for generating a predetermined delay of a first signal received at an object of interest in a radar-based object tracking system. The method includes receiving the first signal transmitted from a first radar; delaying the received first signal by a predetermined delay; and transmitting the delayed first signal back to the first radar. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the first signal is a frequency-modulated continuous wave (FMCW) signal. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the method further includes down-converting and up-converting the received first signal with a frequency difference that is a function of the predetermined delay. In addition to one or more of the examples disclosed above, or alternatively, in some examples, down-conversion includes mixing the received first signal with a first frequency source; up-conversion includes mixing the down-converted first signal with a second frequency source; and the first frequency source and the second frequency source operate with the frequency difference. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the method further includes down-converting a received first signal to an intermediate frequency (IF) using a first frequency source; delaying the down-converted first signal at the IF by a predetermined delay; and up-converting the delayed first signal using the first frequency source. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the method further includes delaying the down-converted first signal at the IF by the predetermined delay using the electrical length of a cable. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the method further includes delaying the down-converted first signal at the IF by the predetermined delay using a digital delay configured to generate the predetermined delay. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the method further includes delaying the received first signal using a digital delay configured to generate the predetermined delay. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the method further includes receiving unique delay information and changing the predetermined delay. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the method also includes using the electrical length of a cable configured to generate the predetermined delay to delay the received first signal.

[0055] Some examples of this disclosure relate to a radar-based object tracking system for detecting an object of interest. The system includes an apparatus comprising a first radar configured to transmit a first frequency modulation (FM) signal; and an object of interest configured to receive the first FM signal from the first radar, generate a valid predetermined delay in the received first FM signal, and transmit the delayed first FM signal; wherein the first radar is further configured to receive the delayed first FM signal from the object of interest; and wherein the apparatus is configured to distinguish the delayed first FM signal from a reflection of the first FM signal transmitted from the first radar, and use the delayed first FM signal to determine the distance from the apparatus to the object of interest. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the object of interest is further configured to generate the delay by down-converting and up-converting the received first FM signal by a frequency difference that is a function of the predetermined delay. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the object of interest is further configured to generate the delay by down-converting a received first FM signal to an intermediate frequency (IF) using a first frequency source; delaying the down-converted first FM signal at the IF by the predetermined delay; and up-converting the delayed first FM signal using the first frequency source. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the object of interest is further configured to delay the down-converted first FM signal at the IF by the predetermined delay using the electrical length of a cable. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the object of interest is further configured to delay the down-converted first FM signal at the IF by the predetermined delay using a digital delay configured to generate the predetermined delay.

[0056] Some examples of this disclosure relate to a transponder for generating a return signal from an object of interest in a radar-based object tracking system. The transponder includes: a receive amplifier configured to receive a first predefined signal; a matching filter configured to match the received first predefined signal with a known predefined signal; a transmit signal generator configured to generate a unique return signal when a match with the received first predefined signal is found; and a transmit amplifier configured to transmit the unique return signal. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the transmit signal generator is further configured to generate the unique return signal based on stored parameters. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the transmit signal generator is further configured to generate the unique return signal based on stored return signals. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the first predefined signal and the unique return signal are orthogonal. In addition to one or more of the examples disclosed above, or alternatively, in some examples, the first predefined signal and the only return signal are linear frequency modulation (LFM) signals.

[0057] Although examples of this disclosure have been fully described with reference to the accompanying drawings, it should be noted that various changes and modifications will become apparent to those skilled in the art. It should be understood that such changes and modifications are considered to be included within the scope of the examples of this disclosure as defined by the appended claims.

Claims

1. A transponder for generating a predetermined delay of a first signal received at an object of interest in a radar-based object tracking system, the transponder comprising: Receiving antenna; A receiving amplifier configured to receive the first signal transmitted from the first radar via the receiving antenna; A delay element configured to delay the received first signal by a predetermined delay; A downconverter configured to mix a received first signal with a first frequency source operating at a frequency difference, wherein the frequency difference is a function of the predetermined delay; An upconverter configured to mix a downconverted first signal with a second frequency source operating at the frequency difference; Transmitting antenna; as well as A transmit amplifier configured to transmit a delayed first signal back to the first radar via the transmit antenna.

2. The transponder according to claim 1, wherein the first signal is a frequency modulated continuous wave (FMCW) signal.

3. The transponder according to claim 1, wherein the downconverter includes a first mixer and the upconverter includes a second mixer, the downconversion including mixing the received first signal with the first frequency source using the first mixer, and the upconversion including mixing the downconverted first signal with the second frequency source using the second mixer.

