PATENT DOCUMENT

Publication Number: US-9791490-B2
Application Number: US-201414299844-A
Country: US
Kind Code: B2

Title: Electronic device having coupler for tapping antenna signals

Abstract:
An electronic device may be provided with wireless circuitry. Control circuitry may be used to adjust transmit power levels for wireless signals, may be used to tune antennas, and may be used to adjust other settings for the wireless circuitry. The electronic device may have a coupler interposed between an antenna and wireless transceiver circuitry. The coupler and a receiver within the transceiver circuitry may be used to make measurements on tapped antenna signals such as transmitted signals and signals reflected from the antenna. By analyzing the tapped antenna signals, S-parameter phase and magnitude information may be gathered that provides insight into whether the electronic device is operating properly and whether an external object is adjacent to the antenna. If an external object is present, the electronic device may limit wireless transmit power and may adjust tunable components in the antenna to compensate for detuning from the external object.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 an antenna; 
 wireless radio-frequency transceiver circuitry that transmits radio-frequency signals at a transmit power level through the antenna; 
 a coupler interposed in a path between the wireless radio-frequency transceiver circuitry and the antenna that taps, from the path, the radio-frequency signals transmitted by the wireless radio-frequency transceiver circuitry; 
 a tapped signal path that carries the tapped radio-frequency signals from the coupler; 
 a receiver in the wireless radio-frequency transceiver circuitry that receives the tapped radio-frequency signals from the tapped signal path and that measures the tapped radio-frequency signals; and 
 a processor that processes the tapped radio-frequency signals to produce S-parameter phase and magnitude information, wherein the coupler comprises switching circuitry and the processor is configured to direct the switching circuitry to route the tapped radio-frequency signals to the tapped signal path. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the radio-frequency signals transmitted by the wireless radio-frequency transceiver circuitry reflect from the antenna, and the processor is configured to direct the switching circuitry to route a tapped version of the reflected transmitted radio-frequency signals to the tapped signal path. 
     
     
       3. The electronic device defined in  claim 2  wherein the switching circuitry comprises a first switch and a second switch, and the first and second switches are controlled by the processor. 
     
     
       4. The electronic device defined in  claim 3  wherein the first switch has a first terminal coupled to the tapped signal path, a second terminal coupled to a first ground termination, and a third terminal that receives the tapped version of the reflected transmitted radio-frequency signals. 
     
     
       5. The electronic device defined in  claim 4  wherein the second switch has a first terminal coupled to the tapped signal path, a second terminal coupled to a second ground termination, and a third terminal that receives the tapped radio-frequency signals. 
     
     
       6. The electronic device defined in  claim 5  further comprising a double-pole-double throw switch interposed between the antenna and the coupler. 
     
     
       7. The electronic device defined in  claim 6  wherein the processor sets a maximum level for the transmit power level based on the phase and magnitude information. 
     
     
       8. The electronic device defined in  claim 7  wherein the antenna comprises tunable components, and the processor adjusts the tunable components to tune the antenna based on the phase and magnitude information. 
     
     
       9. The electronic device defined in  claim 1  wherein the antenna is detuned due to an external object in the vicinity of the antenna, the antenna comprises tunable components, and the processor adjusts the tunable components based on the phase and magnitude information to compensate for the detuning due to the external object. 
     
     
       10. The electronic device defined in  claim 2 , wherein the processor is configured to generate the S-parameter phase and magnitude information based on the tapped radio-frequency signals transmitted by the wireless radio-frequency transceiver circuitry and based on the tapped version of the reflected transmitted radio-frequency signals. 
     
     
       11. The electronic device defined in  claim 10 , wherein the S-parameter phase and magnitude information comprises an S-parameter value computed by the processor as a logarithm of the tapped version of the reflected transmitted radio-frequency signals divided by the tapped radio-frequency signals transmitted by the wireless radio-frequency transceiver circuitry. 
     
     
       12. The electronic device defined in  claim 3 , wherein the first switch is configured to route the tapped version of the reflected transmitted radio-frequency signals to the tapped signal path and the second switch is configured to route the tapped radio-frequency signals transmitted by the wireless radio-frequency transceiver circuitry to the tapped signal path. 
     
     
       13. The electronic device defined in  claim 1 , wherein the processor comprises a baseband processor that generates the S-parameter phase and magnitude information based on the tapped radio-frequency signals carried by the tapped antenna path. 
     
     
       14. The electronic device defined in  claim 5 , wherein the first switch is configured to short the second terminal of the first switch to the third terminal of the first switch while the second switch shorts the first terminal of the second switch to the third terminal of the second switch. 
     
     
       15. The electronic device defined in  claim 14 , wherein the second switch is configured to short the second terminal of the second switch to the third terminal of the second switch while the first switch shorts the third terminal of the first switch to the first terminal of the first switch. 
     
     
       16. The electronic device defined in  claim 2 , wherein the processor comprises a baseband processor, the electronic device further comprising:
 an additional receiver in the wireless radio-frequency transceiver circuitry; 
 a duplexer having a first terminal coupled to the antenna and having second and third terminals; and 
 an adjustable switch having a first input coupled to the tapped signal path, a second input coupled to the second terminal of the duplexer, and an output coupled to the additional receiver, wherein the adjustable switch is controlled using a control signal to selectively couple one of the duplexer and the tapped signal path to the additional receiver. 
 
