PATENT DOCUMENT

Publication Number: US-11782151-B2
Application Number: US-202117332221-A
Country: US
Kind Code: B2

Title: Electronic devices with non-static object detection

Abstract:
An electronic device may include a voltage standing wave ratio (VSWR) sensor disposed along a radio-frequency transmission line between a signal generator and an antenna. The VSWR sensor may gather VSWR measurements from radio-frequency signals transmitted by the signal generator over the transmission line. Control circuitry may identify a variation in the VSWR measurements over time and may compare the variation to a threshold value to determine whether an external object in the vicinity of the antenna is animate or inanimate. The control circuitry may reduce the maximum transmit power level of the antenna when the external object is animate and may maintain or increase the maximum transmit power level when the external object is inanimate. This may serve to maximize the wireless performance of the electronic device while also ensuring that the device complies with regulatory limits on radio-frequency energy exposure.

Claims:
What is claimed is: 
     
       1. An electronic device operable in an environment that includes an external object, the electronic device comprising:
 an antenna; 
 a transmitter coupled to the antenna over a radio-frequency transmission line path, the transmitter being configured to transmit radio-frequency signals to another electronic device using the antenna and the radio-frequency transmission line path; 
 a voltage standing wave ratio (VSWR) sensor disposed on the radio-frequency transmission line path, the VSWR sensor being configured to perform VSWR measurements using the radio-frequency signals transmitted by the transmitter; 
 radar circuitry communicably coupled to the antenna and configured to detect a range to the external object based on a radar signal transmitted by the antenna and received by the radar circuitry; and 
 one or more processors configured to calibrate the detected range to compensate for a path loss associated with a removable case detected based on the VSWR measurements. 
 
     
     
       2. The electronic device of  claim 1 , wherein the one or more processors being further configured to reduce a maximum transmit power level of the antenna based on the VSWR measurements. 
     
     
       3. The electronic device of  claim 2 , the one or more processors being further configured to increase the maximum transmit power level of the antenna based on the VSWR measurements. 
     
     
       4. The electronic device of  claim 1 , the one or more processors being further configured to detect the removable case based on a magnitude of the VSWR measurements. 
     
     
       5. The electronic device of  claim 4 , wherein the VSWR sensor is configured to perform a background VSWR measurement in response to the one or more processors determining that the external object is the removable case, the one or more processors being further configured to background-cancel subsequent VSWR measurements by the VSWR sensor based on the background VSWR measurement. 
     
     
       6. The electronic device of  claim 1 , the one or more processors being further configured to identify a range between the external object and the antenna based on a variation in the VSWR measurements. 
     
     
       7. The electronic device of  claim 1 , wherein the radar circuitry comprises a sequential signal generator and the sequential signal generator is configured to generate the radar signal. 
     
     
       8. The electronic device of  claim 1 , the one or more processors being further configured to:
 compare a variation in the VSWR measurements to a threshold value; 
 determine that the external object is animate when the identified variation in the VSWR measurements exceeds the threshold value; and 
 determine that the external object is inanimate when the identified variation in the VSWR measurements is less than the threshold value. 
 
     
     
       9. A method of operating an electronic device, the method comprising:
 with a signal generator, transmitting radio-frequency signals during a sampling period over a radio-frequency transmission line communicably coupled to an antenna; 
 with a voltage standing wave ratio (VSWR) sensor disposed along the radio-frequency transmission line, performing VSWR measurements from the radio-frequency signals transmitted over the radio-frequency transmission line during the sampling period; 
 with one or more processors, detecting a removable case on the electronic device based on the VSWR measurements; 
 with radar circuitry, transmitting and receiving a radar signal using the antenna; 
 with one or more processors, detecting a range to an external object based on the transmitted and received radar signal; and 
 with the one or more processors, calibrating the detected range to compensate for a path loss associated with the removable case detected based on the VSWR measurements. 
 
     
     
       10. The method of  claim 9 , wherein performing the VSWR measurements comprises performing at least two VSWR measurements that are separated by at least 10 ms. 
     
     
       11. The method of  claim 9 , wherein the sampling period comprises a rolling sampling period. 
     
     
       12. An electronic device comprising:
 an antenna; 
 a transmitter coupled to the antenna over a radio-frequency transmission line path, the transmitter being configured to transmit radio-frequency signals using the antenna and the radio-frequency transmission line path; 
 a voltage standing wave ratio (VSWR) sensor disposed on the radio-frequency transmission line path, the VSWR sensor being configured to gather VSWR values from the radio-frequency signals transmitted by the antenna; and 
 one or more processors configured to
 detect a range to an external object based on the radio-frequency signals transmitted by the antenna and a reflected version of the radio-frequency signals transmitted by the antenna, and 
 calibrate the detected range based on a removable case detected, by the one or more processors, based on the VSWR values. 
 
 
     
     
       13. The electronic device of  claim 12 , the one or more processors being further configured to perform removable case detection when a variation in the VSWR values is less than a threshold value. 
     
     
       14. The electronic device of  claim 13 , wherein the VSWR values are gathered over a sampling period, the one or more processors being further configured to identify the variation in the VSWR values by subtracting a minimum of the VSWR values gathered over the sampling period from a maximum of the VSWR values gathered over the sampling period.

