WO2019078837A1

WO2019078837A1 - Antennas to determine object presence

Info

Publication number: WO2019078837A1
Application number: PCT/US2017/057104
Authority: WO
Inventors: Ming-Shien Tsai; Yi-Kang Hsieh; Chung-Chun Chen
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2017-10-18
Filing date: 2017-10-18
Publication date: 2019-04-25

Abstract

A device includes antennas to transmit and receive data with a wireless network. The antennas include a first antenna and a second antenna. A processor is connected to the antennas and is to execute instructions. The instructions are to control the first antenna to emit a proximity signal, control the second antenna to receive a representation of the proximity signal, and determine a presence of an object in a path between the first antenna and the second antenna based on the representation of the proximity signal.

Description

ANTENNAS TO DETERMINE OBJECT PRESENCE

BACKGROUND

[0001] Computers and communications devices often include an antenna to facilitate communications with wireless networks. Antenna transmit power is often controlled for user heath, regulatory requirements, and other reasons. A proximity sensor is frequently used to detect a user's body in the vicinity of the antenna, so that power of the antenna may be controlled accordingly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 is a block diagram of an example device.

[0003] FIG. 2 is a block diagram of the example device of FIG. 1 during an example operation.

[0004] FIG. 3 is a flowchart of an example method of proximity detection.

[0005] FIG. 4 is a flowchart of an example method of proximity detection and transmit power control.

[0006] FIG. 5 is a plan view of another example device.

[0007] FIG. 8 is a plan view of the example device of FIG. 5 during an example operation.

[0008] FIG. 7 is a block diagram of an example multiple input, multiple output device.

[0009] FIG. 8 is a flowchart of an example method of transmit power control based on continued presence detection. [0010] FIG. 9 is a schematic diagram of an example data structure.

DETAILED DESCRIPTION

[001 1] A proximity sensor takes up space and adds complexity to a device. When more than one antenna is used, several proximity sensors may be needed to detect proximity of a user's body to the various antennas.

[0012] Two or more antennas may be used together as an active proximity sensor to, for example, control transmit power to meet a specific absorption rate (SAR) requirement or other requirement, such as a Federal Communications Commission (FCC) requirement for SAR. A device may include a plurality of multiple input, multiple output (Ml MO) antennas. An antenna may emit a proximity signal and another antenna may receive the proximity signal, A characteristic of the received proximity signal may be taken as an indication of the presence of a user's body in an electromagnetic (EM) path between the antennas. Any single, combination, or permutation of paths between antennas may be used. As such, transmit power of any antenna may be controlled according to determined object presence or absence. A dedicated proximity sensor may be omitted from the device.

[0013] FIG. 1 shows an example device 10. The device 10 may be a computer device, such as a notebook computer, laptop computer, desktop computer, tablet computer, smartphone, and the like,

[0014] The device 10 includes a plurality of antennas 12, 14 and a processor 16 connected to the antennas 12, 14. Instructions 18, which may be termed proximity detection instructions, are provided for execution by the processor 16 to determine the presence of an object in a path 20 between the antennas 12, 14.

[0015] The plurality of antennas 12, 14 is to transmit and receive data with a wireless network. The antennas may be referred to as a first antenna 12 and a second antenna 14. The terms, first, second, third, etc. are merely used to distinguish elements from one another and do not limit the features, geometry, placement, order, and other properties of the elements. The antennas 12, 14 may form a Ml MO or other type of array of antennas.

[0016] The processor 18 may include a central processing unit (CPU), a microcontroller, a microprocessor, a processing core, a field-programmable gate array (FPGA), or similar device capable of executing instructions. The processor 16 may cooperate with memory to execute instructions. Memory may include a non-transitory machine-readable storage medium that may be any electronic, magnetic, optical, or other physical storage device that stores executable instructions. The machine-readable storage medium may include, for example, random access memory (RAM), read-only memory (ROM), electrically-erasable programmable read-only memory (EEPROM), flash memory, a storage drive, an optical disc, and the like. The machine-readable storage medium may be encoded with executable instructions.

[0017] The processor 16 is to execute the proximity detection instructions 18. The instructions 18 are to control the first antenna 12 to emit a proximity signal and to control the second antenna 14 to receive a representation of the proximity signal. Again, designations of first and second are not limiting and any antenna may be used to emit the proximity signal and any antenna may be used to receive a loopback proximity signal.