     
     
       17. The electronic device defined in  claim 16 , further comprising:
 a transmitter in the wireless radio-frequency transceiver circuitry; 
 an amplifier interposed between the transmitter and the third terminal of the duplexer; and 
 additional switching circuitry coupled between the first terminal of the duplexer and the antenna, wherein the coupler is interposed between the additional switching circuitry and the duplexer. 
 
     
     
       18. The electronic device defined in  claim 17 , further comprising:
 an additional antenna; and 
 a third receiver in the wireless radio-frequency transceiver circuitry, wherein the additional switching circuitry has first, second, third, and fourth terminals, the first terminal of the additional switching circuitry is coupled to the first terminal of the duplexer through the coupler, the second terminal of the additional switching circuitry is coupled to the third transceiver, the third terminal of the additional switching circuitry is coupled to the antenna, and the fourth terminal of the additional switching circuitry is coupled to the additional antenna. 
 
     
     
       19. The electronic device defined in  claim 2 , wherein the antenna comprises antenna tuning circuitry, and the processor is configured to:
 reduce the transmit power level in response to identifying, in the S-parameter phase and magnitude information, a first amount of magnitude mismatch and a first amount of phase mismatch between the tapped version of the reflected transmitted radio-frequency signals and the tapped radio-frequency signals transmitted by the wireless radio-frequency transceiver circuitry; and 
 reduce the transmit power level and adjust the antenna tuning circuitry in response to identifying, in the S-parameter phase and magnitude information, a second amount of magnitude mismatch and the first amount of phase mismatch between the tapped version of the reflected transmitted radio-frequency signals and the tapped radio-frequency signals transmitted by the wireless radio-frequency transceiver circuitry, wherein the second amount of magnitude mismatch is greater than the first amount of magnitude mismatch.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with wireless communications circuitry. 
     Electronic devices often include wireless communications circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications. 
     It can be challenging to assemble and operate wireless electronic devices. During assembly, it may be difficult to determine whether assembly operations have been performed correctly. If care is not taken, antennas may not be properly interconnected with other portions of a device. Calibration steps may require the extensive use of test equipment and may take more time than desired. During operation of a wireless device by a user, wireless performance can be affected by changes in the environment of the wireless device. 
     It would therefore be desirable to be able to provide improved ways for characterizing the operation of wireless devices in various operating environments. 
     SUMMARY 
     An electronic device may be provided with wireless circuitry for transmitting and receiving wireless signals. Control circuitry may be used to adjust transmit power levels for the wireless signals, may be used to tune antennas, and may be used to adjust other settings for the wireless circuitry. 
     The electronic device may have one or more antennas. A coupler may be interposed between an antenna and wireless transceiver circuitry. Switching circuitry in the coupler may be used to allow the coupler to sample signals flowing from the transceiver circuitry and the antenna and to sample signals flowing from the antenna to the transceiver circuitry. 
     Using the coupler and using a receiver within the transceiver circuitry, a processor such as a baseband processor integrated circuit may make measurements on tapped antenna signals such as transmitted signals and signals reflected from the antenna. By analyzing the tapped antenna signals, S-parameter phase and magnitude information may be gathered that provides insight into whether the electronic device is operating properly and whether an external object is adjacent to the antenna. If an external object is present, the electronic device may limit wireless transmit power and may adjust tunable components in the antenna to compensate for detuning from the external object. The tapped antenna signals may be used in calibrating the wireless circuitry and may be used as part of a self-test routine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment. 
         FIG. 3  is a diagram of illustrative wireless circuitry in accordance with an embodiment. 
         FIG. 4  is a diagram of an illustrative antenna of the type that may be influenced by the presence of an external object in the vicinity of the antenna in accordance with an embodiment. 
         FIG. 5  is a circuit diagram of illustrative circuitry that may be used to gather tapped antenna signals in accordance with an embodiment. 
         FIG. 6  is a graph in which the magnitude of an S-parameter associated with an antenna port has been plotted as a function of frequency in accordance with an embodiment. 
         FIG. 7  is a graph in which the phase of the S-parameter has been plotted as a function of frequency in accordance with an embodiment. 
         FIG. 8  is a table showing illustrative measured antenna feedback values and associated operating modes for an electronic device in accordance with an embodiment. 
         FIG. 9  is a flow chart of illustrative steps involved in gathering phase and magnitude information for antenna signals in a device and taking appropriate action during operation of the device in accordance with an embodiment. 
         FIG. 10  is a graph showing how tapped antenna signals can be used in calibrating wireless circuitry in accordance with an embodiment. 
         FIG. 11  is a flow chart of illustrative steps involved in using measurements of tapped antenna signals to calibrate wireless circuitry in an electronic device in accordance with an embodiment. 
         FIG. 12  is a flow chart of illustrative steps involved in using measurements of tapped antenna signals to evaluate whether a device is functioning properly in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device such as electronic device  10  of  FIG. 1  may contain wireless circuitry. A coupler may be used to tap into a path between a radio-frequency transceiver and an associated antenna. The output from the tap can be used to measure antenna signals being transmitted to the antenna and antenna signals being reflected from the antenna. Processing circuitry within the electronic device may process the tapped antenna signals to produce phase and magnitude information (e.g., the phase and magnitude of an S-parameter such as S 11 , where network port  1  corresponds to the antenna port for the antenna, the phase and magnitude of antenna impedance, etc.). The phase and magnitude information can be used in evaluating device operation during testing, can be used during calibration operations, and can be used in real-time control of wireless circuitry in a device. 