Description:
FIELD 
     This disclosure relates generally to electronic devices and, more particularly, to electronic devices with wireless circuitry. 
     BACKGROUND 
     Electronic devices are often provided with wireless capabilities. An electronic device with wireless capabilities has wireless circuitry that includes one or more antennas. The wireless circuitry is sometimes used to perform spatial ranging operations in which radio-frequency signals are used to estimate a distance between the electronic device and external objects. 
     It can be challenging to provide wireless circuitry that accurately estimates this distance. For example, the wireless circuitry will often exhibit a blind spot near the device within which the wireless circuitry is unable to accurately detect the presence of external objects. In addition, it can be difficult for the wireless circuitry to distinguish between animate and inanimate external objects. 
     SUMMARY 
     An electronic device may include wireless circuitry controlled by one or more processors. The wireless circuitry may include an antenna coupled to a signal generator over a radio-frequency transmission line. A voltage standing wave ratio (VSWR) sensor may be disposed along the radio-frequency transmission line. The signal generator may transmit radio-frequency signals over the radio-frequency transmission line. The radio-frequency signals may be communications signals, radar signals, or dedicated test signals. The VSWR sensor may gather VSWR measurements from the transmitted radio-frequency signals during a sampling period. 
     The one or more processors may identify a variation in the VSWR measurements gathered over the sampling period as a function of time. The one or more processors may compare the variation to a threshold value to determine whether an external object in the vicinity of the antenna is animate or inanimate. The one or more processors may identify that the external object is animate when the variation exceeds the threshold value. The one or more processors may identify that the external object is inanimate when the variation is less than the threshold value. The one or more processors may reduce a maximum transmit power level of the antenna and may optionally identify a range to the external object in response to identifying that the external object is animate. The one or more processors may maintain or increase the maximum transmit power level and may optionally perform removable case detection in response to identifying that the external object is inanimate. This may serve to maximize the wireless performance of the electronic device while also ensuring that the device complies with regulatory limits on radio-frequency energy exposure. 
     An aspect of the disclosure provides an electronic device operable in an environment that includes an external object. The electronic device can include an antenna. The electronic device can include a voltage standing wave ratio (VSWR) sensor communicably coupled to the antenna. The VSWR sensor can be configured to perform VSWR measurements from radio-frequency signals transmitted by the antenna. The electronic device can include one or more processors. The one or more processors can be configured to identify a variation in the VSWR measurements over time. The one or more processors can be configured to determine whether the external object is animate or inanimate based on the identified variation in the VSWR measurements. 
     An aspect of the disclosure provides a method of operating an electronic device to perform animate object detection on an object external to the electronic device. The method can include with a signal generator, transmitting radio-frequency signals during a sampling period over a radio-frequency transmission line communicably coupled to an antenna. The method can include with a voltage standing wave ratio (VSWR) sensor disposed along the radio-frequency transmission line, performing VSWR measurements from the radio-frequency signals transmitted over the radio-frequency transmission line during the sampling period. The method can include with one or more processors, identifying a variation in the VSWR measurements as a function of time within the sampling period. The method can include with the one or more processors, identifying that the object is animate when the identified variation exceeds a threshold value. The method can include with the one or more processors, identifying that the object is inanimate when the identified variation is less than the threshold value. 
     An aspect of the disclosure provides an electronic device. The electronic device can include an antenna. The electronic device can include a voltage standing wave ratio (VSWR) sensor communicably coupled to the antenna. The VSWR sensor can be configured to measure VSWR values from radio-frequency signals transmitted by the antenna. The electronic device can include one or more processors. The one or more processors can be configured to identify a variation in the VSWR values over time. The one or more processors can be configured to decrease a maximum transmit power level of the antenna when the identified variation exceeds a threshold value. The one or more processors can be configured to maintain or increase the maximum transmit power level of the antenna when the identified variation is less than the threshold value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a functional block diagram of an illustrative electronic device having a transmit antenna that is used to perform animate external object detection in accordance with some embodiments. 
         FIG.  2    is a plot of reflection coefficient as a function of frequency that may be produced by an illustrative voltage standing wave ratio (VSWR) sensor in response to the absence and presence of an external object adjacent to a transmit antenna in accordance with some embodiments. 
         FIG.  3    is a circuit diagram of an illustrative VSWR sensor having a directional coupler for performing animate external object detection using a transmit antenna in accordance with some embodiments. 
         FIG.  4    is a plot showing how the reflection coefficient measured by an illustrative VSWR sensor may vary at different times when an animate object is present adjacent to a transmit antenna in accordance with some embodiments. 
         FIG.  5    is a plot showing how the reflection coefficient measured by an illustrative VSWR sensor may vary as a function of time in the presence of an inanimate external object, in the presence of an animate external object, and in the presence of no external object adjacent to a transmit antenna in accordance with some embodiments. 
         FIG.  6    is a plot showing how the return loss measured by an illustrative VSWR sensor may vary when the electronic device is provided with different types of removable cases in accordance with some embodiments. 
         FIG.  7    is a flow chart of illustrative operations involved in gathering VSWR measurements with a VSWR sensor for use in performing animate object detection in accordance with some embodiments. 
         FIG.  8    is a flow chart of illustrative operations involved in performing animate object detection based on variations in VSWR measurements gathered by a VSWR sensor in accordance with some embodiments. 
         FIG.  9    is a plot showing how reflection coefficient variation may be correlated to the range between a transmit antenna and an external object in accordance with some embodiments. 
         FIG.  10    shows illustrative timing diagrams for gathering VSWR measurements using a VSWR sensor for performing animate object detection in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic device  10  of  FIG.  1    may be a computing device such as a laptop computer, a desktop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wristwatch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, a wireless internet-connected voice-controlled speaker, a home entertainment device, a remote control device, a gaming controller, a peripheral user input device, a wireless base station or access point, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     As shown in the functional block diagram of  FIG.  1   , device  10  may include components located on or within an electronic device housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, metal alloys, etc.), other suitable materials, or a combination of these materials. In some situations, parts or all of housing  12  may be formed from dielectric or other low-conductivity material (e.g., glass, ceramic, plastic, sapphire, etc.). In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may include control circuitry  14 . Control circuitry  14  may include storage such as storage circuitry  16 . Storage circuitry  16  may include hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid-state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Storage circuitry  16  may include storage that is integrated within device  10  and/or removable storage media. 
     Control circuitry  14  may include processing circuitry such as processing circuitry  18 . Processing circuitry  18  may be used to control the operation of device  10 . Processing circuitry  18  may include on one or more microprocessors, microcontrollers, digital signal processors, host processors, baseband processor integrated circuits, application specific integrated circuits, central processing units (CPUs), etc. Control circuitry  14  may be configured to perform operations in device  10  using hardware (e.g., dedicated hardware or circuitry), firmware, and/or software. Software code for performing operations in device  10  may be stored on storage circuitry  16  (e.g., storage circuitry  16  may include non-transitory (tangible) computer readable storage media that stores the software code). The software code may sometimes be referred to as program instructions, software, data, instructions, or code. Software code stored on storage circuitry  16  may be executed by processing circuitry  18 . 
     Control circuitry  14  may be used to run software on device  10  such as satellite navigation applications, internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, control circuitry  14  may be used in implementing communications protocols. Communications protocols that may be implemented using control circuitry  14  include internet protocols, wireless local area network (WLAN) protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol or other wireless personal area network (WPAN) protocols, IEEE 802.11ad protocols (e.g., ultra-wideband protocols), cellular telephone protocols (e.g., 3G protocols, 4G (LTE) protocols, 5G protocols, etc.), antenna diversity protocols, satellite navigation system protocols (e.g., global positioning system (GPS) protocols, global navigation satellite system (GLONASS) protocols, etc.), antenna-based spatial ranging protocols (e.g., radio detection and ranging (RADAR) protocols or other desired range detection protocols for signals conveyed at millimeter and centimeter wave frequencies), or any other desired communications protocols. Each communications protocol may be associated with a corresponding radio access technology (RAT) that specifies the physical connection methodology used in implementing the protocol. 