[0018] The instructions 18 are to determine a presence of an object in a path 20 between the first antenna 12 and the second antenna 14 based on the received representation of the proximity signal, which may exhibit a

characteristic, such as deceased strength, due to reflection, refraction, or other electromagnetic phenomenon caused by the object. That is, the instructions 18 may detect the presence of a human body sufficiently proximate to one or both of antennas 12, 14 to require a reduction of transmit power at one or both of the antennas 12, 14. The received proximity signal may be considered a loopback signal, as it may be processed by the same device that generated and emitted the proximity signal and further may be processed by the same

receiver/transmitter circuit that generated and emitted the proximity signal. [0019] The instructions 18 may be to control the first antenna 12 to emit the proximity signal and control the second antenna 14 to receive the

representation of the proximity signal intermittently between data

communications with the wireless network. That is, data communications with the wireless network may be briefly interrupted to detect for an object in the path 20 between the antennas 12, 14. For example, object detection may be performed periodically, such as every two seconds, on a scheduled basis, or by some other intermittent methodology.

[0020] The instructions 18 may determine a difference in signal strength between the emitted and received proximity signal and determine the presence of the object in the path between the first antenna 12 and the second antenna 14 based on the difference in signal strength.

[0021] The representation of the proximity signal received by the second antenna 14 may be a received signal strength indication (RSSI). The instructions 18 may compute an RSSI of the proximity signal as received by the second antenna 14 and compare the received RSSI to a nominal or expected RSSI to determine whether an object, such as part of a human body, has entered the EM path between the antennas 12, 14 to cause the loss in the proximity signal. An example expected RSSI may be that provided by the air gap between the antennas 12, 14. The instructions 18 may determine the difference between the received and expected RSSI by comparing the received RSSI to a threshold value. If the received RSSI is below the threshold value, then an object may be considered to be detected.

[0022] The representation of the proximity signal received by the second antenna 14 may be a decibel (dB) or decibel-milliwatts (dBm) power measurement.

[0023] In an example of operation, the instructions 18 control the first antenna 12 emit a proximity signal having predetermined waveform and power. At the same time, the instructions 18 control the second antenna 14 to receive a representation of the proximity signal and determine an RSSI. The instructions 18 then compare the received RSSI to a threshold value, where an RSSI below the threshold indicates that an object was detected.

[0024] The instructions 18 may be to control the transmit power of the first antenna 12 based on object detection. For example, the transmit power may be reduced when an object is detected and may be increased when an object is not detected.

[0025] The instructions 18 may be to perform the described functionality for each antenna 12, 14 of the device 10. That is, a proximity signal emitted by the first antenna 12 may be received by the second antenna 14 and a proximity signal emitted by the second antenna 14 may be received by the first antenna 12. Each received proximity signal may be referenced to control transmit power of the respective emitting antenna 12, 14.

[0026] The instructions 18 may be to control transmit power based on continued presence or absence of an object in a path 20 between antennas 12, 14. The instructions 18 may be to analyze a received proximity signal to determine whether the signal is transient or continued. Any suitable

characteristic of the received proximity signal may be used to differentiate between transient and continued presence of the object. More than one proximity signal received by different antennas may be analyzed to determine transient or continued presence or absence.

[0027] Monitoring for continued presence may be triggered by detection of transient proximity signal strength reduction in the path. The instructions 18 may be to intermittently check for a reduced-strength transient ioopback proximity signal at a receiver antenna in response to an emitted proximity signal at a transmitter antenna. If a transient Ioopback proximity signal is detected, the instructions 18 may be to monitor for a stabilized or continued reduced-strength Ioopback proximity signal. After a preset duration of continued presence, the instructions may be to reduce transmit power of an antenna 12, 14. Conversely, the same approach may be used to check for a transient and then continued !oopback proximity signal of strength indicative of no object present, and increase or restore antenna transmit power accordingly.