     Device  10  may contain wireless communications circuitry that operates in long-range communications bands such as cellular telephone bands and wireless circuitry that operates in short-range communications bands such as the 2.4 GHz Bluetooth® band and the 2.4 GHz and 5 GHz WiFi® wireless local area network bands (sometimes referred to as IEEE 802.11 bands or wireless local area network communications bands). Device  10  may also contain wireless communications circuitry for implementing near-field communications, light-based wireless communications, satellite navigation system communications, or other wireless communications. 
     Electronic device  10  may be a computing device such as a laptop 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 wrist-watch 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, equipment that implements the functionality of two or more of these devices, or other electronic equipment. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a cellular telephone, media player, tablet computer, or other portable computing device. Other configurations may be used for device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     In the example of  FIG. 1 , device  10  includes a display such as display  14 . Display  14  has been mounted in a housing such as housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. 
     Display  14  may include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic display pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass or clear plastic. Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button such as button  16 . An opening may also be formed in the display cover layer to accommodate ports such as speaker port  18 . Openings may be formed in housing  12  to form communications ports (e.g., an audio jack port, a digital data port, etc.). 
     A schematic diagram showing illustrative components that may be used in device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may include control circuitry such as storage and processing circuitry  30 . Storage and processing circuitry  30  may include storage such as 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. Processing circuitry in storage and processing circuitry  30  may be used to control the operation of device  10 . This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processor integrated circuits, application specific integrated circuits, etc. 
     Storage and processing circuitry  30  may be used to run software on device  10 , such as 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, storage and processing circuitry  30  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  30  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, MIMO protocols, antenna diversity protocols, etc. 
     Device  10  may include input-output circuitry  44 . Input-output circuitry  44  may include input-output devices  32 . Input-output devices  32  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  32  may include user interface devices, data port devices, and other input-output components. For example, input-output devices may include touch screens, displays without touch sensor capabilities, buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, buttons, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, motion sensors (accelerometers), capacitance sensors, proximity sensors (e.g., a capacitive proximity sensor and/or an infrared proximity sensor), magnetic sensors, connector port sensors that determine whether a connector such as an audio jack and/or digital data connector have been inserted in a connector port in device  10 , a connector port sensor or other sensor that determines whether device  10  is mounted in a dock, other sensors for determining whether device  10  is coupled to an accessory, and other sensors and input-output components. 
     Input-output circuitry  44  may include wireless communications circuitry  34  for communicating wirelessly with external equipment. Wireless communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Wireless communications circuitry  34  may include radio-frequency transceiver circuitry  90  for handling various radio-frequency communications bands. For example, circuitry  34  may include transceiver circuitry  36 ,  38 , and  42 . 
     Transceiver circuitry  36  may be wireless local area network transceiver circuitry that may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and that may handle the 2.4 GHz Bluetooth® communications band. 
     Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in frequency ranges such as a low communications band from 700 to 960 MHz, a midband from 1710 to 2170 MHz, and a high band from 2300 to 2700 MHz or other communications bands between 700 MHz and 2700 MHz or other suitable frequencies (as examples). Circuitry  38  may handle voice data and non-voice data. 
     Wireless communications circuitry  34  can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  may include 60 GHz transceiver circuitry, circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc. 
     Wireless communications circuitry  34  may include satellite navigation system circuitry such as global positioning system (GPS) receiver circuitry  42  for receiving GPS signals at 1575 MHz or for handling other satellite positioning data. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communications circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable antenna types. 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, hybrids of these designs, etc. If desired, one or more of antennas  40  may be cavity-backed antennas. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. 
     Transmission line paths may be used to couple antenna structures  40  to transceiver circuitry  90 . Transmission lines in device  10  may include coaxial cable paths, 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. Filter circuitry, switching circuitry, impedance matching circuitry, and other circuitry may be interposed within the transmission lines, if desired. 
     Device  10  may contain multiple antennas  40 . One or more of the antennas may be blocked by a user&#39;s body or other external object while one or more other antennas are not blocked. If desired, control circuitry  30  may be used to select an optimum antenna to use in device  10  in real time (e.g., an optimum antenna to transmit signals, etc.). Control circuitry  30  may, for example, make an antenna selection based on information on received signal strength, based on sensor data (e.g., information from a proximity sensor indicating which of multiple antennas may be blocked by an external object), based on tapped antenna signals from a coupler (e.g., phase and/or magnitude information), or based on other information. 