     Device  10  may include input-output circuitry  20 . Input-output circuitry  20  may include input-output devices  22 . Input-output devices  22  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  22  may include user interface devices, data port devices, and other input-output components. For example, input-output devices  22  may include touch sensors, displays (e.g., touch-sensitive and/or force-sensitive displays), light-emitting components such as displays without touch sensor capabilities, buttons (mechanical, capacitive, optical, etc.), scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, audio jacks and other audio port components, digital data port devices, motion sensors (accelerometers, gyroscopes, and/or compasses that detect motion), capacitance sensors, temperature sensors, proximity sensors, magnetic sensors, force sensors (e.g., force sensors coupled to a display to detect pressure applied to the display), etc. In some configurations, keyboards, headphones, displays, pointing devices such as trackpads, mice, and joysticks, and other input-output devices may be coupled to device  10  using wired or wireless connections (e.g., some of input-output devices  22  may be peripherals that are coupled to a main processing unit or other portion of device  10  via a wired or wireless link). 
     Input-output circuitry  20  may include wireless circuitry  24  to support wireless communications and/or radio-based spatial ranging operations. Wireless circuitry  24  may include two or more antennas  40 . Wireless circuitry  24  may also include baseband processor circuitry, transceiver circuitry, amplifier circuitry, filter circuitry, switching circuitry, analog-to-digital converter (ADC) circuitry, digital-to-analog converter (DAC) circuitry, radio-frequency transmission lines, and/or any other circuitry for transmitting and/or receiving radio-frequency signals using antennas  40 . 
     Antennas  40  may be formed using any desired antenna structures. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, monopole antennas, dipoles, hybrids of these designs, etc. Filter circuitry, switching circuitry, impedance matching circuitry, and/or other antenna tuning components may be adjusted to adjust the frequency response and wireless performance of antennas  40  over time. 
     Antennas  40  may include one or more transmit (TX) antennas such as transmit antenna  40 TX and one or more receive (RX) antennas such as receive antenna  40 RX. Antennas  40  may include zero, one, or more than one additional antenna used in the transmission and/or reception of radio-frequency signals. Transmit antenna  40 TX may transmit radio-frequency signals such as radio-frequency signals  42  and/or radio-frequency signals  38 . Receive antenna  40 RX may receive radio-frequency signals such as radio-frequency signals  44  and/or radio-frequency signals  38 . Wireless circuitry  24  may use antennas  40  to transmit and/or receive radio-frequency signals  38  to convey wireless communications data between device  10  and external wireless communications equipment  48  (e.g., one or more other devices such as device  10 , a wireless access point or base station, etc.). Wireless communications data may be conveyed by wireless circuitry  24  bidirectionally or unidirectionally. The wireless communications data may, for example, include data that has been encoded into corresponding data packets such as wireless data associated with a telephone call, streaming media content, internet browsing, wireless data associated with software applications running on device  10 , email messages, etc. 
     Wireless circuitry  24  may include communications circuitry  26  (sometimes referred to herein as wireless communications circuitry  26 ) for transmitting and/or receiving wireless communications data using antennas  40 . Communications circuitry  26  may include baseband circuitry (e.g., one or more baseband processors) and one or more radios (e.g., radio-frequency transceivers, modems, etc.) for conveying radio-frequency signals  38  using one or more antennas  40  (e.g., transmit antenna  40 TX, receive antenna  40 RX, and/or other antennas  40 ). 
     Communications circuitry  26  may transmit and/or receive radio-frequency signals  38  within a corresponding frequency band at radio frequencies (sometimes referred to herein as a communications band or simply as a “band”). The frequency bands handled by communications circuitry  26  may include wireless local area network (WLAN) frequency bands (e.g., Wi-Fi® (IEEE 802.11) or other WLAN communications bands) such as a 2.4 GHz WLAN band (e.g., from 2400 to 2480 MHz), a 5 GHz WLAN band (e.g., from 5180 to 5825 MHz), a Wi-Fi® 6E band (e.g., from 5925-7125 MHz), and/or other Wi-Fi® bands (e.g., from 1875-5160 MHz), wireless personal area network (WPAN) frequency bands such as the 2.4 GHz Bluetooth® band or other WPAN communications bands, cellular telephone frequency bands (e.g., bands from about 600 MHz to about 5 GHz, 3G bands, 4G LTE bands, 5G New Radio Frequency Range  1  (FR1) bands below 10 GHz, 5G New Radio Frequency Range  2  (FR2) bands between 20 and 60 GHz, etc.), other centimeter or millimeter wave frequency bands between 10-300 GHz, near-field communications frequency bands (e.g., at 13.56 MHz), satellite navigation frequency bands (e.g., a GPS band from 1565 to 1610 MHz, a Global Navigation Satellite System (GLONASS) band, a BeiDou Navigation Satellite System (BDS) band, etc.), ultra-wideband (UWB) frequency bands that operate under the IEEE 802.15.4 protocol and/or other ultra-wideband communications protocols, communications bands under the family of 3GPP wireless communications standards, communications bands under the IEEE 802.XX family of standards, and/or any other desired frequency bands of interest. 
     Communications circuitry  26  may be coupled to antennas  40  using one or more transmit paths and/or one or more receive paths. Communications circuitry  26  uses the transmit paths to transmit radio-frequency signals  38  and uses the receive paths to receive radio-frequency signals  38 . If desired, communications circuitry  26  may be coupled to transmit antenna  40 TX over a transmit path such as transmit path  34 . Communications circuitry  26  may use transmit path  34  to transmit radio-frequency signals  38  using transmit antenna  40 TX. Transmit path  34  (sometimes referred to herein as transmit chain  34 ) may include one or more signal paths (e.g., radio-frequency transmission lines), amplifier circuitry, filter circuitry, switching circuitry, radio-frequency front end circuitry (e.g., components on a radio-frequency front end module), and/or any other desired paths or circuitry for transmitting radio-frequency signals from communications circuitry  26  to transmit antenna  40 TX. 
     In addition to conveying wireless communications data, wireless circuitry  24  may also use antennas  40  to perform spatial ranging operations. Wireless circuitry  24  may include long range spatial ranging circuitry  28  for performing spatial ranging operations. Long range spatial ranging circuitry  28  may include mixer circuitry, amplifier circuitry, transmitter circuitry (e.g., signal generators, synthesizers, etc.), receiver circuitry, filter circuitry, baseband circuitry, ADC circuitry, DAC circuitry, and/or any other desired components used in performing spatial ranging operations using antennas  40 . Long range spatial ranging circuitry  28  may include, for example, radar circuitry (e.g., frequency modulated continuous wave (FMCW) radar circuitry, OFDM radar circuitry, FSCW radar circuitry, a phase coded radar circuitry, other types of radar circuitry). Antennas  40  may include separate antennas for conveying wireless communications data and radio-frequency signals for spatial ranging or may include one or more antennas  40  that are used to both convey wireless communications data and to perform spatial ranging. Using a single antenna  40  to both convey wireless communications data and perform spatial ranging may, for example, serve to minimize the amount of space occupied in device  10  by antennas  40 . 
     In one embodiment that is described herein as an example, wireless circuitry  24  may use transmit antenna  40 TX to both convey wireless communications data for communications circuitry  26  and perform spatial ranging operations for long ranging spatial ranging circuitry  28 . Long range spatial ranging circuitry  28  may therefore be coupled to transmit antenna  40 TX over transmit path  34 . When performing spatial ranging operations, long range spatial ranging circuitry  28  may use transmit antenna  40 TX to transmit radio-frequency signals  42 . Radio-frequency signals  42  may include one or more signal tones, continuous waves of radio-frequency energy, wideband signals, chirp signals, or any other desired transmit signals (e.g., radar signals) for use in spatial ranging operations. Unlike radio-frequency signals  38 , radio-frequency signals  42  may be free from wireless communications data (e.g., cellular communications data packets, WLAN communications data packets, etc.). Radio-frequency signals  42  may sometimes also be referred to herein as spatial ranging signals  42 , long range spatial ranging signals  42 , or radar signals  42 . Long range spatial ranging circuitry  28  may transmit radio-frequency signals  42  at one or more carrier frequencies in a corresponding radio frequency band such (e.g., a frequency band that includes frequencies greater than around 10 GHz, greater than around 20 GHz, less than 10 GHz, 20-30 GHz, greater than 40 GHz, etc.). 
     Radio-frequency signals  42  may reflect off of objects external to device  10  such as external object  46 . External object  46  may be, for example, the ground, a building, part of a building, a wall, furniture, a ceiling, a person, a body part, an animal, a vehicle, a landscape or geographic feature, an obstacle, external communications equipment such as external wireless communications equipment  48 , another device of the same type as device  10  or a peripheral device such as a gaming controller or remote control, or any other physical object or entity that is external to device  10 . Receive antenna  40 RX may receive reflected radio-frequency signals  44 . Reflected signals  44  may be a reflected version of the transmitted radio-frequency signals  42  that have reflected off of external object  46  and back towards device  10 . 
