PATENT DOCUMENT

Publication Number: US-9154972-B2
Application Number: US-201313916090-A
Country: US
Kind Code: B2

Title: Methods and apparatus for testing electronic devices with antenna arrays

Abstract:
A wireless electronic device may be provided with antenna structures. The antenna structures may be formed from an antenna ground and an array of antenna resonating elements formed along its periphery. The antenna resonating elements may be formed from metal traces on a dielectric support structure that surrounds the antenna ground. The electronic device may be tested using a test system for detecting the presence of manufacturing/assembly defects. The test system may include an RF tester and a test fixture. The device under test (DUT) may be attached to the test fixture during testing. Multiple test probes arranged along the periphery of the DUT may be used to transmit and receive RF test signals for gathering scattering parameter measurements on the device under test. The scattering parameter measurements may then be compared to predetermined threshold values to determine whether the DUT contains any defects.

Claims:
What is claimed is: 
     
       1. A method for using a test system to test a device under test having a periphery and an array of antennas formed along its periphery, wherein the test system includes a test fixture and a test unit, the method comprising:
 forming a test waveguide structure along the periphery of the device under test by placing the device under test in the test fixture; and 
 while the device under test is placed in the test fixture, generating radio-frequency test signals with the test unit and passing the radio-frequency test signals through the test waveguide structure. 
 
     
     
       2. The method defined in  claim 1 , wherein the array of antennas in the device under test includes more than three antennas formed along the periphery of the device under test, and wherein the test waveguide guide structure overlaps with at least some of the three antennas while the device under test is placed in the test fixture. 
     
     
       3. The method defined in  claim 1 , wherein the device under test is operable in a upright orientation during normal operation, and wherein placing the device under test in the test fixture comprises placing the device under test in the test fixture in an upside-down orientation that is different than the upright orientation. 
     
     
       4. The method defined in  claim 1 , wherein placing the device under test in the test fixture comprises inserting the device under test in a recess in the test fixture to secure the device under test in a desired position. 
     
     
       5. The method defined in  claim 1 , further comprising:
 with antenna test probes arranged along the test waveguide structure, gathering radio-frequency measurements by transmitting the radio-frequency test signals generated by the test unit and receiving corresponding signals that have been passed through at least a portion of the test waveguide structure. 
 
     
     
       6. The method defined in  claim 5 , further comprising:
 obtaining scattering parameter measurements by analyzing the transmitted radio-frequency test signals and the corresponding received radio-frequency test signals. 
 
     
     
       7. The method defined in  claim 6 , further comprising:
 determining whether the device under test contains a manufacturing defect by comparing the scattering parameter measurements to predetermined threshold levels. 
 
     
     
       8. A method of using a test system to test a partially assembled device having a periphery, comprising:
 placing the partially assembled device on a test fixture; and 
 with a plurality of test probes that is formed on the test fixture and that is arranged along the periphery of the partially assembled device when the partially assembled device is placed on the test fixture, transmitting and receiving wireless test signals while the partially assembled device is powered off. 
 
     
     
       9. The method defined in  claim 8 , further comprising:
 obtaining scattering parameter measurements by analyzing the transmitted and received wireless test signals. 
 
     
     
       10. The method defined in  claim 9 , wherein obtaining the scattering parameter measurements comprises obtaining 4-port scattering parameter measurements. 
     
     
       11. The method defined in  claim 9 , further comprising:
 calibrating a reference device to obtain baseline test data. 
 
     
     
       12. The method defined in  claim 11 , further comprising:
 with a test host, determining whether the partially assembled device contains manufacturing defects by comparing the scattering parameter measurements gathered from the partially assembled device to the baseline test data. 
 
     
     
       13. The method defined in  claim 12 , wherein the partially assembled device includes antenna structures that are coupled to radio-frequency transceiver circuitry via transmission line paths, and wherein determining whether the partially assembled device contains manufacturing defects comprises determining whether at least one of the transmission line paths interposed between the antenna structures and the radio-frequency transceiver circuitry in the partially assembled device is broken. 
     
     
       14. The method defined in  claim 11 , wherein the partially assembled device includes antenna resonating structures formed along its periphery, the method further comprising:
 conveying the wireless test signals via a waveguide structure that is formed on the test fixture, wherein the waveguide structure runs along the periphery of the partially assembled device, and wherein the waveguide structure overlaps with at least some of the antenna resonating structures in the partially assembled device. 
 
     
     
       15. Test apparatus, comprising:
 a test unit for generating radio-frequency test signals; 
 a test fixture for receiving a device under test having a periphery; and 
 a plurality of antenna probes arranged on the test fixture, wherein the plurality of antenna probes is positioned along the periphery of the device under test when the device under test is received within the test fixture. 
 