[0028] FIG, 2 shows an example operation of the example device 10,

[0029] The first and second antennas 2, 14 are to normally communicate signals with a wireless network 30. The wireless network 30 may include a wireless local-area network (WLAN), a wireless wide-area network (WWAN), a cellular network, and similar. The wireless network 30 may accord to a media access control (MAC) and physical layer (PHY) specification, such an Institute of Electrical and Electronics Engineers (IEEE™) 802.11 specification. For example, the wireless network 30 may operate according to IEEE 802.1 1ac, which provides frequency bands nominally at 2.4 GHz and 5 GHz, and which may be referred to as WI-FI. Communication between the antennas 12, 14 and the wireless network 30 may use any number of paths and may be performed according to a l MO methodology.

[0030] The instructions 18 may control the first antenna 12 to emit a proximity signal and control the second antenna to receive a representation of the proximity signal to detect an object 32 in a path 20 between the antennas 12, 14. The instructions 18 may be to control a transmit power of the first antenna 12 during normal data transmission to the wireless network 30 based on the representation of the proximity signal received at the second antenna 14, That is, upon detection of the object 32, the instructions 18 may reduce the transmit power that the first antenna 12 uses to transmit signals over a transmit path 34 to the wireless network 30.

[0031] The instructions 18 may be to further reduce a transmit power of the second antenna 14 even when the proximity signal is only emitted by the first antenna 12. That is, the path 20 between the antennas 12, 14 may be considered bidirectional even when only one direction is tested. In other examples, each antenna 12, 14 may be controlled to emit a proximity signal whose received representation is then referenced to control power of that antenna 12, 14. [0032] FIG. 3 shows a flowchart of an example method. The method may be performed by any of the devices discussed herein and may be performed continually during operation of a device. The method may be implemented by processor-executable instructions. The method starts at block 40.

[0033] At block 42, a signal is emitted from a first antenna of a device. The signal may be a proximity signal of predetermined waveform and strength. At block 44, the signal is received at a second antenna of the device. The first and second antennas may be Ml MO antennas provided to the device for communications with a wireless network. The method may be performed independently for each antenna of the device.

[0034] A characteristic of the signal received at the second antenna is determined, at block 46. The characteristic may be a strength or power measurement, such as RSSi.

[0035] At block 48, the characteristic of the received signal is compared to a parameter of the signal emitted from the first antenna. The parameter may be a transmitted power or strength, a reference RSSI, a threshold based on such, or similar. In one example, a threshold RSSi value is used. If the measured RSSI value exceeds the threshold, then the path between the antennas is considered clear of an object. If the measured RSSI value is below the threshold, then the path between the antennas is considered to have an object. Similarly, a received power may be directly compared to the emitted power multiplied by a reduction factor, such as 95%. Various other comparison computations are contemplated.

[0036] Based on the comparison, a presence of an object in a path between the first antenna and the second antenna is determined. If the measured characteristic of the received signal differs sufficiently from the parameter of the emitted signal, then an object is detected as proximate, at block 50. Otherwise, an object is not detected as proximate. The method ends at block 52. [0037] FIG. 4 shows a flowchart of another example method. The method may be performed by any of the devices discussed herein and may be performed continually during operation of a device. The method may be implemented by processor-executable instructions. The method starts at block 80.

[0038] At block 62, it is determined whether normal data communications are to be performed or whether proximity detection is to be performed. Proximity detection, by emitting and receiving signals among antennas of a device, may be performed intermittently between transmitting and receiving data signals between the antennas and a wireless network, at block 64. Intermittent proximity detection may be periodic, variable periodic, scheduled, irregular, or performed according to another temporal methodology. A frequency of proximity detection may be based on whether an object is detected. That is, transient detection of an object may trigger increased frequency of proximity detection to establish continued presence of the object.

[0039] When proximity detection is to be performed, the method performs blocks 42-50, which are described elsewhere herein. A signal is emitted by a first antenna of a device and received by a second antenna of the device, and a received signal characteristic is compared to a parameter used for the emission of the signal to determine whether an object is present in an EM path between the antennas and therefore proximate to the antennas.

[0040] A transmit power of the first antenna is reduced, at block 66, in response to determining the presence of the object in the path. Hence, a subsequent instance of data communication using the first antenna, at block 64, will occur at a lower power, so that a SAR requirement or similar transmit power restriction may be met Block 66 may also include reducing a transmit power of the second antenna, which may be useful if the method is not independently performed for the second antenna.