     Receive antenna  40 RX may be coupled to long range spatial ranging circuitry  28  over receive path  36  (sometimes referred to herein as receive chain  36 ). Long range spatial ranging circuitry  28  may receive reflected signals  44  from receive antenna  40 RX via receive path  36 . Receive path  36  may include one or more signal paths (e.g., radio-frequency transmission lines), amplifier circuitry (e.g., low noise amplifier (LNA) circuitry), filter circuitry, switching circuitry, radio-frequency front end circuitry (e.g., components on a radio-frequency front end module), and/or any other desired paths or circuitry for conveying radio-frequency signals from receive antenna  40 RX to long range spatial ranging circuitry  28 . 
     Control circuitry  14  may process the transmitted radio-frequency signals  42  and the received reflected signals  44  to detect or estimate the range R between device  10  and external object  46 . If desired, control circuitry  14  may also process the transmitted and received signals to identify a two or three-dimensional spatial location (position) of external object  46 , a velocity of external object  46 , and/or an angle of arrival of reflected signals  44 . If desired, a loopback path such as loopback path  50  may be coupled between transmit path  34  and receive path  36 . Loopback path  50  may be used to convey transmit signals on transmit path  34  to receiver circuitry in long range spatial ranging circuitry  28 . As an example, in embodiments where long range spatial ranging circuitry  28  performs spatial ranging using an FMCW scheme, loopback path  50  may be a de-chirp path that conveys chirp signals on transmit path  34  to a de-chirp mixer in long range spatial ranging circuitry  28 . In these embodiments, doppler shifts in continuous wave transmit signals may be detected and processed to identify the velocity of external object  46 , and the time dependent frequency difference between radio-frequency signals  42  and reflected signals  44  may be detected and processed to identify range R and/or the position of external object  46 . Use of continuous wave signals for estimating range R may allow control circuitry  14  to reliably distinguish between external object  46  and other background or slower-moving objects, for example. This example is merely illustrative and, in general, long range spatial ranging circuitry  28  may implement any desired radar or long range spatial ranging scheme. 
     The radio-frequency transmission lines in transmit path  34  and receive path  36  may include coaxial cables, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, transmission lines formed from combinations of transmission lines of these types, etc. Transmission lines in device may be integrated into rigid and/or flexible printed circuit boards if desired. One or more radio-frequency lines may be shared between transmit path  34  and receive path  36  if desired. The components of wireless circuitry  24  may be formed on one or more common substrates or modules (e.g., rigid printed circuit boards, flexible printed circuit boards, integrated circuits, chips, packages, systems-on-chip, etc.). 
     The example of  FIG.  1    is merely illustrative. While control circuitry  14  is shown separately from wireless circuitry  24  in the example of  FIG.  1    for the sake of clarity, wireless circuitry  24  may include processing circuitry that forms a part of processing circuitry  18  and/or storage circuitry that forms a part of storage circuitry  16  of control circuitry  14  (e.g., portions of control circuitry  14  may be implemented on wireless circuitry  24 ). As an example, some or all of the baseband circuitry in wireless circuitry  24  may form a part of control circuitry  14 . In addition, wireless circuitry  24  may include any desired number of antennas  40 . Antennas  40  may include more than one transmit antenna  40 TX, more than one receive antenna  40 RX, and zero, one, or more than one other antenna  40 . Each antenna  40  may be coupled to communications circuitry  26  and/or long range spatial ranging circuitry  28  over dedicated transmit and/or receive paths or over one or more transmit and/or receive paths that are shared between antennas. 
     Long range spatial ranging circuitry  28  need not be coupled to all of the antennas  40  in wireless circuitry  24 . Similarly, communications circuitry  26  need not be coupled to all of the antennas  40  in wireless circuitry  24  (e.g., some antennas  40  may be used to only perform spatial ranging operations without conveying wireless communications data or to only convey wireless communications data without performing spatial ranging). Antennas  40  that are only used to receive signals may be coupled to communications circuitry  26  and/or long range spatial ranging circuitry  28  using one or more receive paths (e.g., receive path  36 ). Antennas  40  that are only used to transmit signals may be coupled to communications circuitry  26  and/or long range spatial ranging circuitry  28  using one or more transmit paths (e.g., transmit path  34 ). One or more antennas  40  may be used to both transmit and receive signals. In these scenarios, the antenna may be coupled to communications circuitry  26  and/or long range spatial ranging circuitry  28  using both a transmit path and a receive path and, if desired, one or more components or signal paths (e.g., radio-frequency transmission lines) may be shared between both the transmit path and the receive path. While described herein as a transmit antenna for the sake of simplicity, transmit antenna  40 TX may also be used in the reception of radio-frequency signals for communications circuitry  26  if desired (e.g., an additional receive path (not shown) may couple transmit antenna  40 TX to communications circuitry  26 ). Similarly, receive antenna  40 RX may also be used in the transmission of radio-frequency signals if desired. While receive antenna  40 RX is only illustrated as providing reflected signals  44  to long range spatial ranging circuitry  28 , receive antenna  40 RX may also provide received radio-frequency signals  38  to communications circuitry  26  (e.g., receive path  36  may also couple receive antenna  40 RX to communications circuitry  26 ). 
     Long range spatial ranging circuitry  28  may be used to accurately identify range R when external object  46  is at relatively far distances from device  10 . However, in practice, long range spatial ranging circuitry  28  exhibits a blind spot to nearby external objects at distances less than threshold range R TH  (e.g., around 1-2 cm) from device  10 . When external object  46  is located within this blind spot (e.g., within threshold range R TH  from transmit antenna  40 TX), long range spatial ranging circuitry  28  may be unable to identify the presence, location, and/or velocity of external object  46  with a satisfactory level of accuracy. External objects  46  within threshold range R TH  of transmit antenna  40 TX may be exposed to relatively high amounts of radio-frequency energy (e.g., from the radio-frequency signals  38  and/or  42  that are transmitted by transmit antenna  40 TX). In scenarios where external object  46  is a body part or person, if care is not taken, this transmitted radio-frequency energy may cause wireless circuitry  24  to exceed regulatory limits or other limits on specific absorption rate (SAR) (e.g., when the transmitted signals are at frequencies below 6 GHz) and/or maximum permissible exposure (MPE) (e.g., when the transmitted signals are at frequencies above 6 GHz). In order to detect the presence of external object  46  within threshold range R TH  from transmit antenna  40 TX, wireless circuitry  24  may include an ultra-short range (USR) object detector such as USR detector  30 . USR detector  30  may serve to detect external object  46  at ultra-short ranges (e.g., at ranges within threshold range R TH  from transmit antenna  40 TX). In other words, USR detector  30  may perform external object detection within the blind spot of long range spatial ranging circuitry  28 . 
     USR detector  30  may include a voltage standing wave ratio (VSWR) sensor (detector) such as VSWR sensor  32 . VSWR sensor  32  may be interposed on transmit path  34 . VSWR sensor  32  may gather VSWR values using transmit antenna  40 TX. The VSWR values may include complex scattering parameter values (S-parameter values) such as reflection coefficient (return loss) values (e.g., S 11  values). The magnitude of the S 11  values (e.g., |S 11 | values) may be indicative of the amount of transmitted radio-frequency energy that is reflected in a reverse direction along transmit path  34  (e.g., in response to the presence of external object  46  at or adjacent to transmit antenna  40 TX). The VSWR values gathered by VSWR sensor  32  may be insensitive to situations where external object  46  is located at distances greater than threshold range R TH  from transmit antenna  40 TX. However, the VSWR values gathered by VSWR sensor  32  may allow control circuitry  14  to identify when external object  46  is located within threshold range R TH  from transmit antenna  40 TX (e.g., within the blind spot of long range spatial ranging circuitry  28 ). 
     In this way, USR detector  30  and long range spatial ranging circuitry  28  may identify the presence of external object  46  and optionally the range R to external object  46 , regardless of whether external object  46  has moved to a position that is relatively close or relatively far from device  10  over time. In addition, USR detector  30  may identify the presence of external object  46  within the blind spot of long range spatial ranging circuitry  28  so that suitable action can be taken to ensure that wireless circuitry  24  continues to satisfy any applicable SAR and/or MPE regulations. By using the same transmit antenna  40 TX to both transmit radio-frequency signals  38 / 42  and measure VSWR, the VSWR measurements will be very closely correlated with the amount of radio-frequency energy absorbed by external object  46  from the transmitted radio-frequency signals  38 / 42 , thereby providing high confidence in the use of USR detector  30  for meeting any applicable SAR and/or MPE regulations (e.g., greater confidence than in scenarios where proximity sensors that are separate from the transmit antenna or transmit chain are used to identify the presence of external objects within threshold range R TH  of device  10 ). 
       FIG.  2    is a plot showing how VSWR measurements made by VSWR sensor  32  may change due to the presence of external object  46  adjacent to transmit antenna  40 TX. Curve  60  plots the magnitude of reflection S-parameter S 11  (i.e., |S 11 |) as a function of frequency in the absence of external object  46  within threshold range R TH . As shown by curve  60 , in the absence of external object  46 , |S 11 | may have a relatively high value across a frequency band of interest B (e.g., the frequency band used to convey radio-frequency signals  38  or  42  of  FIG.  1   ). 