4. The transponder according to claim 1, wherein: The downconverter is configured to use the first frequency source to downconvert the received first signal to an intermediate frequency; The delay element includes a delay device, which is used to delay the first signal after down-conversion at the intermediate frequency by a predetermined delay; as well as The upconverter is configured to upconvert the delayed first signal using the first frequency source.

5. The transponder of claim 4, wherein the delay device comprises the electrical length of the cable.

6. The transponder of claim 4, wherein the delay device comprises a digital delay.

7. The transponder of claim 1, wherein the delay element comprises a digital delay configured to generate the predetermined delay.

8. The transponder of claim 1, further comprising transponder control logic configured to receive unique delay information and program the delay element to change the predetermined delay.

9. The transponder of claim 1, wherein the delay element comprises an electrical length of cable configured to generate the predetermined delay.

10. The transponder according to claim 1, further comprising: A matching filter, configured to match the received first signal with a known predefined signal; as well as A transmit signal generator is configured to generate a unique return signal when a match with a received first signal is found based on stored parameters.

11. The transponder according to claim 1, further comprising: A matching filter, configured to match the received first signal with a known predefined signal; as well as A transmit signal generator is configured to generate a unique return signal when a match is found between the stored return signal and the received first signal.

12. The transponder of claim 11, wherein the first signal and the unique return signal are orthogonal.

13. The transponder of claim 11, wherein the first signal and the unique return signal are linear frequency modulated (LFM) signals.

14. A method for generating a predetermined delay of a first signal received at an object of interest in a radar-based object tracking system, the method comprising: Receive the first signal transmitted from the first radar; The received first signal is delayed by a predetermined time; The received first signal is down-converted and then up-converted using the frequency difference as a function of the predetermined delay. as well as The delayed first signal is transmitted back to the first radar, wherein: Down-conversion includes mixing the received first signal with a first frequency source; Upconversion includes mixing the downconverted first signal with a second frequency source; and The first frequency source and the second frequency source operate with the frequency difference.

15. The method of claim 14, wherein the first signal is a frequency modulated continuous wave (FMCW) signal.

16. The method of claim 14, further comprising: The received first signal is down-converted to an intermediate frequency using a first frequency source; The first signal after down-conversion at the intermediate frequency is delayed by the predetermined delay; as well as The first frequency source is used to upconvert the delayed first signal.

17. The method of claim 16, further comprising using the electrical length of the cable to delay the first signal after downconversion at the intermediate frequency by the predetermined delay.

18. The method of claim 16, further comprising using a digital delay configured to generate the predetermined delay to delay the first signal after downconversion at the intermediate frequency by the predetermined delay.

19. The method of claim 14, further comprising using a digital delay configured to generate the predetermined delay to delay the received first signal.

20. The method of claim 14, further comprising receiving unique delay information and changing the predetermined delay.

21. The method of claim 14, further comprising using the electrical length of a cable configured to generate the predetermined delay to delay the received first signal.

22. A radar-based object tracking system for detecting a stylus with a tip, the system comprising: A computing device, the computing device including a first radar configured to transmit a first frequency modulated (FM) signal; as well as The stylus is configured to receive a first FM signal from the first radar, generate a valid predetermined delay in the received first FM signal, and transmit the delayed first FM signal. The first radar is further configured to receive the delayed first FM signal from the stylus; and The computing device is configured to distinguish the delayed first FM signal from a reflection of the first FM signal emitted from the first radar, and to use the delayed first FM signal to determine the distance from the computing device to the tip of the stylus.

23. The system of claim 22, wherein the stylus is further configured to generate the effective predetermined delay by down-converting and up-converting the received first FM signal with a frequency difference as a function of the effective predetermined delay.

24. The system of claim 22, wherein the stylus is further configured to: The effective predetermined delay is generated by downconverting the received first FM signal to an intermediate frequency using a first frequency source; The first FM signal after down-conversion at the intermediate frequency is delayed by the effective predetermined delay; as well as The first frequency source is used to upconvert the delayed first FM signal.

25. The system of claim 24, wherein the stylus is further configured to use the electrical length of the cable to delay the first FM signal after downconversion at the intermediate frequency by the effective predetermined delay.

26. The system of claim 24, wherein the stylus is further configured to use a digital delay configured to generate the effective predetermined delay in the first FM signal after the intermediate frequency is down-converted to the intermediate frequency to delay the effective predetermined delay.

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