     As shown in  FIG. 3 , transceiver circuitry  90  in wireless circuitry  34  may be coupled to antenna structures  40  using paths such as path  92 . Wireless circuitry  34  may be coupled to control circuitry  30 . Control circuitry  30  may be coupled to input-output devices  32 . Input-output devices  32  may supply output from device  10  and may receive input from sources that are external to device  10 . 
     To provide antenna structures  40  with the ability to cover communications frequencies of interest, antenna structures  40  may be provided with circuitry such as filter circuitry (e.g., one or more passive filters and/or one or more tunable filter circuits). Discrete components such as capacitors, inductors, and resistors may be incorporated into the filter circuitry. Capacitive structures, inductive structures, and resistive structures may also be formed from patterned metal structures (e.g., part of an antenna). If desired, antenna structures  40  may be provided with adjustable circuits such as tunable components  102  to tune antennas over communications bands of interest. Tunable components  102  may include tunable inductors, tunable capacitors, or other tunable components. Tunable components such as these may be based on switches and networks of fixed components, distributed metal structures that produce associated distributed capacitances and inductances, variable solid state devices for producing variable capacitance and inductance values, tunable filters, or other suitable tunable structures. During operation of device  10 , control circuitry  30  may issue control signals on one or more paths such as path  88  that adjust inductance values, capacitance values, or other parameters associated with tunable components  102 , thereby tuning antenna structures  40  to cover desired communications bands. 
     Path  92  may include one or more transmission lines. As an example, signal path  92  of  FIG. 3  may be a transmission line having a positive signal conductor such as line  94  and a ground signal conductor such as line  96 . Lines  94  and  96  may form parts of a coaxial cable or a microstrip transmission line (as examples). A matching network formed from components such as inductors, resistors, and capacitors may be used in matching the impedance of antenna structures  40  to the impedance of transmission line  92 . Matching network components may be provided as discrete components (e.g., surface mount technology components) or may be formed from housing structures, printed circuit board structures, traces on plastic supports, etc. Components such as these may also be used in forming filter circuitry in antenna structures  40 . 
     Transmission line  92  may be coupled to antenna feed structures associated with antenna structures  40 . As an example, antenna structures  40  may form an inverted-F antenna, a slot antenna, a hybrid inverted-F slot antenna or other antenna having an antenna feed with a positive antenna feed terminal such as terminal  98  and a ground antenna feed terminal such as ground antenna feed terminal  100 . Positive transmission line conductor  94  may be coupled to positive antenna feed terminal  98  and ground transmission line conductor  96  may be coupled to ground antenna feed terminal  92 . Other types of antenna feed arrangements may be used if desired. The illustrative feeding configuration of  FIG. 3  is merely illustrative. 
       FIG. 4  is a diagram of illustrative inverted-F antenna structures that may be used in implementing antenna  40  for device  10 . Inverted-F antenna  40  of  FIG. 4  has antenna resonating element  106  and antenna ground (ground plane)  104 . Antenna resonating element  106  may have a main resonating element arm such as arm  108 . The length of arm  108  may be selected so that antenna  40  resonates at desired operating frequencies. For example, if the length of arm  108  may be a quarter of a wavelength at a desired operating frequency for antenna  40 . Antenna  40  may also exhibit resonances at harmonic frequencies. 
     Main resonating element arm  108  may be coupled to ground  104  by return path  110 . Tunable component(s)  102  (e.g., an adjustable inductor, an adjustable capacitor, and/or other adjustable component) may be interposed in path  110  or may be incorporated elsewhere in antenna  40 . Antenna feed  112  may include positive antenna feed terminal  98  and ground antenna feed terminal  100  and may run parallel to return path  110  between arm  108  and ground  104 . If desired, inverted-F antennas such as illustrative antenna  40  of  FIG. 4  may have more than one resonating arm branch (e.g., to create multiple frequency resonances to support operations in multiple communications bands) or may have other antenna structures (e.g., parasitic antenna resonating elements, tunable components to support antenna tuning, etc.). 
     Antennas such as antenna  40  of  FIG. 4  may be affected by the presence of nearby objects. For example, an antenna may exhibit an expected frequency response when device  10  is operated in free space in the absence of nearby external objects such as external object  114 , but may exhibit a different frequency response when device  10  is operated in the presence of external object  114 . The magnitude of the distance between external object  114  and antenna  40  may also influence antenna performance. 
     External objects such as object  114  may include a user&#39;s body (e.g., a user&#39;s head, a user&#39;s leg, or other user body part), may include a table or other surface on which device  10  is resting, may include dielectric objects, may include conductive objects, and/or may include other objects that affect wireless performance (e.g., by loading antenna  40  in device  10  and thereby affecting antenna impedance for antenna  40 ). 
     When an external object such as object  114  is brought into the vicinity of antenna  40  (e.g., when object  114  is within 10 cm of antenna  40 , when object  114  is within 1 cm of antenna  40 , when object  114  is within 1 mm of antenna  40 , or when distance D between antenna  40  and object  114  has other suitable values), antenna  40  may exhibit an altered frequency response (e.g., antenna  40  may be detuned because the impedance of the antenna has been changed due to loading from object  114 ). Using phase and magnitude information from tapped antenna signals, device  10  (e.g., processor  30 ) may control the operation of wireless circuitry  34  accordingly. For example, when it is determined from tapped antenna signals that antenna  40  has been detuned due to the presence of external object  114 , tunable components  102  may be adjusted to compensate for the detuning. As another example, if it is determined that an external object such as a user&#39;s body is present, the maximum transmit power that is used by device  10  in transmitting signals through antenna  40  can be reduced. 