     Curve  62  plots |S 11 | as a function of frequency when external object  46  is within threshold range R TH  from transmit antenna  40 TX. As shown by curve  62 , |S 11 | may have a relatively low value across frequency band B due to the presence of external object  46 . In general, once external object  46  is within threshold range R TH , |S 11 | will continue to decrease, as shown by arrow  64  as the object approaches transmit antenna  40 TX. Control circuitry  14  may gather VSWR values using VSWR sensor  32  (e.g., |S 11 | values such as those shown by curves  60  and  62 ) and may process the gathered VSWR values to identify when external object  46  is within threshold range R TH  (e.g., by comparing the gathered Bill values to one or more threshold levels). Beyond threshold range R TH , |S 11 | will exhibit no change or a negligible change in response to changes in distance between transmit antenna  40 TX and external object  46 . At these relatively far distances, long range spatial ranging circuitry  28  ( FIG.  1   ) may be used to detect the presence, position (e.g., range R), and/or velocity of external object  46 . 
       FIG.  3    is a circuit diagram showing how VSWR sensor  32  may be disposed on transmit path  34 . As shown in  FIG.  3   , transmit path  34  may include a power amplifier (PA) such as PA  96 . The input of PA  96  may be coupled to long range spatial ranging circuitry  28  and/or communications circuitry  26  of  FIG.  1   . The output of PA  96  may be coupled to transmit antenna  40 TX via a switch such as antenna switch  94 . The output of PA  96  may also be coupled to matched load  88  via a switch such as matched load switch  90 . Matched load  88  may be coupled in series between matched load switch  90  and ground  82 . Matched load  88 , matched load switch  90 , and/or antenna switch  94  may be omitted if desired. 
     In the example of  FIG.  3   , VSWR sensor  32  is a directional switch coupler. This is merely illustrative and, in general, VSWR sensor  32  may be implemented using any desired VSWR sensor architecture. As shown in  FIG.  3   , VSWR sensor  32  may include directional coupler  72  interposed on transmit path  34  between PA  96  and transmit antenna  40 TX (e.g., along a radio-frequency transmission line in transmit path  34  coupled between the output of PA  96  and transmit antenna  40 TX). Directional coupler  72  may have a first port (P 1 ) coupled to the output of PA  96  and a second port (P 2 ) communicably coupled to transmit antenna  40 TX. Directional coupler  72  may have a third port (P 3 ) coupled to a first termination that includes resistor  84  coupled in series between termination switch  78  and ground  82 . Directional coupler  72  may also have a fourth port (P 4 ) coupled to a second termination that includes resistor  86  coupled in series between termination switch  80  and ground  82 . VSWR sensor  32  may have a forward (FW) switch  74  coupled between port P 3  and measurement circuitry  70  (e.g., an amplitude and/or phase detector). VSWR sensor  32  may also have a reverse (RW) switch  76  coupled between port P 4  and measurement circuitry  70 . 
     Measurement circuitry  70  may have a control path coupled to other components in USR detector  30  or control circuitry  14  ( FIG.  1   ) and/or some or all of measurement circuitry  70  may form a part of control circuitry  14  (e.g., the operations of some or all of measurement circuitry  70  may be performed using one or more processors). Measurement circuitry  70  may include, for example, a power detector such as power detector  98 , an in-phase and quadrature-phase (I/Q) detector (e.g., an ADC), logic such as comparator/logic  102  (e.g., one or more logic gates, etc.), and/or memory such as memory  104 . Memory  104  may form a part of storage circuitry  16  of  FIG.  1   , for example. If desired, I/Q detector  100  may be formed from one or more ADCs in receive path  36  ( FIG.  1   ). 
     When performing VSWR measurements (e.g., S-parameter values such as Sri values), PA  96  may output a transmit test signal sigtx (e.g., while antenna switch  94  is closed). Test signal sigtx may be a radar transmit signal transmitted by long range spatial ranging circuitry  28  (e.g., radio-frequency signals  42  of  FIG.  1   ), a wireless communications data transmit signal transmitted by communications circuitry  26  (e.g., radio-frequency signals  38  of  FIG.  1   ), or a dedicated test signal for use in VSWR measurement (e.g., one or more tones transmitted by a signal generator, local oscillator, and/or other signal generation circuitry in USR detector  30  of  FIG.  1   ). For example, a sequential signal generator  108  may be used to generate test signal sigtx. Sequential signal generator  108  may be a part of long range spatial ranging circuitry  28  (e.g., test signal sigtx may be a continuous wave or wideband that can also be used in performing long range spatial ranging operations), may be a part of communications circuitry  26  (e.g., test signal sigtx may also carry wireless communications data), or may be formed as a part of USR detector  30  that is separate from long range spatial ranging circuitry  28  and communications circuitry  26 . Additionally or alternatively, a simple local oscillator such as local oscillator (LO)  106  may generate test signal sigtx. 
     In performing VSWR measurements, VSWR sensor  32  may perform forward path measurements and reverse path measurements using transmit signal sigtx. When performing forward path measurements, FW switch  74  is closed, RW switch  76  is open, switch  80  is closed, and switch  78  is open so that test signal sigtx is coupled off from transmit path  34  by directional coupler  72  and routed to measurement circuitry  70  through FW switch  74 . Measurement circuitry  70  may measure and store the amplitude (magnitude) and/or phase of test signal sigtx for further processing (e.g., as a forward signal phase and magnitude measurement). For example, power detector  98  (e.g., a peak detector, diode and capacitor, etc.) may measure the magnitude of test signal sigtx and may store the magnitude on memory  104 . As another example, I/Q detector  100  may make I/Q measurements for the forward path that are stored on memory  104 . 
     At least some of test signal sigtx will reflect off of transmit antenna  40 TX (e.g., due to impedance discontinuities between transmit path  34  and transmit antenna  40 TX subject to impedance loading from any external objects at or adjacent to transmit antenna  40 TX) and back towards PA  96  as reflected test signal sigtx′. When performing reverse path measurements, FW switch  74  is open, RW switch  76  is closed, switch  80  is open, and switch  78  is closed so that reflected test signal sigtx′ is coupled off of transmit path  34  by directional coupler  72  and routed to measurement circuitry  70  through RW switch  76 . Measurement circuitry  70  (e.g., power detector  98  or I/Q detector  100 ) may measure and store the amplitude (magnitude) and/or phase of reflected test signal sigtx′ for further processing (e.g., as a reverse signal phase and magnitude measurement). Comparator/logic  102  and/or control circuitry  14  ( FIG.  1   ) may process the stored forward and reverse phase and magnitude measurements to identify complex scattering parameter values such as S 11  values. The S 11  values are characterized by a scalar magnitude |S 11 | and a corresponding phase. In this way, VSWR sensor  32  may measure VSWR values (e.g., S 11  values, |S 11 | values, etc.) that can be used to determine when external object  46  is located at a range R that is less than or equal to threshold range R TH . Long range spatial ranging circuitry  28  ( FIG.  1   ) may also use transmit antenna  40 TX to identify range R when external object  46  is located at a range R that is beyond threshold range R TH  from transmit antenna  40 TX. 
     It may be desirable for USR detector  30  to be able to distinguish between animate external objects  46  and inanimate external objects  46  in the vicinity of transmit antenna  40 TX (e.g., within threshold range R TH  from transmit antenna  40 TX). For example, inanimate objects may not be subject to regulatory limits on SAR or MPE, whereas animate objects are likely to be human body parts that are subject to regulatory limits on SAR or MPE. If USR detector  30  is able to detect that an external object  46  present within threshold range R TH  of transmit antenna  40 TX is an inanimate object, wireless circuitry  24  may be able to continue to transmit signals over transmit antenna  40 TX at relatively high transmit power levels (e.g., the maximum transmit power level of PA  96 ) without violating regulatory limits on SAR or MPE. This may serve to maximize the wireless performance of device  10  in performing wireless communications and/or long range spatial ranging operations relative to scenarios where the wireless circuitry has to reduce transmit power level or maximum transmit power level in the presence of any external object within threshold range R TH  regardless of whether the external object is animate or inanimate. At the same time, if USR detector  30  is able to detect that an external object  46  present within threshold range R TH  of transmit antenna  40 TX is an animate object, wireless circuitry  24  may have relatively high confidence that the external object is a body part subject to SAR/MPE limits and may therefore reduce the transmit power level or the maximum transmit power level for transmit antenna  40 TX to ensure that regulatory limits on SAR or MPE are satisfied. 
     If desired, control circuitry  14  ( FIG.  1   ) may use variations in the VSWR measurements performed by VSWR sensor  32  over time to determine whether an external object  46  adjacent to transmit antenna  40 TX is animate or inanimate.  FIG.  4    is a plot showing how VSWR measurements (e.g., |S 11 | values) performed by VSWR sensor  32  may vary over time in the presence of an external object adjacent to transmit antenna  40 TX. 
     Curve C 1  of  FIG.  4    illustrates |S 11 | values that may be generated by measurement circuitry  70  ( FIG.  3   ) at different frequencies and at a first time (e.g., in response to test signals sigtx that are swept over a range of frequencies). Curve C 2  illustrates |S 11 | values that may be generated by measurement circuitry  70  at different frequencies and at a second time. As shown by curves C 1  and C 2 , the |S 11 | measurements gathered by measurement circuitry  70  may vary at a given frequency F by difference (variation)  110  between the first and second times. In general, animate objects will produce more variation in the |S 11 | measurements at a given frequency over time than inanimate objects. Control circuitry  14  may therefore gather a sufficient number of VSWR measurements over time, may process the VSWR measurements to identify differences (variations) in the VSWR measurements over time (e.g., differences such as difference  110  of  FIG.  4   ), and may process the identified differences to determine whether external object  46  is inanimate or animate. The example of  FIG.  4    is merely illustrative and, in practice, curves C 1  and C 2  may have other shapes. 