     
     
       16. The test apparatus defined in  claim 15 , wherein the test unit comprises a vector network analyzer. 
     
     
       17. The test apparatus defined in  claim 15 , wherein the plurality of antenna probes comprises four wireless test probes arranged at corners of the periphery of the device under test when the device under test is received within the test fixture. 
     
     
       18. The test apparatus defined in  claim 17 , wherein the four wireless test probes comprises a first pair of antenna test probes having a first size and a second pair of antenna test probes having a second size that is different than the first size. 
     
     
       19. The test apparatus defined in  claim 15 , wherein the device under test includes a number of device antennas formed along its periphery, and wherein the test apparatus includes more antenna probes than the number of device antennas in the device under test. 
     
     
       20. The test apparatus defined in  claim 15 , further comprising:
 a non-conductive region formed on the test fixture, wherein a portion of the non-conductive region serves as a waveguide structure through which the radio-frequency test signals travel around the periphery of the device under test when the device under test is received within the test fixture.

Description:
BACKGROUND 
     This relates to wireless electronic devices and, more particularly, to testing electronic devices with wireless communications circuitry. 
     Electronic devices such as computers, media players, cellular telephones, wireless base stations, and other electronic devices often contain radio-frequency communications circuitry. For example, cellular telephone transceiver circuitry or wireless local area network circuitry may be used to allow a device to wirelessly communicate with external equipment. Antenna structures in the radio-frequency circuitry may be used in transmitting and receiving wireless signals. 
     The antenna performance of an electronic device may depend on how accurately the radio-frequency communications circuitry is manufactured and assembled within the electronic device. Manufacturing defects present in radio-frequency circuits (i.e., defects due to process variation and non-ideal fabrication environments) may have a negative impact on device performance. For example, if defective parts are assembled in a finished device, the finished device may exhibit unsatisfactory wireless performance during production testing. Detection of faults only after assembly is complete results in costly device scrapping or extensive reworking. 
     Mishandling during device assembly operations can also have a detrimental impact on device performance. During device assembly, workers and automated assembly machines may be used to connect connectors for antennas and other components to mating connectors, form welds, machine features into conductive device structures, and otherwise form and interconnect electronic device structures. If care is not taken, however, faults may result that can impact the performance of a final assembled device. For example, a connector may not be seated properly within its mating connector or a metal part may not be machined correctly. In some situations, it can be difficult or impossible to detect and identify these faults, if at all, until assembly is complete and a finished device is available for testing. Detection of faults only after assembly is complete can results in costly device scrapping or extensive reworking. 
     It would therefore be desirable to be able to provide improved ways in which to detect faults during the manufacturing of electronic devices. 
     SUMMARY 
     An electronic device may contain storage and processing circuitry and input-output circuitry such as wireless communications circuitry. The wireless communications circuitry may include a radio-frequency transceiver coupled to antenna structures. The radio-frequency transceiver circuitry may support communications in communications bands such as cellular telephone communications bands and wireless local area network bands. 
     The antenna structures may be formed from an antenna ground and an array of antenna resonating elements that share the antenna ground. The electronic device may have a periphery and there may be, for example, six antenna resonating elements that forms an array of six respective antennas around the periphery of the electronic device. The electric field polarizations of at least some of the antennas may be different. Providing the antenna array with polarization diversity may enhance antenna performance. 
     A radio-frequency test system is provided that can be used for testing an electronic device of the type that includes antenna structures formed along its periphery. The electronic device under test (DUT) may only be partially assembled and may be powered off during testing. The test system may include a test host (e.g., a personal computer), a test unit (e.g., a vector network analyzer) for generating radio-frequency test signals, and a test fixture for receiving the DUT during testing. 
     A non-conductive region may be formed on the test fixture. Antenna test probes may be formed in the non-conductive region. The DUT may be mounted over the non-conductive region during testing. In one arrangement, the DUT may be inserted in a recess in the test fixture in an upside-down orientation that is different than the upright position in which the DUT is oriented during normal operation. While the DUT is mounted on the test fixture, a portion of the non-conductive portion that is arranged along the periphery of the DUT may serve as a test waveguide structure though which radio-frequency test signals can travel around the periphery of the DUT. There may, as an example, be four antenna test probes placed near the corners of the DUT, where a first pair of antenna test probes has a first size and where a second pair of antenna test probes has a second size that is different than the first size. 