[0041] If an object is not determined to be proximate, then a transmit power of the first antenna may be increased or restored, at block 68, while complying with any maximum transmit power. As such, a subsequent instance of data communication using the first antenna, at block 64, may occur at a higher power. Block 68 may also include increasing or restoring a transmit power of the second antenna, which may be useful if the method is not independently performed for the second antenna,

[0042] The method ends at block 70. The method may be performed continually during operation of the device. Each time the method is performed, a transmit power may be increased or decreased based on detection of a proximate object in the path between the antennas. Data communication at block 64 may be performed using the transmit power set by blocks 42-50 and 66-68, which may be performed independently for each antenna.

[0043] FIG. 5 shows an example device 80. The device 80 may be a tablet computer, a screen portion of a notebook or laptop computer, a smartphone, or similar. The device 80 may include any of the features or aspects discussed herein.

[0044] The device 80 includes a plurality of antennas, such as a first antenna 82, a second antenna 84, a third antenna 86, and a fourth antenna 88. The antennas 82-88 may be Ml MO antennas. The example shown is a 4-by-4 Ml MO arrangement, in which the antennas 82-88 are arranged along one edge of the device 80.

[0045] The device 80 may include a display device 90, a camera module 92, a fan outlet 94, or similar components contained by a housing 96. The positions of these components may limit available space for one or more dedicated proximity sensors to sense proximity of a human body to the antennas 82-88. As such, the antennas 82-88 may be controlled to be proximity sensors, as described elsewhere herein, so that space need not be reserved for a dedicated proximity sensor.

[0046] A given antenna, such as antenna 84, may be used to emit a proximity signal that may be measured by one or more of the other antennas 82, 86-88, Any number and combination or permutation of antennas 82-88 may be used to emit and measure proximity signals. In the example illustrated, a proximity signal emitted by each antenna may be measured by up to three other antennas. Accordingly, this example may be used to implement up to 12 different proximity sensors, if direction of emission and reception is considered, or up to six different proximity sensors, if direction is ignored.

[0047] Instructions to control one or more antennas 82-88 to emit a proximity signal and one or more other antennas 82-88 to receive a representation of the proximity signal may allow for determining a presence of the object in one of the paths between the emitter antenna and each of the receiver antennas. For example, antenna 84 is controlled to emit a proximity signal and if a signal strength received by the antenna 82 is weakened to a greater degree than a signal strength received by the antenna 88, then the instructions may determine that the object is entirely or mainly in the path between antennas 84 and 82 as opposed to the path between antennas 84 and 88. A coarse indication of location of the object may be made and power of the antennas may be controlled accordingly.

[0048] FIG. 6 shows the example device 80 detecting the presence of an example object 100, such as a human hand. In this example, pairs of physically adjacent antennas are controlled to define active proximity sensors. That is, antennas 82, 84 define a first proximity sensor, antennas 84, 86 define a second proximity sensor, and antennas 86, 88 define a third proximity sensor. Processor-executable instructions provided to the device 80 may be to determine position and movement of the object based on signals emitted and received by the antennas 82-88. At the instant shown, the object 100 may be determined to be at a position between the third and fourth antennas 86, 88, as the proximity signal in the respective path 102 between the antennas 86, 88 would have a signal strength reduced to a greater extent than that of paths 104, 106 between the other pairs of antennas. [0049] An association, such as a lookup table, may be preset for each pair of antennas 82-88. The association may correlate signal strength to distance from antenna pair. As such, a stronger proximity signal may indicate that an object is closer to a particular pair of antennas 82-88 and a weaker proximity signal may indicate that the object is further from a particular pair of antennas 82-88. The instructions may be to determine a position of the object based on combining multiple distances from antennas pairs. Moreover, the instructions may be to determine speed or velocity of the object based on changes in determined position.