     Some examples of inanimate objects  46  that may be present adjacent to transmit antenna  40 TX include furniture, tabletops, desktops, vehicle dashboards, or removable device cases (e.g., removable plastic cases, rubber cases, leather cases, cases with a combination of materials, etc.) for device  10 . If desired, control circuitry  14  may also use the identified differences (variations) in VSWR measurements over time to determine whether device  10  has been placed within a removeable case (e.g., to determine whether external object  46  is a removable case for device  10 ). Since different users will place device  10  into different types of removable cases having different dielectric properties, control circuitry  14  may further determine what type of removable case is present and/or the effects of the removable case for calibrating other device operations if desired. For example, control circuitry  14  may use the presence of the removable case and/or information about the type of removable case that is present to calibrate subsequent radar operations performed by long range spatial ranging circuitry  28  (e.g., to adjust estimates of range R to account for the path loss effects of the transmitted and received signals which have to pass through the removable case), to adjust the impedance matching and/or tuning of transmit antenna  40 TX (e.g., to compensate for dielectric loading by the removable case to minimize signal reflections at the transmit antenna and so that the transmit antenna is not undesirably detuned away from its desired operating frequency), to adjust future VSWR measurements, etc. 
       FIG.  5    is a plot of different reflection coefficient (return loss) magnitude measurements (|S 11 | values) that may be made by VSWR sensor  32  as a function of time in the presence of different types of external objects  46 . Points  114  of  FIG.  5    illustrate |S 11 | measurements made by VSWR sensor  32  in the absence of any external objects (e.g., at five different sampling times such as times T 0 , T 1 , T 2 , T 3 , and T 4 ). Points  114  may, for example, be predetermined points that are generated during factory calibration of device  10 . As shown by points  114 , there is relatively little variation in |S 11 | (e.g., no variation) as a function of time in the absence of external objects. 
     Points  112  illustrate |S 11 | measurements that may be made by VSWR sensor  32  at times T 0 -T 4  in the presence of an inanimate object adjacent to transmit antenna  40 TX. The inanimate object may be, for example, a removable case for device  10 . As shown by points  112 , there is relatively little variation in |S 11 | as a function of time in the presence of an inanimate object such as a removable device case. Control circuitry  14  may compare points  112  to predetermined points  114  to determine that an inanimate object such as a removable device case is present. If desired, control circuitry  14  may compare points  114  to other predetermined points that are known to be associated with different types of removable device cases (e.g., predetermined points stored on device  10  during factory calibration in the presence of the different types of removable cases) to identify the type of removable device case that is present. 
     Points  116  illustrate |S 11 | measurements that may be made by VSWR sensor  32  at times T 0 -T 4  in the presence of an animate object adjacent to transmit antenna  40 TX. The animate object may be, for example, a body part. As shown by points  116 , there is a relatively high amount of variation in |S 11 | as a function of time in the presence of an animate object such as a body part (e.g., due to minute movements of the external object relative to static/inanimate objects such as a removable device case). Control circuitry  14  may perform animate object detection by performing |S 11 | measurements at different times (e.g., times T 0 -T 4 ) to produce points such as points  114 ,  112 , or  116  of  FIG.  5   . Control circuitry  14  may identify variations in the |S 11 | measurements over time to determine whether an external object adjacent to transmit antenna  40 TX is an inanimate object (and if so, whether the inanimate object is a device case and optionally the type of device case) or an animate object that is subject to regulatory limits on SAR/MPE. 
     Control circuitry  14  may perform animate object detection based on any desired metric for the variation of VSWR (e.g., |S 11 |) measurements over time. For example, control circuitry  14  may perform animate object detection based on the difference between the maximum |S 11 | value and the minimum Bill value measured at each of the sampling times. For points  116 , control circuitry  14  may identify (e.g., compute, calculate, generate, determine, etc.) a difference value Δ that is equal to the difference between the maximum |S 11 | value |S 11 |MAX of points  116  (e.g., as measured at time T 1 ) and the minimum |S 11 | value |S 11 |MIN of points  116  (e.g., as measured at time T 2 ). For points  112 , this difference value is relatively small (or zero in scenarios where each point  112  is at the same IS ill). Control circuitry  14  may compare difference value Δ to one or more threshold values to determine whether the external object is animate or animate (e.g., if difference value Δ exceeds the threshold value, control circuitry  14  may determine that the external object is animate). This example is merely illustrative and, in general, control circuitry  14  may identify any desired metric of variance in |S 11 | for comparison to one or more threshold values in determining whether the external object is animate or inanimate. As another example, control circuitry  14  may identify the mean and variance of the Bill measurements over time, the rate of change of |S 11 | measurements over time, and/or any other desired variation metrics for comparison to one or more threshold values for determining whether the external object is animate or inanimate. 
     The example of  FIG.  5    is merely illustrative. Points  114 ,  116 , and  112  may have other values in practice. In the example of  FIG.  5   , five sampling times T 0 -T 4  are used to identify variations in |S 11 | for performing animate object detection. This is merely illustrative and, in general, any desired number n of sampling times may be used to identify variations in |S 11 | for performing animate object detection. Each sampling time may be separated by 10 ms, 20 ms, 1-20 ms, more than 20 ms, 10-50 ms, or any other desired period. The sampling times need not be evenly spaced. 
       FIG.  6    is a plot of return loss (e.g., |S 44 |) as a function of frequency illustrating the effects of different removable cases on VSWR measurements by VSWR sensor  32 . Curve  122  plots |S 44 | in the absence of a removable case and any other external object. Curve  118  plots |S 44 | in the presence of a first type of removable case (e.g., a removable case made from a first material, having a first thickness, etc.). Curve  120  plots |S 44 | in the presence of a second type of removable case (e.g., a removable case made from a second material, having a second thickness, etc.). 
     As shown by curves  122 ,  120 , and  118 , the presence of a removable case causes a shift in the magnitude of the VSWR measurements made by VSWR sensor  32  (also shown by the difference between points  112  and points  114  of  FIG.  5   ). As shown by curves  120  and  118 , different types of cases may have different effects on the VSWR measurements made by VSWR sensor  32 . However the same variations in VSWR measurements are made in the presence of either type of removable case or in the absence of any external object as a function of time (e.g., as shown by points  114  or  112  of  FIG.  5   ). Control circuitry  14  may compare the VSWR measurements to expected VSWR measurements associated with different removable case types (e.g., curves  118  and  120 ) to identify what type of removable case is present on device  10  if desired. In other words, control circuitry  14  may compare variations in the VSWR measurements over time to one or more thresholds for performing animate object detection and may further compare the magnitude of the VSWR measurements (or the magnitude of an average of the VSWR measurements) to one or more thresholds for performing removable case detection and identification. The example of  FIG.  6    is merely illustrative. Curves  118 - 122  may have other shapes in practice. 
       FIG.  7    is flow chart of illustrative operations involved in using VSWR sensor  32  to determine whether external objects adjacent to transmit antenna  40 TX are animate or inanimate. At operation  124 , a given sampling period in which VSWR sensor  32  performs VSWR measurements (samples) for performing animate object detection may begin. The sampling period may begin periodically (e.g., at a predetermined time, between other scheduled communications or signal transmissions, etc.) or may begin in response to a trigger condition. The sampling period may begin, for example, once VSWR sensor  32  has already detected that external object  46  has passed within threshold range R TH  of transmit antenna  40 TX (e.g., once VSWR measurements such as |S 11 | measurements reach a predetermined threshold value). 
     As another example, the sampling period may begin once device  10  has determined that gathered wireless performance metric data has fallen outside of a predetermined range. In this example, wireless circuitry  24  may gather wireless performance metric data associated with the radio-frequency performance of transmit antenna  40 TX and/or receive antenna  40 RX. The wireless performance metric data may include signal-to-noise ratio (SNR) data, receive signal strength indicator (RSSI) data, or any other desired performance metric data gathered during the transmission of radio-frequency signals  38 , the transmission of radio-frequency signals  42 , the reception of radio-frequency signals  38 , and/or the reception of reflected signals  44  of  FIG.  1   , for example. Control circuitry  14  may compare the gathered wireless performance metric data with a predetermined range of wireless performance metric values associated with satisfactory radio-frequency performance and/or the operation of wireless circuitry  24  in the absence of external objects within threshold range R TH  (e.g., a predetermined range of satisfactory RSSI values, SNR values, etc.). The predetermined range of wireless performance metric values may be characterized by an upper threshold limit or value and/or a lower threshold limit or value. 