     The test unit may be used to transmit and receive corresponding wireless test signals that have propagated through at least a portion of the test waveguide structure. Test data such as scattering parameter measurements may then be obtained based on the transmitted and received test signals. The test host may then be used to determine whether the partially assembled DUT contains any manufacturing defects by comparing the scattering parameter measurements to predetermined (calibrated) baseline data. 
     Further features of the present invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device containing wireless circuitry in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of an illustrative electronic device containing wireless circuitry and associated external equipment that may wirelessly communicate with the electronic device over a wireless communications path in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional top view of an illustrative electronic device of the type shown in  FIG. 1  in accordance with an embodiment of the present invention. 
         FIG. 4  is a cross-sectional side view of an illustrative electronic device of the type shown in  FIG. 1  in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram of an illustrative antenna of the type that may be used in forming an antenna array with multiple antennas in a wireless electronic device in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional side view of a portion of an antenna ground structure and an associated antenna resonating element being used to form an antenna in a wireless electronic device in accordance with an embodiment of the present invention. 
         FIG. 7  is a top view of an antenna array formed from an antenna ground plane and an array of antenna resonating elements surrounding the ground plane in accordance with an embodiment of the present invention. 
         FIG. 8  a diagram of an illustrative test system for testing an electronic device with an antenna array of the type shown in  FIG. 7  in accordance with an embodiment of the present invention. 
         FIG. 9  is a perspective view of an illustrative test fixture having a recess for receiving an electronic device under test in accordance with an embodiment of the present invention. 
         FIG. 10  is a top view showing illustrative test probes that are included in a test system of the type shown in  FIG. 8  in accordance with an embodiment of the present invention. 
         FIGS. 11A and 11B  show graphs in which forward transfer coefficient magnitude and phase data that has been gathered using a test system of the type shown in  FIG. 8  has been plotted as a function of applied signal frequency in accordance with an embodiment of the present invention. 
         FIG. 12  is a flow chart of illustrative steps for operating the test system of  FIG. 8  to test an electronic device of the type shown in  FIGS. 1-7  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Wireless electronic devices such as wireless electronic device  10  of  FIG. 1  may contain wireless circuitry. The wireless circuitry of wireless electronic device  10  may include radio-frequency transceiver circuitry and associated antenna structures for transmitting and receiving wireless signals. Electronic device  10  may be a handheld electronic device such as a portable media player or cellular telephone, may be a portable computer such as a tablet computer or laptop computer, may be a desktop computer, may be a television, may be a wireless access point or other wireless base station, may be a computer monitor, may be a set-top box, may be a gaming console, or may be other electronic equipment. Illustrative configurations in which wireless electronic device  10  is a wireless base station such as a wireless base station that serves as a wireless access point for a wireless local area network and that may be provided with a hard drive or other mass storage device are sometimes described herein as an example. 
     As shown in  FIG. 1 , electronic device  10  may have a housing such as housing  12 . Housing  12  may be formed from one or more housing structures. Housing  12  may include metal structures, plastic structures, glass structures, ceramic structures, and structures formed from other materials. Housing  12  may, if desired, be formed using a unibody construction in which housing  12  or substantially all of housing  12  is formed from a single machined piece of material. Housing  12  may also be formed by joining two or more parts (e.g., first and second housing members, internal housing frame structures, etc.). To allow antennas to operate satisfactorily, the walls of housing  12  may be formed from a dielectric such as plastic or one or more dielectric antenna window structures may be formed in a conductive housing  12 . As an example, the top and four sides of housing  12  may be formed form plastic. 
     Device  10  may include antenna structures and additional electrical components. The antenna structures may be located in an upper portion of housing  12  such as upper portion  16 . The antenna structures may include one or more antennas that are used to wirelessly transmit and receive signals for device  10 . Antenna structures in device  10  may, for example, include multiple antennas organized to form a multiple antenna array. The antenna array may be used for implementing wireless communications schemes such as MIMO (multiple input multiple output) schemes. 
     The additional electrical components may be located in a lower portion of housing  12  such as lower portion  18 . Device  10  may be coupled to a source of alternating current line power or a source of direct current power. For example, device  10  may receive alternating current power through electrical cord  30  and plug  32 . Plug  32  may have prongs  34  that fit into a wall outlet. 