       FIG. 5  is a diagram of illustrative wireless circuitry based on multiple antennas  40 . As shown in  FIG. 5 , antennas  40  may include a first antenna such as antenna  40 A and a second antenna such as antenna  40 B. Antennas  40  may be coupled to transceiver circuitry  90  and other circuitry such as baseband processor  132 . Transceiver circuitry  90  may include receivers and/or transmitters. For example, transceiver circuitry  90  may include a first transceiver such as transceiver  90 A (e.g., receiver  128  and transmitter  130 , which may be coupled to path  124  via duplexer  152  or other circuitry), a second transceiver such as transceiver  90 B (e.g., a receiver), and a third transceiver such as transceiver  90 C (e.g., a receiver). 
     Circuitry  144  may be interposed between path  124  and transceiver circuitry  90 . Paths  124  and path  126  may be coupled to antennas  40 A and  40 B using switching circuitry  120 . Switching circuitry  120  may be, for example, a double-pole-double-throw switch that is controlled by control signals at switch control input  122 . In a first state, switch  120  couples antenna  40 A to path  124  and couples antenna  40 B to path  126 . In a second state, switch  120  couples antenna  40 B to path  124  and couples antenna  40 A to path  126 . 
     Antennas  40 A and  40 B may be located at opposing upper and lower ends of electronic device  10  and housing  12  of  FIG. 1  or may be located elsewhere in device  10 . Control circuitry in device  10  may use received signal strength information, sensor information, and/or antenna feedback information (e.g., antenna impedance information) to determine whether switch  120  should be placed in the first state or the second state. For example, the lower antenna in device  10  may be used as a primary antenna to transmit and receive signals while the upper antenna in device  10  is used as a secondary antenna that only receives signals. When received signal strength with the lower antenna drops below a threshold amount or when other criteria are satisfied, the state of switch  120  may be changed so that the upper antenna is switched into use in place of the lower antenna (as an example). 
     Circuitry  144  may include coupler  136 . Coupler  136  may be used to tap antenna signals flowing between transceiver circuitry  90  and antennas  40 . Coupler  136  has internal terminals A and B and has external terminals C and D. Switching circuitry in coupler  136  can direct tapped signals to terminals C and D. Terminals C and D are coupled to tapped antenna signal path  162 . Path  162  may be coupled to a receiver in transceiver circuitry  90 , so that tapped antenna signals can be measured and processed. In the example of  FIG. 5 , receiver  90 C is being used to receive signals on path  162 . If desired, switching circuitry (see, e.g., optional switch  180 ) or other circuitry may be used to route signals from path  162  to other receivers in transceiver circuitry  90  (see, e.g., receiver  128  and receiver  90 B). The use of a dedicated receiver such as receiver  90 C for receiving tapped antenna signals from path  162  is merely illustrative. 
     Using circuitry  144 , antenna impedance information for the currently active antenna can be gathered. The impedance information may be gathered by gathering S-parameter information such as the phase and magnitude of S 11  (where network port  1  in this example is associated with the currently active antenna in antennas  40 ). For example, if antenna  40 A is the currently active antenna associated with transmitter  130 , transmitter  130  may transmit antenna signals to antenna  40 A using output path  150 , power amplifier  142 , duplexer  152 , and path  154 . Coupler  136  may be used to route a tapped version of the transmitted signals and a tapped version of reflected signals from antenna  40 A to path  162 . Receiver  90 C and baseband processor  132  can process these tapped signals to produce information on the phase of S 11  at output  170  and the magnitude of S 11  at output  172 . Processor  132  may also retain this information internally. Processor  132  and/or other processing circuitry  30  in device  10  may take appropriate action based on the signal values at outputs  170  and/or  172  and may, if desired, further process these signal values (e.g., to produce real and imaginary antenna impedance information, etc.). 
     As shown in  FIG. 5 , coupler  136  may have switching circuitry such as switches  156  and  158 . Control signals from baseband processor  132  (e.g., control signals from control output  138 ) or other control signals may be supplied to control path  160  to adjust the states of switches  156  and  158 . Switch  156  may be directed to couple internal coupler terminal A to coupler output terminal C or to termination  164  (e.g., a 50 ohm ground termination). Switch  158  may be directed to couple internal coupler terminal B to coupler output terminal D or to termination  166  (e.g., a 50 ohm ground termination). When it is desired to measure transmitted antenna signals flowing from path  154  to path  124  through coupler  136 , switch  158  is directed to short terminal B to terminal D while switch  156  connects terminal A to termination  164 , so that receiver  90 C measures a tapped version of the transmitted signal on path  162 . When it is desired to measure received antenna signals flowing from path  124  to path  154  through coupler  136  (e.g., reflected signals from antenna  40 A when antenna  40 A is the active antenna), switch  156  is directed to short terminal A to terminal C while switch  158  connects terminal B to termination  166 , so that receiver  90 C measures the tapped version of the reflected signal on path  162 . The magnitude of S 11  is given by the log of the reflected signal divided by the forward (transmitted) signal and is supplied by processor  132  to output  172 . The phase of S 11  is supplied to output  170 . 