     The wireless performance metric data may serve as a coarse indicator for whether external object  46  is within threshold range R TH . For example, if external object  46  is within range R TH , external object  46  may partially block or cover one or more antennas  40  (thereby preventing the antenna from properly receiving radio-frequency signals), may undesirably load or detune one or more antennas  40  in device  10 , etc. When the gathered wireless performance metric data falls outside of the predetermined range, this may be indicative of the potential presence of external object  46  within threshold range R TH . However, when the gathered wireless performance metric data falls within the predetermined range, this may indicate that it is very unlikely that there is an external object present within threshold range R TH  (e.g., because wireless circuitry  24  is performing nominally as expected in the absence of an external object within threshold range R TH ). If the gathered wireless performance metric data falls within the predetermined range (thereby indicating that there is no external object within threshold range R TH ), VSWR sensor  32  may gather background VSWR measurements for performing background cancellation if desired. 
     VSWR sensor  32  may make n VSWR measurements such as |S 11 | measurements (sometimes referred to herein as samples) during any given sampling period. Each of the n VSWR measurements may occur at a corresponding sampling time within the sampling period (e.g., at times T 0 -T 4  of  FIG.  5   ). The sampling period may be any desired length (e.g., n may be any desired integer such as 2, between 3-5, between 5-10, between 10-20, 100, more than 100, more than 10, more than 20, more than 5, more than 2, etc.). 
     At operation  126 , wireless circuitry  24  (e.g., sequential signal generator  108  or LO  106  of  FIG.  3   ) may transmit test signal sigtx over transmit path  34 . Test signal sigtx may be transmitted at a single frequency (e.g., a single tone), at multiple frequencies (e.g., as a dual tone or multiple tones), or may be swept over a range of frequencies. Transmit antenna  40 TX may transmit test signal sigtx. If desired, transmit antenna  40 TX may forego transmission of test signal sigtx (e.g., antenna switch  94  of  FIG.  3    may be open). 
     At operation  128 , VSWR sensor  32  may perform a VSWR measurement (e.g., may gather an |S 11 | value) from the transmitted test signal sigtx (or multiple VSWR measurements in scenarios where test signal sigtx is swept over a range of frequencies) and may store the VSWR measurement(s) for subsequent processing (e.g., on memory  104  of  FIG.  3   ). This measurement may occur at a corresponding sampling time within the sampling period (e.g., one of times T 0 -T 4  of  FIG.  5   ). If the full sampling period has not yet elapsed (e.g., if fewer than n samples or iterations of operations  126 - 128  have taken place for the current sampling period), processing may loop back to operation  126  via path  130 . Each iteration of operations  126 - 128  may take a corresponding duration or period to perform (e.g., 10 ms, 20 ms, 1-20 ms, more than 20 ms, etc.). Each VSWR measurement (e.g., each iteration of operation  128 ) may therefore be separated in time, thereby allowing VSWR measurements to be made over time (e.g., over the sampling period) for identifying variations in the VSWR measurements over time for subsequent processing. 
     If the sampling period has elapsed (e.g., once n samples or iterations of operations  126 - 128  have taken place), processing may proceed from operation  128  to operation  134  via path  132 . At operation  134 , control circuitry  14  (e.g., comparator/logic  102  of  FIG.  3    or other control circuitry separate from measurement circuitry  70  of  FIG.  3   ) may identify an amount of variation over time in the VSWR measurements gathered and stored during the sampling period. For example, control circuitry  14  may identify a variation metric such as difference value Δ for the VSWR measurements, which is equal to the difference between the maximum stored |S 11 | value (e.g., |S 11 |MAX of  FIG.  5   ) and the minimum stored |S 11 | value (e.g., |S 11 |MIN of  FIG.  5   ) from the sampling period. This is merely illustrative and, in general, control circuitry  14  may identify other variation metrics such as the mean and variance of the stored |S 11 | values if desired. 
     At operation  136 , control circuitry  14  may perform animate object detection based on the identified variation in the VSWR measurements gathered and stored during the sampling period. For example, control circuitry  14  may compare the identified variation (e.g., difference value Δ) to one or more threshold values indicative of whether external object  46  is animate or inanimate. The animate object detection may allow control circuitry  14  to distinguish between external objects  46  that are inanimate, such as a tabletop or removable case, from external objects  46  that are animate, such as a body part of the user of device  10  or other persons. 
     If desired, control circuitry  14  may process the VSWR measurements gathered and stored during the sampling period to identify whether a removable case is present on device  10  and to optionally identify what type of removable case is present on device  10  (at operation  138 ). These case detection operations may be performed in response to identifying that external object  46  is an inanimate object, for example. 
     If desired, control circuitry  14  may identify a range to external object  46  based on the identified variation in the VSWR measurements gathered and stored during the sampling period (at operation  140 ). Control circuitry  14  may, for example, compare the identified variation to one or more threshold values indicative of the presence of external object  46  at different ranges within threshold range R TH . 
     If desired, control circuitry  14  may reduce the transmit power level of antenna  40 TX, may reduce the maximum transmit power level of antenna  40 TX (e.g., the upper limit or cap on transmit power levels used by antenna  40 TX), may switch a different transmit antenna into use, and/or may disable transmit antenna  40 TX in response to determining that external object  46  is an animate object. This may ensure that animate external objects, which are possibly or even likely human body parts, are not exposed to excessive radio-frequency energy, thereby ensuring that device  10  continues to satisfy any regulatory limits on SAR or MPE. 
     The example of  FIG.  7    is merely illustrative. Operations  138 ,  140 , and/or  142  may be omitted. Control circuitry  14  may perform any other desired operations in response to the detection of an animate external object or an inanimate external object adjacent transmit antenna  40 TX. If desired, control circuitry  14  may increase the transmit power level, may increase the maximum transmit power level, and/or may switch transmit antenna  40 TX into use in response to determining that external object  46  is an inanimate object. 
       FIG.  8    is a flow chart of illustrative operations involved in performing animate object detection. The operations of  FIG.  8    may be performed by control circuitry  14  (e.g., one or more processors separate from and/or including portions of measurement circuitry  70  of  FIG.  3   ) in performing operation  136  of  FIG.  7   , for example. 
     At operation  144  of  FIG.  8   , control circuitry  14  may compare the identified variation in VSWR measurements for the sampling period to a minimum variation threshold value. For example, control circuitry  14  may compare difference value Δ to the minimum variation threshold value. If the identified variation (e.g., difference value Δ) exceeds the minimum variation threshold value (e.g., if there is a sufficient amount of variation in |S 11 | over the sampling period), processing may proceed to operation  148  via path  146 . 
     At operation  148 , control circuitry  14  may identify that external object  46  is an animate (non-static) external object (e.g., because the relatively high amount of variation in |S 11 | values gathered over the sampling period is indicative of an external object that moves at least slightly adjacent transmit antenna  40 TX, which is characteristic of a possible human body part). If desired, control circuitry  14  may reduce the transmit power level of transmit antenna  40 TX, may reduce the maximum transmit power level of transmit antenna  40 TX, may disable transmit antenna  40 TX, may switch a different transmit antenna into use, and/or may perform any other desired processing in response to determining that external object  46  is an animate object (e.g., software applications running on device  10  may use the presence of an animate object adjacent to the device as a control input, etc.). This may ensure that device  10  continues to satisfy regulatory limits on SAR/MPE given the potential (or likely) presence of a body part near to transmit antenna  40 TX. 
     At optional operation  150 , control circuitry  14  may identify the range to external object  46  based on the identified variation in stored VSWR measurements. For example, the amount of variation in the stored VSWR measurements may be correlated to the range between the animate external object and transmit antenna  40 TX. Control circuitry  14  may compare the identified variation (e.g., difference value Δ) to one or more additional threshold values indicative of the animate external object being located at different distances from transmit antenna  40 TX to identify the range between device  10  and the animate external object. Control circuitry  14  may use the identified range for any other desired processing or application tasks. Optional operation  150  may be omitted if desired. 