     Device  10  may include data ports, buttons, and other components. Such components may be mounted in a region of device  10  such as region  14  of  FIG. 1 . Buttons may be used for turning on and off device  10 , for making settings adjustments when using device  10 , and for otherwise facilitating user interactions with device  10 . Openings may be formed in the housing wall of device  10  in region  14  of housing  12  or other suitable region to accommodate ports such as audio jacks, digital data ports, etc. Status indicator lights and other input-output devices may also be incorporated in device  10  in a region such as region  14 , if desired. 
       FIG. 2  is a schematic diagram showing illustrative components that may be included in an electronic device such as electronic device  10  of  FIG. 1 . As shown in  FIG. 2 , electronic device  10  may include control circuitry such as storage and processing circuitry  36  and may include associated input-output circuitry  38 . 
     Control circuitry  36  may include storage and processing circuitry that is configured to execute software that controls the operation of device  10 . Control circuitry  36  may include microprocessor circuitry, digital signal processor circuitry, microcontroller circuitry, application-specific integrated circuits, and other processing circuitry. Control circuitry  36  may also include storage such as volatile and non-volatile memory, hard-disk storage, removable storage, solid state drives, random-access memory, memory that is formed as part of other integrated circuits such as memory in a processing circuit, etc. 
     Input-output circuitry  38  may include components for receiving input from external equipment and for supplying output. For example, input-output circuitry  38  may include user interface components for providing a user of device  10  with output and for gathering input from a user. As shown in  FIG. 2 , input-output circuitry  38  may include wireless circuitry  52 . Wireless circuitry  52  may be used for transmitting and/or receiving signals in one or more communications bands such as cellular telephone bands, wireless local area network bands (e.g., the 2.4 GHz and 5 GHz IEEE 802.11 bands), satellite navigation system bands, etc. For example, when device  10  is used as a wireless base station, wireless circuitry  52  may support 2.4 GHz and 5 GHz IEEE 802.11 wireless local area network communications. 
     Wireless circuitry  52  may include transceiver circuitry such as radio-frequency transceiver  40 . Radio-frequency transceiver  40  may include a radio-frequency receiver and/or a radio-frequency transmitter. Radio-frequency transceiver circuitry  40  may be used to handle wireless signals in communications bands such as the 2.4 GHz and 5 GHz WiFi® bands, cellular telephone bands, and other wireless communications frequencies of interest. 
     Radio-frequency transceiver circuitry  40  may be coupled to one or more antennas in antenna structures  44  using transmission line structures such as transmission lines  42 . Transmission lines  42  may include coaxial cables, microstrip transmission lines, transmission lines formed from traces on flexible printed circuits (e.g., printed circuits formed from flexible sheets of polyimide or other layers of flexible polymer), transmission lines formed from traces on rigid printed circuit boards (e.g., fiberglass-filled epoxy substrates such as FR4 boards), or other transmission line structures. If desired, circuitry may be interposed within transmission line structures  42  such as impedance matching circuitry, filter circuitry, switches, and other circuits. This circuitry may be implemented using one or more components such as integrated circuits, discrete components (e.g., capacitors, inductors, and resistors), surface mount technology (SMT) components, or other electrical components. 
     Antenna structures  44  may include inverted-F antennas, patch antennas, loop antennas, monopoles, dipoles, or other suitable antennas. Configurations in which at least one antenna in device  10  is formed from an inverted-F antenna structure are sometimes described herein as an example. Wireless circuitry  52  may use antenna structures  44  to transmit and receive wireless signals such as wireless signals  48 , thereby allowing device  10  to communicate with external equipment  50 . External equipment  50  may be a handheld electronic device such as a portable media player or cellular telephone, may be a portable computer such as a tablet computer or laptop computer, may be a desktop computer, may be a television, may be a wireless access point or other wireless base station, may be a computer monitor, may be a set-top box, may be a gaming console, or may be other electronic equipment. For example, if electronic device  10  has been configured to serve as a wireless base station, external equipment  50  may be one or more tablet computers, cellular telephones, portable computers, desktop computers, media player equipment, and other equipment that communicates with the wireless base station using wireless signals  48 . 
     Input-output circuitry  38  may include buttons and other components  46 . Components  46  may include buttons such as sliding switches, push buttons, menu buttons, buttons based on dome switches, keys on a keypad or keyboard, or other switch-based structures. Components  46  may also include sensors, displays, speakers, microphones, cameras, status indicators lights, etc. 
     A cross-sectional top view of device  10  of  FIG. 1  taken along line  24  and viewed in direction  26  of  FIG. 1  is shown in  FIG. 3 . As shown in  FIG. 3 , housing  12  may have a rectangular outline. Storage such as a hard drive, a solid state drive, or other mass storage device may be mounted within diagonal region  56 . The mass storage device may be used to store large amounts of data (e.g., more than 256 GB, more than 1 TB, etc.). Region  58  may contain power supply circuitry, a fan, control circuitry  36  and input-output circuitry  38  of  FIG. 2 , and other electrical components. Region  54  may contain a heat sink. For example, metal heat sink fins that are used in cooling the hard drive or other storage of region  56  and/or the circuitry of region  58  may be installed in region  54 . 