[0050] For example, a first measurement may determine that all paths 102- 08 have a proximity signal strength of about -30 dBm. The first measurement may be taken to indicate that no object is present near the device 80. A subsequent second measurement may determine signal strengths of -75 dBm in the rightmost path 102, -45 dBm in the middle path 104, and -35 dBm in the leftmost path 106. The second measurement may be taken to indicate the presence of an object near the antennas 86, 88 that define the rightmost path 102 and somewhat further from the antennas 84, 86 that define the middle path 104, due to the relative proportional decreases of signal strength in the paths 102-106. A third measurement may determine signal strengths of -65 dBm in the rightmost path 102, -55 dBm in the middle path 104, and -40 dBm in the leftmost path 106. The third measurement may be taken to indicate movement of the object from the position determined by the second measurement to a position closer to the antennas 84, 86 that define the middle path 104. When time of measurement is tracked, speed or velocity of the object may be computed.

[0051] Rapid changes in signal strength in any number of paths 102-104 may indicate undetermined movement of an object near the antennas 82-88. Stable signal strength or gradual changes in signal strength in any number of paths 102-104 may indicate a stationary or slow-moving object near the antennas 82-88. Hence, transient or continued presence or absence of an object may be determined. [0052] An association, such as a lookup table, may be preset to determine any number of distributions of signal strength and changes to signal strength to any number of pairs of antennas 82-88. Such an association may be referenced by processor-executable instructions to determine position and movement of an object in the vicinity of the antennas 82-88.

[0053] FIG. 7 shows an example MI O device 120. The device 80 may be provided to a tablet computer, a notebook or laptop computer, a smartphone, or similar. The device 120 may include any of the features or aspects discussed herein.

[0054] The device 120 may include a plurality of data paths 122. Each data path 122 may include a transmitter, a receiver, or both a transmitter and receiver to transmit and/or receive signals for data communications with a wireless network. It should be understood thai a particular data path 122 may be a transmitter, a receiver, or both a transmitter and receiver, depending on the implementation.

[0055] Each data path 122 may include an antenna 24, a radio frequency (RF) circuit 128, and a digital-to-analog converter (DAC) for transmission and/or an analog-to-digiial converter (ADC) for reception, indicated at 128.

[0056] Any number of proximity signal paths may be defined among the plurality of antennas 124, limited only by the number of antennas 124 used.

[0057] The device 120 may include a modulator/demodulator 130, a channel encoder/decoder 132, a transmit buffer 134, and a receive buffer 136. The transmit and receive buffers 134, 136 may be to queue data for transmission and reception, such data being exchanged with another component of the device (not shown), such as a data bus, processor, or the like. The channel encoder/decoder 132 and modulator/demodulator 130 encode and modulate digital data for transmission and decode and demodulate received digital data, according to any suitable channel encoding and modulation methodologies or protocols. [0058] The device 120 includes a processor 150 and memory 152 connected to the processor 150. The processor 150 may be connected to the transmit and receive buffers 134, 136 to communicate signal data with the antennas 124.

[0059] The processor 150 may include a microcontroller, a microprocessor, a processing core, an FPGA, or similar device capable of executing instructions 154 stored in the memory 152, which may include a non-transitory machine- readable storage medium that may include, for example, RAM, ROM, EEPROM, flash memory, and the like encoded with executable instructions 154. The memory 52 may also store a proximity signal 156, which may be described by a waveform, parameters, and the like. Any number of different proximity signals 156 may be stored.

[0060] The instructions 154 are to control a transmitter at a selected data path 122 to emit a proximity signal 156 via a respective antenna 124 and to control a receiver at a different selected data path 122 to receive a loopback proximity signal 158, which is or contains a representation of the emitted proximity signal 156, via a different respective antenna 124. The instructions 154 are further to compare the proximity signal 156 and the loopback proximity signal 158 to determine a presence or absence of a human body in a path between the emitter and receiver antennas 124.

[0061] To emit a proximity signal 156 via a particular data path 122, the instructions 154 may cause the processor 150 to write the proximity signal to the transmit buffer 134 with an indication of a desired path 122 or antenna 124 for emission of the proximity signal. Conversely, to receive a loopback proximity signal 158, the instructions 154 may cause the processor 150 to read a loopback proximity signal 158 from the receive buffer 136.