     Baseband processor  132  may be an integrated circuit that is coupled to processing circuitry in device  10  via paths such as path  134 . During normal operation, baseband processor  132  receives data to be transmitted from circuits in control circuitry  30  via path  134  and provides received data to circuits in control circuitry  30  via path  134 . During antenna impedance data gathering operations, baseband processor  132  can use transceiver circuitry  90  and the other circuitry of  FIG. 5  to extract real and imaginary antenna impedance information for antennas  40 . For example, baseband processor  132  can use transceiver circuitry  90  and coupler  136  to gather phase and magnitude information for tapped antenna signals (e.g., S 11  phase and magnitude information). Based on this information and other information (e.g., received signal strength information, sensor data from a proximity sensor and other sensors, etc.), baseband processor  132  or other control circuitry in device may generate control signals (see, e.g., control signal output  138  of  FIG. 5 ). The control signals may be used in tuning antenna  40 A and/or  40 B (e.g., by adjusting tunable components  102 ), may be used in switching one or more antennas into use (e.g., by supplying a control signal to a switch control input such as input  122  of double-pole-double-throw antenna switch  120 ), may be used in controlling output power from a transmitter in transceiver circuitry  90  such as transmitter  130 , may be used in controlling output power by adjusting power amplifier gain with control signals applied to control input  140  of power amplifier  142 , or may otherwise be used in controlling the operation of device  10 . Information on paths  170  and  172  may also be used in taking other actions (e.g., issuing alerts, making pass/fail decisions during testing as part of a manufacturing process or in-store diagnostics routine being run on device  10 , etc.). 
     Antenna impedance information gathered using coupler  136  and the other circuitry of  FIG. 5  may be used to perform in-factory diagnostics, to perform in-store diagnostics (service center diagnostics), to calibrate the transmitter circuitry and/or other wireless circuitry in device  10 , and to control the operation of device  10  in real time. 
     Consider, as an example, in-factory or in-store diagnostics. The proper functioning of the wireless circuitry of device  10  can be verified using antenna impedance data. If an antenna connector, a transmission line for an antenna, a circuit that is coupled to an antenna, or other circuit associated with handling antenna signals in device  10  is faulty, the antenna impedance data gathered using coupler  136  will be affected. Accordingly, phase and magnitude information of the type produced on outputs  170  and  172  may be used to check whether device  10  is functioning properly (e.g., whether cables and other signal paths are properly attached to each other within housing  12 , whether transceiver circuitry and switches are functioning properly, whether antenna structures have been damaged or are operating satisfactorily, etc.). 
     As another example, consider real time operation of device  10 . As described in connection with  FIG. 4 , the impedance of antenna  40  can be influenced by the operating environment of antenna  40 . As an example, antenna  40  may function differently when operated in the absence of external objects than when operated in the vicinity of external object  114 . Moreover, different types of external objects  114  (e.g., different parts of a user&#39;s body, inanimate objects, conductive structures, etc.) may affect antenna operation differently. To ensure that antenna  40  operates as desired, real time antenna impedance data (and/or related information such as the magnitude and phase of S 11  at outputs  170  and  172 ) can be evaluated by processor  132  or other processing circuitry in device  10 . 
       FIGS. 6 and 7  are graphs of illustrative S 11  magnitude and phase information from outputs  172  and  170 , respectively. The data in these graphs illustrates the type of information that may be gathered when operating wireless circuitry  34  under various different operating conditions. In this example, curve  200  of  FIG. 6  represents the magnitude of S 11  (output  172 ) during normal operation of antenna  40  in the absence of external object  114 . Curve  206  represents the phase of S 11  (output  170 ) during normal operation of antenna  40  in the absence of external object  144 . When object  114  (e.g., a part of a user&#39;s body) is at a first distance D (e.g., a distance of 5 cm) from antenna  40 , the operation of antenna  40  is detuned due to loading from object  114 , as shown by curve  202  of  FIG. 6  and curve  208  of  FIG. 7 . In this case output  172  changes from M 1  (normal operation; antenna is unloaded) to M 2  (slightly loaded) and output  170  changes from PH 1  (normal operation; antenna is unloaded) to PH 2  (slightly loaded). When object  114  is at a second distance D (e.g., a distance of 1 mm), output  172  changes from M 2  (slightly loaded) to M 3  (heavily loaded) and output  170  changes from PH 2  (slightly loaded) to PH 3  (heavily loaded). 
     As shown in  FIGS. 6 and 7 , phase data tends to be more sensitive to loading from external objects than magnitude data, so PH 2  changes significantly from PH 1 , whereas M 2  does not change significantly from M 1 . Under heavy loading, however, M 3  changes significantly from M 2 . By analyzing both phase and magnitude data, device  10  can accurately evaluate the current operating environment of device  10  (e.g., the loading of antenna  40 ) and can take corrective actions. Under slight loading conditions, antenna  40  may be only slightly detuned (see, e.g., the resonance of curve  202  in  FIG. 6 , which is shifted to a frequency that is only slightly below normal operating frequency band f 1  of curve  200 ), so no corrective tuning of antenna  40  may be needed. Under heavy loading conditions, however, antenna  40  may become significantly detuned (as shown by curve  204  of  FIG. 6 ), thereby requiring compensating tuning of tunable elements  102  in antenna  40 . Once elements  102  are tuned, the frequency response to the antenna will return to normal curve  200 . 
     In general, processing circuitry such as baseband processor  132  or other processing circuitry in device  10  may determine how severely antenna  40  has been affected by external object  114  and/or may deduce the nature of external object  114  using phase and magnitude information (e.g., to determine distance D of object  114  and/or to determine what part of a user&#39;s body is present in the vicinity of antenna  40  based on the loading characteristics of that body part and/or to determine whether external object  114  is associated with a user&#39;s body or is associated instead with an inanimate object such as a table). Sensor data (e.g., accelerometer data, audio data, proximity sensor data, etc.) and data on the current operating mode of device  10  (e.g., whether or not the ear speaker of device  10  is being actively used) may also be processed to provide additional information on the current operating environment of device  10  and the performance of antenna  40 . Based on this information, the processing circuitry of device  10  can take suitable action. For example, the processing circuitry of device  10  may adjust antenna tuning, may set appropriate maximum transmit power values to establish appropriate transmit power limits, may perform antenna switching, etc. 