     Device  10  may also contain printed circuit board  59 . Components such as integrated circuits, connectors, switches, application specific integrated circuits, processors, control circuitry (e.g., storage and processing circuitry  36 ), input-output components such as circuitry  46 , communications circuits (e.g., wired communications circuits and wireless communications circuitry  52 ), and other circuitry for supporting the operation of device  10  may, for example, be mounted no board  59 . As illustrated in  FIG. 3 , board  59  (sometimes referred to as a main logic board) may be mounted between region  56  and region  58 . Arranged in this way, heat sink structures in region  58  may be attached to one or more components on board  59  to cool those components. 
     A cross-sectional side view of device  10  of  FIG. 1  taken along line  20  of  FIG. 1  and viewed in direction  22  is shown in  FIG. 4 . As shown in  FIG. 4 , the components of device  10  may be mounted within the interior of device housing  12 . Hard disk drive  60  or other storage components may, if desired, be mounted within bracket  62  in region  56 . Antenna structures  44  may include antenna ground structure  64  and antenna resonating elements  66 . Bracket  62  may be a metal bracket. Antenna ground structures  64  may be formed from a stamped sheet metal part that is mounted to metal bracket  62 . Antenna ground structures  64  may be grounded to a source of ground potential by virtue of being electrically shorted to metal bracket  62 , which may be grounded. 
     Antennas in an antenna array for device  10  may be formed by mounting antenna resonating elements  66  within the vicinity of antenna ground structures  64 . Antenna ground structures  64  may sometimes be referred to as an antenna can or grounding can or may be referred to as a shared antenna ground in scenarios such as those in which structures  64  form a common ground for each of antenna resonating elements  66 . Portions of antenna resonating elements  66  may be shorted to antenna ground structures  64  using solder or other electrical paths. 
     Antenna resonating elements  66  may be based on patch antenna resonating elements, loop antenna resonating elements, monopole antenna resonating elements, dipole antenna resonating elements, planar inverted-F antenna resonating elements, slot antenna resonating elements, other antenna resonating elements, or combinations of these antenna resonating elements. As an example, antenna resonating elements  66  may be inverted-F antenna resonating elements that are used in forming an array of inverted-F antennas for device  10 . 
       FIG. 5  is a diagram of an illustrative inverted-F antenna  70  formed from inverted-F antenna resonating element  66  and antenna ground  64 . Antenna ground  64  may be a stamped metal ground structure such as antenna ground  64  of  FIG. 4 . Antenna resonating element  66  may be a single arm or multi-arm inverted-F antenna resonating element that is mounted adjacent to antenna ground structures  64  as shown in  FIG. 4 . 
     As shown in  FIG. 5 , antenna resonating element  66  may have a main resonating element arm such as arm  72 . Short circuit branch  74  may be coupled between arm  72  and ground  64 . Antenna feed branch  76  may be coupled between arm  72  and ground  64  in parallel with short circuit branch  74 . Antenna feed branch  76  may form an antenna feed that includes a positive antenna feed terminal (+) and a ground antenna feed terminal (−). A positive transmission line conductor in transmission line structures  42  may be coupled between a positive terminal in radio-frequency transceiver circuitry  40  and positive antenna feed terminal (+). A ground transmission line conductor in transmission line structures  42  may be coupled between a ground terminal in radio-frequency transceiver circuitry  40  and ground antenna feed terminal (−). 
     Resonating element arm  72  may have a single branch or may have a longer branch that is associated with a low band resonance and a shorter branch that is associated with a high band resonance (as an example). Configurations in which inverted-F antenna has three or more different resonating element branches may also be used. The single-arm configuration of antenna resonating element  66  of  FIG. 5  is merely illustrative. 
     Antenna ground structures  64  may be formed from a stamped sheet metal part that is oriented horizontally, as shown in  FIG. 4 . To help avoid undesired reflection-induced resonances in wireless performance and thereby improve antenna performance, it may be desirable to form at least some of the surfaces of antenna ground structures  64  with angles (i.e., with slanted surfaces that form diagonal steps between different ground plane regions). As shown in  FIG. 6 , for example, the sheet metal that is used in forming antenna ground structures  64  may be stamped to form planar horizontal portions such as horizontal portions  78  and  82  and angled portions such as angled portion  80 . Angled surfaces  80  may help reduce the possibility of creating undesired standing wave reflections in the antennas of device  10  and may help evenly distribute the signals from the antennas of device  10 , improving antenna performance while satisfying regulatory requirements for emitted signal levels. 
     As shown in  FIG. 6 , the surfaces of angled (slanted step) portion  80  may be oriented at a 45° angle with respect to horizontal surfaces such as surfaces  78  and  82 . Angled surfaces in antenna ground structures  64  may be oriented at other angles (e.g., angles of more than 45° or less than 45°) with respect to horizontal surfaces such as surfaces  78  and  82 , if desired. The configuration of  FIG. 6  is merely illustrative. 