[0062] Data paths 122 for proximity signal emission and reception may be selected based on a desired proximity sensor path between the respective pair of antennas 124. Any pair or group of antennas 124 may be used with, for example, one antenna 124 emitting the proximity signal 156 and another one or more antennas 124 receiving a loopback proximity signal 158. A one-to-one or one-to-many approach may be implemented by the instructions 154, in which one or more paths between an emitter antenna 124 and one or more receiver antennas 124 are tested for object presence. The resulting loopback signal or signals 158 may be compared to the emitted proximity signal 156 to determine position, change of position, transience, continuance, or other property of the object.

[0063] A proximity sensor path may be defined by a pair of antennas 124 and such a definition may be stored in the memory 152 as a path definition 160 for reference by the instructions 54 when writing to and reading from the buffers 134, 136.

[0064] The instructions 154 may be to reduce a transmit power of an antenna 124 based on a defected presence of a human body in the path, e.g., by reduced signal strength, as defined by a path definition 160. The instructions 154 may be to increase the transmit power of the antenna 124 based on a determination of an absence of the human body in the path, e.g., by expected signal strength. The instructions 154 may be to reduce and increase a transmit power of each antenna 124 of a pair of antennas associated with a path definition 160 based on the presence or absence of the human body in the path, even if only one of the antennas was controlled to emit a proximity signal.

[0065] FIG. 8 shows a flowchart of another example method. The method may be performed by any of the devices discussed herein and may be performed continually during operation of a device. The method may be implemented by processor-executable instructions. The method starts at block 170.

[0066] At block 72, a proximity signal is emitted by an antenna and a representation of the proximity signal is received at another antenna of the same device. Any of the other methods described herein may be used to implement block 172. A characteristic of the received proximity signal is analyzed to determine whether an object is present or absent in a transient sense, at block 174. For example, a received proximity signal of decreased but rapidly changing RSSI may indicate that an object, such as a human hand, is moving into or out of range of the device. Transmitter power control may be avoided for merely transient changes in object presence or absence. If transience is not detected, then the method ends at block 178. The method may be then restarted,

[0067] If transience is determined at block 174, then a proximity signal is emitted and a representation of the proximity signal is received, at block 178. That is, transient presence or absence of the object may be used to trigger monitoring for continued presence or absence, at block 180. The same proximity signal and the same antennas may be used as in transient detection. However, it is contemplated that different proximity signals and different antennas may be used for transient and continued detection. Any of the other methods described herein may be used to implement block 178.

[0068] A received proximity signal of decreased and gradually changing or unchanging RSSI may indicate that an object is stationary at the device. For example, a hand may be grasping the device or the device may be held to a user's ear. Conversely, a received proximity signal of nominal and gradually changing or unchanging RSSI may indicate that a previously present object has left the vicinity of the device. A preset duration may be referenced to determine whether a stable RSSI has occurred for sufficient time to determine continued presence or absence of the object and trigger transmit power control, if continued presence or absence is not detected, then the method returns to block 172 to check for transience.

[0089] If a continued signal is determined at block 180, then transmit power control is performed for any of the antennas used to emit or receive the proximity signal, at block 182. Transmit power may be backed off if the continued signal indicates continued presence of an object. Conversely, transmit power may be restored if the continued signal indicates continued absence of an object. [0070] FIG. 9 shows an example data structure 200 that may be used to store associations of antennas, signal characteristic conditions, and transmit powers.

[0071] Antenna identifiers 202 for emission of a proximity signal may be associated with antenna identifiers 204 for reception of a loopback proximity signal. This may establish definitions of paths that are to be tested for object proximity. The same antenna may be identified as both an emitter antenna and a receiver antenna.

[0072] Emitter and receiver antenna identifiers 202, 204 may be associated with signal characteristic conditions 208, such as RSSi thresholds indicative of nominal/expected signal strength and decreased signal strength. Any number and type of signal characteristic conditions 206 may be associated with a given path definition set by a unique pair of emitter antenna identifier 202 and receiver antenna identifier 204. For example, multiple RSSi thresholds may be used for multiple levels of transmit power back off. Signal characteristic conditions 206 may be expressed as values, value ranges, equations, inequalities, functions, and the like.

[0073] A signal characteristic condition 206 may indicate rate of change for a characteristic. For example, this may be used to determine whether or how fast an object is moving or this may be used to distinguish between transient and continued object detection.

[0074] Transmit powers 208 may be associated with emitter and receiver antenna identifiers 202, 204 and signal characteristics 206, such that a transmit power for at least one of the emitter and receiver antennas for a path may be selected if the condition set in a respective signal characteristic condition 206 is met.