       FIG. 8  is a table illustrating how device  10  may operate under three different operating scenarios. In the scenario illustrated in the first row of the table of  FIG. 8 , the phase and magnitude data from outputs  170  and  174  is normal, so device  10  operates antenna  40  and transceiver circuitry  90  normally. The tuning of tunable components  102  is set to its normal state and the transmit power from transmitter  130  and power amplifier  142  is not restricted. Transmit power may be increased or decreased based on received instructions (transmit power commands) from a wireless base station and need not be limited due to the presence of an external object in the vicinity of device  10 . 
     In the scenario illustrated in the second row of the table of  FIG. 8 , the measured phase signal on output  170  has changed from PH 1  to PH 2  and the measured magnitude signal on output  172  has changed from M 1  to M 2 . Under these conditions (large phase mismatch and small magnitude mismatch), processor  132  can conclude that external object  114  is within a first distance D 1  of antenna  40 . As a result, the processor can reduce the maximum permitted output power from antenna  40  to ensure that regulatory limits on transmitted power are satisfied. Antenna  40  will not be significantly detuned by the presence of object  114 , so no tuning adjustments are made to antenna  40 . 
     In the scenario illustrated in the third row of the table of  FIG. 8 , both the phase and magnitude are significantly mismatched, so device  10  can conclude that external object  114  is within a second distance D 2  that is smaller than D 1 . Device  10  can also conclude that antenna  40  will be detuned significantly from its desired operating state unless compensating adjustments are made. As a result, processor  132  may limit the maximum transmit power from antenna  40  (e.g., a maximum power level may be established that is lower than the maximum power permitted during operation in the scenario of the second row of the  FIG. 8  table) and may adjust tunable antenna components  102  to compensate antenna  40  for the antenna detuning that would otherwise be experienced by antenna  40 . As an example, if detuning results in a lowered resonant frequency for antenna  40  as illustrated by detuned curve  204  of  FIG. 6 , components  102  may be adjusted to raise the resonant frequency of antenna  40  back to the position of curve  200  (e.g., by adjusting an adjustable inductor in return path  110  to a lower inductor value). 
     Illustrative steps involved in performing these types of antenna evaluation and wireless circuit adjustment operations are shown in  FIG. 9 . During operation of device  10 , a user may use wireless circuitry  34  to transmit and receive wireless signals. Using coupler  136 , tapped antenna signals may be gathered. This allows processor  132  to produce real and imaginary impedance information (and/or related information such as S 11  phase and magnitude data) for the currently active antenna (step  212 ). During the operations of step  214 , the gathered antenna data can be evaluated and suitable actions taken by device  10  in real time. For example, maximum transmit powers may be adjusted and antenna  40  may be tuned, as described in connection with  FIG. 8 . Processing may then loop back to step  212 , as illustrated by line  216 . 
       FIG. 10  is a graph showing how gathered tapped antenna data (e.g., S 11  magnitude information in the example of  FIG. 10 ) may be used during calibration operations and diagnostic operations. In the  FIG. 10  example, curve  218  corresponds to a normal expected magnitude signal from output  172  covering a range of operating frequencies including low band frequencies around frequency f 1  and high band frequencies. If wireless circuitry  34  contains a fault (e.g., a disconnected connector, a crack in an antenna trace or signal line trace, a loose solder joint in an antenna or antenna signal path, or other antenna-related failure that arises during manufacturing or during normal use of device  10 ), curve  218  will be affected and may exhibit a characteristic such as curve  220 . During assembly of device  10  and/or during a diagnostics routine run by device  10  in a store or other service facility associated with the manufacturer of device  10  when device  10  is returned by the user for servicing, the presence of an abnormal antenna response curve such as curve  220  may be detected by processor  132  and appropriate action taken. 
     The graph of  FIG. 10  shows how antenna measurements made using coupler  136  and processor  132  may also be used during calibration operations. As indicated by illustrative calibration measurements  222 , wireless circuitry  24  may be calibrated by using coupler  136  to make a series of measurements at different frequencies and transmit powers. The results of these measurements may be gathered using coupler  136  and processor  132  (e.g., as S 11  magnitude information on output  172 ). To ensure calibration accuracy, coupler  136  can first be calibrated using an external power meter (e.g., a power meter plugged into a port in path  124  or other suitable antenna signal path). Following calibration of coupler  136 , processor  132  can direct transmitter  130  to transmit signals over a range of output power levels (e.g., in 2 dB power increments) and output frequencies. At each different set of transmit power and frequency settings, a different corresponding tapped antenna signal can be captured using coupler  136 . Although the entire calibration process may be time consuming (e.g., taking many minutes or even hours to complete), no external equipment (e.g., no external vector network analyzer) need be used to calibrate device  10  across all frequencies and power levels of interest. As a result of this ability to self-calibrate devices  10 , numerous devices  10  can be calibrated in a factory in parallel without requiring the use of costly and complex test equipment. 