     A top view of antenna structures  44  is shown in  FIG. 7 . As shown in  FIG. 7 , antenna structures  44  may include antenna ground structures  64  with an approximately rectangular footprint (e.g., a structure with a peripheral edge that outlines an approximately rectangular shape). Multiple antenna resonating elements  66  may be arranged around the periphery of antenna ground structures  64 . There may be, for example, an array of six antennas  70  in antenna structures  44 . In this type of configuration, three of the antennas may be configured to transmit and receive wireless signals in at least a 2.4 GHz wireless local area network communications band and another three of the antennas may be configured to transmit and receive wireless signals in at least a 5 GHz wireless local area network communications band. 
     In each antenna  70 , short circuit branch  74  may be used to couple main resonating element arm  72  to antenna ground  64 . Each antenna has an associated antenna feed formed from positive (+) and ground (−) antenna feed terminals. The positive and ground antenna feed terminals of each antenna feed may be coupled to transmission line structures  42  such as coaxial cables. For example, the antenna feed terminals of each antenna  70  of  FIG. 7  may be coupled to a printed circuit board on which components for radio-frequency transceiver circuitry  40  have been mounted using a respective coaxial cable. 
     Because the inverted-F antenna resonating elements  66  are oriented in different directions in the configuration of  FIG. 7 , antennas  70  exhibit different polarizations, as indicated by the electric fields E associated with each antenna  70  in  FIG. 7 . Placement of antennas  70  within antenna structures  44  so that antennas  70  exhibit different polarizations helps improve wireless signal uniformity and reduces electromagnetic coupling between antennas  70 , thereby improving performance of the antenna array (e.g., when handling MIMO signals). Electromagnetic coupling can also be reduced by ensuring that adjacent antennas such as antennas A 1  and A 2  operate in different bands. 
     The center of antenna structures  44  may be formed from a metal sheet with an approximately rectangular outline (i.e., antenna ground  64 ). Dielectric support structure  84  may surround the periphery of antenna ground  64 . For example, dielectric support structures  84  may have the shape of a strip of dielectric material that runs along the edges of antenna ground  64 , so that the strip of dielectric material forms a ring-shaped dielectric member. Adhesive, fasteners, solder, overmolding, engagement features, or other attachment mechanisms may be used in attaching dielectric support structures  84  to antenna ground structures  64 . Because dielectric support structures  84  may be used in supporting antenna resonating elements  66  for antennas  70 , dielectric support structures  84  are sometimes referred to as dielectric carriers, a dielectric support member, an antenna support structure, an antenna support, or an antenna resonating element support member (as examples). 
     Antenna resonating elements  66  may be formed using conductive structures such as patterned metal foil or metal traces on a dielectric substrate. Metal traces may be patterned using selective laser surface activation followed by electroplating (sometimes referred to as laser direct structuring), by blanket metal deposition using physical vapor deposition equipment or electrochemical deposition followed by photolithographic patterning, by screen printing, etc. The conductive structures of antenna structures  66  may be supported by glass ceramic carriers, plastic carriers, printed circuits, or other dielectric support structures such as dielectric support structures  84 . Conductive materials for antenna resonating elements  66  may, for example, be supported on dielectric supports  84  such as injection-molded plastic carriers, glass or ceramic members, or other insulators. 
     In a configuration in which antenna resonating elements are formed from metal traces on dielectric support structure  84  and in which antenna ground  64  is formed from a stamped sheet metal structure, solder may be used in forming electrical connections  86  between antenna resonating elements  66  and antenna ground. 
     The arrangement of antenna structures  44  as shown in  FIG. 7  is merely illustrative and does not serve to limit the scope of the present invention. If desired, device  10  may include less than six or more than six antennas formed along the periphery of device  10  for supporting communications in any suitable number of radio-frequency bands. The antennas need not be formed in upper portion  16  of device  10 . It should be appreciated that antenna structures  44  may be formed near a lower base portion of device  10  or somewhere in device  10  between upper portion  16  and the lower base portion. 
     As described above, electronic devices such as device  10  may include structures such as antennas, printed circuit boards, connectors, heat sinks, fans, power supply circuitry, and other components that are mounted within the housing of electronic device  10 . Structures such as these may be assembled using automated manufacturing tools. Examples of automated manufacturing tools include automated milling machines, robotic pick-and-place tools for populating printed circuit boards with connectors and integrated circuits, computer-controlled tools for attaching connectors to each other, and automated welding machines (as examples). Manual assembly techniques may also be used in assembling electronic devices. For example, assembly personnel may attach a pair of mating connectors to each other by pressing the connectors together. 