[0075] The example data structure 200 may be used to establish an association, such as a lookup table, for use with the devices and methods discussed elsewhere herein. [0076] A locus of antenna conditions may be established for the expected service of a device. The iocus, as defined by identifiers 202, 204 and conditions 206, may map to transmit powers, so that antenna power may be looked up for any condition of any number of antennas.

[0077] It should be apparent from the above that a dedicated proximity sensor may be omitted from a device when using antennas as active proximity sensors, as discussed herein. Device complexity may be reduced. Further, if may be possible to control transmit power of each antenna independently, so that object presence at one antenna need not limit transmit power of a physically distant antenna at the same device.

[0078] It should be recognized that features and aspects of the various examples provided above can be combined into further examples that also fall within the scope of the present disclosure, in addition, the figures are not to scale and may have size and shape exaggerated for illustrative purposes.

Claims

1. A device comprising: a plurality of antennas to transmit and receive data with a wireless network, the plurality of antennas including a first antenna and a second antenna; and a processor connected to the plurality of antennas, the processor to execute instructions, the instructions to control the first antenna to emit a proximity signal, control the second antenna to receive a representation of the proximity signal, and determine a presence of an object in a path between the first antenna and the second antenna based on the representation of the proximity signal.

2. The device of claim 1 , wherein the instructions are to control a transmit power of an antenna of the plurality of antennas during data transmission to the wireless network based on the representation of the proximity signal.

3. The device of claim 1 , wherein the instructions are to control the first antenna to emit the proximity signal and control the second antenna to receive the representation of the proximity signal intermittently between data

communications with the wireless network.

4. The device of claim 1 , wherein the instructions are to determine a difference in signal strength between the proximity signal and the representation of the proximity signal and determine the presence of the object in the path between the first antenna and the second antenna based on the difference in signal strength.

5. The device of claim 1 , wherein the instructions are to determine a triggering presence and a continued presence of the object in the path between the first antenna and the second antenna based on the representation of the proximity signal, wherein the instructions are to determine the continued presence in response to determining the triggering presence.

6. The device of claim 5, wherein the instructions are to control a transmit power of an antenna of the plurality of antennas during data transmission to the wireless network when detecting the continued presence.

7. The device of claim 1 , wherein the instructions are to control a third antenna of the plurality of antennas to receive an additional representation of the proximity signal, and to determine the presence of the object in a path between the first antenna and the second antenna or in a path between the first antenna and the third antenna based on the representation and the additional representation of the proximity signal.

8. A device comprising: a transmitter; a receiver; a plurality of antennas; and a processor to control the transmitter to emit a proximity signal and to control the receiver to receive a ioopback proximity signal to determine a presence of a human body in a path among the plurality of antennas.

9. The device of claim 8, wherein the processor is to associate an antenna of the plurality of antennas with the path and to reduce a transmit power of the antenna based on the presence of the human body in the path. 0. The device of claim 9, wherein the processor is to increase a transmit power of the antenna in response to a determination of an absence of the human body in the path. 1. The device of claim 8, wherein the processor is to associate a pair of antennas of the plurality of antennas with the path, the pair of antennas including an antenna to emit the proximity signal and an antenna to receive the proximity signal, the processor further to reduce a transmit power of each antenna of the pair of antennas based on the presence of the human body in the path.

12. The device of claim 8, wherein the processor is to analyze the loopback proximity signal to determine transient presence and continued presence of a human body in the path, and wherein the processor is to reduce a transmit power of an antenna of the plurality of antennas when determining the continued presence.

13. A method comprising: emitting a signal from a first antenna of a device; receiving the signal at a second antenna of the device; determining a characteristic of the signal received at the second antenna; comparing the characteristic of the signal received at the second antenna with a parameter of the signal emitted from the first antenna; and determining a presence of an object in a path between the first antenna and the second antenna based on the comparing.

14. The method of claim 13, further comprising reducing a transmit power of the first antenna in response to determining the presence of the object in the path.

15. The method of claim 13, wherein the emitting and receiving are performed intermittently between transmitting and receiving data signals between the first and second antennas and a wireless network.