       FIG. 11  is a flow chart of illustrative steps involved in calibrating device  10  in this way. At step  224 , wireless circuit components for circuitry  34  may be assembled. For example, cables and other transmission line structures may be plugged into connectors, antenna structures may be fabricated, and, if desired, some or all of the rest of wireless circuitry  34  and device  10  can be assembled. Assembly operations may be performed at the device level (e.g., device  10  may be fabricated in its entirety) or at the board level (e.g., one or more printed circuits may be populated with antenna components, transceiver components, and other wireless circuitry  34  without completing the fabrication of device  10 ). 
     Following component assembly operations at step  224 , an external power meter may, at step  226 , be attached to an antenna port in device  10  (e.g., a port associated with antenna  40 A). As an example, a power meter probe may be coupled to a connector adjacent to antenna  40 A that momentarily disconnects antenna  40 A while coupling the probe into the signal path between the antenna and transceiver. 
     While the power meter is attached, processor  132  may use transmitter  130  to transmit radio-frequency signals at a particular power level (step  228 ). The power meter captures the power and processor  132  uses coupler  136  to capture a tapped version of the transmitted power. By comparing the tapped signal reading to the power meter reading, coupler  136  may be calibrated. 
     Accordingly, at step  230 , wireless circuitry  34  can be calibrated across numerous different operating frequencies and output power levels as part of a calibration routine that is run at step  230 . As an example, an operator at a factory or other establishment may initiate a calibration routine that runs on processing circuitry  132  or other processing circuitry for device  10 . The calibration routine may systematically alter the transmit frequency and transmit power of transmitter  130  while gathering tapped antenna signals using coupler  136  (e.g., magnitude information and, if desired, phase information). In this way, all desired frequencies may be calibrated (i.e., frequency-dependent variations may be determined) and power-dependent (non-linear) behaviors can be observed. The resulting calibration data for device  10  may be stored in storage in device  10  (see, e.g., storage and processing circuitry  30 ). 
     At step  232 , device  10  can be used by a user to handle wireless communications. During normal operation, transmitter  130  can transmit power at calibrated levels using the calibration information stored in storage and processing circuitry  30 . 
     In some situations, after some or all of device  10  has been assembled (step  224 ), faults may arise that can disrupt wireless operations. As an example, an antenna signal path may not be connected properly during initial device assembly operations or an antenna signal path may become loosened within device  10  during use (e.g., a cable connector or other antenna signal connector may become loose when device  10  is inadvertently dropped by a user).  FIG. 12  is a flow chart of illustrative operations that may be performed to use phase and magnitude data from coupler  136  (e.g., phase signals on line  170  and/or magnitude signals on path  172 ) in running diagnostics on device  10  (whether fully or partly assembled). 
     At step  234  of  FIG. 12 , a data capture routine may be initiated. As an example, a data capture software program may be run on device  10  as part of a manufacturing diagnostic (e.g., a self-test routine initiated when manufacturing personnel select an on-screen option or when a wireless command or wired command is transmitted to device  10 ) or personnel in a service center may select an on-screen option on device  10  or may otherwise initiate a diagnostics routine. 
     At step  236 , as part of the diagnostics routine running on device  10 , processor  132  may use coupler  136  to gather phase and/or magnitude information for antenna  40  (e.g., impedance data). The captured data may reveal that device  10  is operating normally (see, e.g., normal antenna response curve  218 ) or may reveal that device  10  contains a fault (see, e.g., faulty antenna response curve  220 ). 
     At step  238 , processor  132  may evaluate the captured data or, if desired, other circuitry in device  10  or ancillary external processing circuitry may evaluate the captured data. Appropriate action may then be taken based on the analyzed tapped antenna signal data. For example, if it is determined that device  10  is operating properly, processor  132  or other equipment may issue a visual message, an audible alert, or other message for personnel running the diagnostic test to indicate that device  10  has passed diagnostic testing. If it is determined that device  10  contains a fault, personnel associated with the diagnostic test may be informed the device  10  has failed testing and should be repaired, reworked, or discarded. 
     In some situations, diagnostic results will reveal that device  10  is not performing properly (e.g., because antenna characteristic  220  is detected instead of desired antenna characteristic  218 ), but it will not be possible to pinpoint the nature of the problem (e.g., the problem may be due either to a crack in a signal line or a crack in an antenna trace, but only visual inspection will reveal which of these two possible faults is present). 
     In other situations, the diagnostic routine running on device  10  can provide personnel associated with the test with more detailed test results. As an example, the shape of an antenna performance curve that is gathered may show that a particular antenna cable has been disconnected. Whenever device  10  is able to identify what type of problem that has been detected, an alert message may be displayed by control circuitry  30  on display  14  or other output may be provided that informs personnel running the diagnostic test of the nature of the test results. As an example, a message may be displayed on display  14  that contains repair instructions such as “replace wireless transceiver board” or “reconnect loose antenna flex” or that contains other detailed test results. 
     During manufacturing, it may be possible to rework faulty parts. In a repair center environment, a faulty part may require device  10  to be replaced or a more extensive repair may be made (e.g., by replacing a faulty printed circuit). Self-test diagnostic routines may, in general, be run in a factory setting or in a service-center setting or may be run by a user of device  10  (e.g., to determine whether device  10  requires servicing by authorized service personnel). 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20140609
Publication Date: 20171017
Grant Date: 20171017
Priority Date: 20140609
Inventors: PASCOLINI MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "G01R29/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R29/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R29/10", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 54782374