     Regardless of whether operations such as these are performed using automated tools or manually, there will generally be a potential for error. Parts may not be manufactured properly and faults may arise during assembly operations. 
     With conventional testing arrangements, these faults may sometimes be detected after final assembly operations are complete. For example, over-the-air wireless tests on a fully assembled device  10  may reveal that one of the antennas in device  10  is not performing within desired limits. This type of fault may be due to improper connection of a pair of connectors in the signal path between the defective antenna and radio-frequency transceiver  40 . Detection of faults at late stages in the assembly process may, however, result in the need for extensive reworking. It may often be impractical to determine the nature of the fault, forcing the device to be scrapped. 
     Earlier and potentially more revealing and accurate tests may be performed by using wireless probe structures to test partially assembled electronic device structures via electromagnetic coupling mechanisms. An illustrative test system such as test system  100  with wireless (or electromagnetic coupling) probes for use in testing electronic device structures  10  is shown in  FIG. 8 . Device  10  that is fully assembled or partially assembled and that is tested by test system  100  may sometimes be referred to as device structures under test or as a device under test (DUT). 
     As an example, test system  100  may be used to test a partially assembled production DUT  10  after bracket  62  has been assembled within housing  12  (e.g., antenna ground structures  64  may be attached to metal bracket  62 ) and after transmission line paths  42  have been connected between antenna structures  44  and radio-frequency transceiver circuitry  40  mounted on board  59 . In some arrangements, transmission line paths  42  include coaxial cables having radio-frequency (RF) connectors that are mated with corresponding terminals on board  59  and with terminals that are connected to the different antenna feed terminals associated with antenna structures  44 . 
     During assembly of metal bracket  62  to ground structures  64 , it is possible that antenna structures  44  be mechanically damaged or that the connections to antenna structures  44  be electrically broken (e.g., the radio-frequency antenna connectors may be inadvertently unplugged during assembly). Test system  100  may therefore be used to perform electromagnetic coupling based testing on partially assembled DUT  10  to detect such types of manufacturing and assembly defects at an early production stage. Testing DUT  10  using electromagnetic coupling (wireless) techniques in this way can help reduce the risk of cosmetic damages to the production DUT during testing. DUT  10  need not be powered on during testing. Testing in which the device structures under test can be deactivated is sometimes referred to as “passive” testing, passive antenna testing, or passive wireless testing. 
     Referring back to  FIG. 8 , test system  100  may include a test host such as test host  102 , a test unit such as test unit  104 , a test fixture such as test fixture  110 , control circuitry, network circuitry, cabling, and other test equipment. DUT  10  may be mounted on test fixture  110  during testing. Test fixture  110  may be formed from plastic support structures, a rigid printed circuit board substrate such as a fiberglass-filled epoxy substrate (e.g., FR4), a flexible printed circuit (“flex circuit”) formed from a sheet of polyimide or other flexible polymer, or other dielectric material to avoid interference with radio-frequency test measurements. 
     Radio-frequency test unit (sometimes referred to as an RF tester)  104  may be a vector network analyzer (as an example). In the example of  FIG. 8 , test unit  104  may have four RF ports P 1 , P 2 , P 3 , and P 4  through which radio-frequency test signals may be transmitted and received during testing. Ports P 1 , P 2 , P 3 , and P 4  may be respectively coupled to test probes  112 - 1 ,  112 - 2 ,  112 - 3 , and  112 - 4  via different cables  114 . Cables  114  may be coaxial cables (as an example). Test probes  112  (i.e., test probes  112 - 1 ,  112 - 2 ,  112 - 3 , and  112 - 4 ) may serve as test antennas that can be used to emit and receive radio-frequency test signals. In general, antenna probes  112  referred to herein as test antennas or probe antennas, may be implemented using any suitable antenna type (e.g., loop antennas, patch antennas, dipole antennas, monopole antennas, inverted-F antennas, planar inverted-F antennas, coil antennas, open-ended waveguides, horn antennas, etc.). 
     During testing, antenna probes  112  may be placed in the vicinity of DUT  10 . For example, antenna probes  112  may be placed within 10 cm or less of DUT  10 , within 2 cm or less of DUT  10 , or within 1 cm or less of DUT  10  (as examples). These distances may be sufficiently small to place antenna probes  112  within the “near field” of device structures under test  104  (i.e., a location at which signals are received by an antenna that is located within about one or two wavelengths from device structures under test  10  or less). 
     Test probes  112  may be formed as an integral part of test fixture  110  and may be arranged on fixture  110  such that test probes  112  are positioned along the periphery of DUT  10  during testing. A test wave guide structure or region  120  may be formed on test fixture  110  such that when DUT is mounted on test fixture  110 , test signals that are wirelessly transmitted from test probes  112  travel through wave guide structure  120  along the periphery of DUT  10 , as indicated by dotted signal path  122 . Configured in this way, the radio-frequency test signals propagating through wave guide structure  120  are affected by the presence of antenna structures  44  within DUT  10 . 