     If the identified variation (e.g., difference value Δ) is less than the minimum variation threshold value (e.g., if there is an insufficient amount of variation in |S 11 | over the sampling period), processing may proceed from operation  144  to operation  154  via path  152 . At operation  154 , control circuitry  14  may identify that external object  46  is an inanimate (static) external object (e.g., because the relatively low amount of variation in |S 11 | values gathered over the sampling period is indicative of an external object that does not move, unlike a human body part). If desired, control circuitry  14  may forego decreasing the transmit power level or the maximum transmit power level of transmit antenna  40 TX. In other words, control circuitry  14  may maintain the current maximum transmit power level of transmit antenna  40 TX or may increase the maximum transmit power level of transmit antenna  40 TX. If desired, control circuitry  14  may increase the transmit power level of transmit antenna  40 TX, may switch transmit antenna  40 TX into use, and/or may perform any other desired processing in response to determining that external object  46  is an inanimate object (e.g., software applications running on device  10  may use the presence of an inanimate object adjacent to the device as a control input, etc.). This may help to maximize the radio-frequency performance of wireless circuitry  24  in performing wireless communications and/or long range spatial ranging operations (e.g., maximizing throughput, signal quality, signal-to-noise ratio, etc.) relative to scenarios where transmit power level or maximum transmit power level is reduced for all external objects  46  within threshold range R TH  regardless of whether the external object is animate or inanimate. Because the inanimate object is not a human body part, omitting a reduction in transmit power level or maximum transmit power level will not cause device  10  to exceed regulatory limits on SAR/MPE. 
     If desired, control circuitry  14  may also perform case detection at operation  154 . For example, control circuitry  14  may compare one or more of the stored VSWR measurements (or an average of the stored VSWR measurements) to one or more predetermined VSWR measurements (e.g., |S 11 | values) stored on device  10  to determine whether a removable case is present on device  10 . The predetermined VSWR measurements may be, for example, expected VSWR measurements gathered for device  10  (e.g., during factory calibration) in the absence of any external objects or a removable case (e.g., one or more of points  114  or an average of points  114  of  FIG.  5   ). 
     If the difference between the stored VSWR measurement(s) and the predetermined VSWR measurement(s) is less than a threshold difference value (or if the stored VSWR measurements are otherwise sufficiently similar to the predetermined VSWR measurements), processing may proceed to operation  158  via path  156 . At operation  158 , control circuitry  14  may identify that the inanimate external object is not a removable case or is not present adjacent transmit antenna  40 TX. However, if the difference between the stored VSWR measurement(s) and the predetermined VSWR measurement(s) exceeds the threshold difference value (or if the stored VSWR measurements are sufficiently dissimilar to the predetermined VSWR measurements), processing may proceed to optional operation  162  via path  160 . 
     At optional operation  162 , control circuitry  14  may identify a type of removable case present on device  10 . For example, control circuitry  14  may compare one or more of the stored VSWR measurements (e.g., an average of the stored VSWR measurements, the VSWR measurements as a function of frequency) to one or more predetermined VSWR measurements stored on device  10  to determine the type of removable case present. These predetermined VSWR measurements may be, for example, expected VSWR measurements gathered for device  10  (e.g., during factory calibration) while placed into a variety of different removable case types. As an example, control circuitry  14  may compare the stored VSWR measurements to curves such as curves  118  and  120  of  FIG.  6    to determine whether the removable cases associated with curves  118  or  120  are present on device  10 . If desired, operation  162  may be combined with operation  154  (e.g., control circuitry  14  may compare the stored VSWR measurements to the predetermined VSWR measurements associated with different types of removable cases and, if the VSWR measurements are not sufficiently similar to any of the predetermined VSWR measurements, processing may proceed from operation  154  to operation  158 ). Operation  162  may be omitted if desired. 
     At operation  164 , control circuitry  14  may identify that the inanimate external object is a removable device case (and optionally the type of removable device case). Control circuitry  14  may perform additional processing based on the detected presence of the removable device case and/or the identified type of case. For example, control circuitry  14  may use VSWR sensor  32  to gather background VSWR measurements in the absence of other external objects within threshold range R TH , where the background VSWR measurements take into account the presence of the removable device case. Control circuitry  14  may then use the background VSWR measurements to perform background cancellation on subsequent VSWR measurements that are gathered in the presence of another external object within threshold range R TH  while device  10  is placed within the removable case (e.g., by subtracting the background VSWR measurements from the subsequent VSWR measurements). In other words, VSWR detector  32  may perform VSWR background cancellation based on the detected presence of the removable device case on device  10 . As another example, control circuitry  14  may control the impedance matching and/or antenna tuning of transmit antenna  40 TX based on the presence of the removable device case and optionally the type of removable device case (e.g., to compensate for impedance loading or detuning of the antenna on account of the presence of the removable device case). As yet another example, control circuitry  14  may use the presence of the removable case and optionally the type of removable case to calibrate long range spatial ranging operations performed using transmit antenna  40 TX (e.g., to compensate for path delay effects of the transmitted and/or reflected signals passing through the removable case). 
     Curve  168  of  FIG.  9    shows one example of how variation in |S 11 | may be correlated with the range between the external object and transmit antenna  40 TX. If desired, control circuitry  14  may compare the identified variation in the stored VSWR measurements to curve  168  to identify the corresponding range between the external object and transmit antenna  40 TX (e.g., while processing operation  150  of  FIG.  8   ). Curve  168  may be stored on device  10  (e.g., during factory calibration, manufacture, assembly, testing, etc.). The example of  FIG.  9    is merely illustrative and, in practice, curve  168  may have other shapes. 
       FIG.  10    shows two exemplary timing diagrams for performing VSWR measurements for use in performing animate object detection. Timing diagram  170  illustrates one arrangement in which VSWR measurements for performing animate object detection are time-interleaved (time-multiplexed) with other transmit operations. During sampling periods  172 , control circuitry  14  may perform n iterations of operations  126  and  128  of  FIG.  7   . The n VSWR measurements during each sampling period  172  may be processed to identify a corresponding variation and the variation may be processed to determine whether external object  46  is animate or inanimate (e.g., while processing operations  134 - 136 ). During periods  174 , transmit antenna  40 TX may be used to transmit other signals such as radar signals for performing long term spatial ranging or wireless communications signals. Operations  134 - 136  of  FIG.  7    may be performed during each sampling period  172  or may, if desired, extend into the subsequent period  174 . 
     Timing diagram  176  illustrates another arrangement in which VSWR measurements for performing animate object detection are performed during rolling sampling periods  172 . As shown by timing diagram  176 , each sampling period for identifying variation in VSWR measurements may include a subset of the samples from the previous sampling period as well as additional samples after the previous sampling period has elapsed. This may allow wireless circuitry  24  to continuously determine whether external object  46  is animate or inanimate, for example. The examples of  FIG.  10    are merely illustrative. The timing arrangements of timing diagrams  170  and  176  may be combined if desired. The signals transmitted during periods  174  may be used as test signal sigtx if desired (e.g., separate sampling periods  172  may be omitted). Other timing arrangements for sampling period  172  may be used if desired. 
     The methods and operations described above in connection with  FIGS.  1 - 10    may be performed by the components of device  10  using software, firmware, and/or hardware (e.g., dedicated circuitry or hardware). Software code for performing these operations may be stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media) stored on one or more of the components of device  10  (e.g., storage circuitry  16  of  FIG.  1   ). The software code may sometimes be referred to as software, data, instructions, program instructions, or code. The non-transitory computer readable storage media may include drives, non-volatile memory such as non-volatile random-access memory (NVRAM), removable flash drives or other removable media, other types of random-access memory, etc. Software stored on the non-transitory computer readable storage media may be executed by processing circuitry on one or more of the components of device  10  (e.g., processing circuitry  18  of  FIG.  1   , etc.). The processing circuitry may include microprocessors, central processing units (CPUs), application-specific integrated circuits with processing circuitry, or other processing circuitry. The components of  FIGS.  1  and  3    may be implemented using hardware (e.g., circuit components, digital logic gates, etc.) and/or using software where applicable. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20210527
Publication Date: 20231010
Grant Date: 20231010
Priority Date: 20210527
Inventors: HUR, JOONHOI
MENKHOFF, ANDREAS
SOGL, BERNHARD
Schrattenecker, Jochen
VAZNY, RASTISLAV
Assignee: APPLE INC
CPC Classifications: [{"code": "G01S13/88", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S13/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/103", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S13/52", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S13/88", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R27/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L43/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S13/56", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S13/343", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01S13/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S7/4013", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S7/006", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01S7/358", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01S7/415", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S13/08", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 83997163