     Radio-frequency tester  104  may receive commands from test host  102  via path  106  that direct tester  104  to gather desired radio-frequency measurements. If desired, test data can be provided from tester  104  to test host  102  via path  106 . 
     For example, tester  104  may direct radio-frequency tester  104  to produce radio-frequency test signals that are applied to DUT  10  via antenna test probes  112 . Radio-frequency transceiver circuitry  40  in DUT  10  need not be active during testing of DUT  10 . Even without receiving active radio-frequency signals from transceiver  40 , antenna structures  44  in DUT  10  may emit radio-frequency signals when being energized by the test signals generated by tester  104 . Antenna probes  112  may be used to transmit radio-frequency signals to DUT  10  and may be used to receive corresponding radio-frequency signals that have been affected by the presence of antenna structures  44  in DUT  10 . 
     The transmitted and received signals may be processed to compute scattering parameter test data (S-parameter measurements) including complex impedance or reflection coefficient data, complex forward transfer coefficient data, or other suitable data for determining whether DUT  10  contains some defect. 
     In the example of  FIG. 8  in which there are four RF ports, up to 16 different possible 4-port scattering parameter measurements (e.g., S 11 , S 12 , S 13 , S 14 , S 21 , S 22 , . . . , S 43 , and S 44 ) can be gathered if each of the four antenna probes  112  is used to transmit and receive wireless test signals. This is merely illustrative. If desired, only a subset of all the different possible measurements can be taken to reduce test time. For example in some scenarios, only some of the S-parameter measurements are actually “sensitive” to the presence of manufacturing defects (e.g., only the more sensitive measurements need to be taken). In other arrangements, test system  100  may include, more than two, more than three, or more than four wireless test probes positioned in the vicinity of the periphery of DUT  10  during testing. 
       FIG. 9  shows a perspective view of test fixture  110 . Test fixture  110  may include a recess such as recess  150  for receiving DUT  10  during testing. The insertion of DUT  10  within recess  150  ensures that DUT  10  is positioned at a desired predetermined location relative to antenna probes  112  during testing. The antenna test probes may be formed within recess  150  (as an example). Text fixture  110  may serve as a dielectric standoff that separates DUT  10  away from other potentially interfering objects during testing. 
     As shown in  FIG. 9 , DUT  10  may be inserted into test fixture  110  with the upper antenna portion  16  facing downwards toward test fixture  110  (e.g., DUT  10  may be positioned in an upside-down orientation during testing). Arranged in this way, antenna structures  44  are placed closer to the antenna test probes formed within recess  150  than if DUT  10  had been mounted in an upright orientation on test fixture  110 . In the example of  FIG. 9 , components on main logic board  59  are connected to antenna structures  44  via cable paths  42 . In this particular example, one of the cable paths  42  is inadvertently disconnected/unplugged. Test system  100  can be used to detect such types of errors. This is merely illustrative. In general, test system  100  may be used to detect any type of faults associated with antenna structures  44  in DUT  10 . 
     To determine necessary testing criteria, test system  100  may first be used to gather baseline test data from reference devices with no manufacturing/assembly defects. Thereafter when testing a particular production DUT  10 , test data gathered from that DUT  10  can then be compared to the baseline reference data. If the difference between the currently gathered test data and the baseline reference data is less than a predetermined threshold, the DUT may be indicated as a “passing” DUT. If the difference between the currently gathered test data and the baseline reference data is greater than the predetermined threshold, the DUT may be marked as a “failing” DUT (e.g., a DUT with at least some manufacture/assembly defect). 
       FIG. 10  is a top view of test fixture  110  illustrating the formation of test probes  112 . In the diagram of  FIG. 10 , areas on test fixture  110  other than shaded non-conducting region  200  may be covered with conductive material (e.g., a layer of copper, aluminum, silver, gold, nickel, a mixture of these metals, or other suitable conducting material). The four conductive “islands” in dielectric region  200  may serve as the antenna probes  112 . In the example of  FIG. 10 , antenna probes  112 - 1  and  112 - 3  may be physically larger than antenna probes  112 - 2  and  112 - 4 . When DUT  10  is mounted over region  200 , antenna probe  112 - 1  may be placed in the vicinity of the two device antennas  70  in the top left portion as viewed from the top of device  10  (see,  FIG. 7 ), whereas antenna probe  112 - 3  may be placed in the vicinity of the two device antennas  70  in the lower right portion as viewed from the top of device  10 . On the other hand, antenna probe  112 - 2  may be placed in the vicinity of the device antenna  70  in the top right portion of device  10 , whereas antenna probe  112 - 4  may be placed in the vicinity of the device antenna  70  in the lower left portion of device  10 . In other words, test probes  112 - 1  and  112 - 3  are bigger because they are each placed next to two of the device antennas, whereas test probes  112 - 2  and  112 - 4  are relatively smaller because they are each placed next to only one of the device antennas during testing. This is merely illustrative. If desired, test probes  112  may be formed to exhibit any suitable size and shape. 
     When DUT  10  is inserted within recess  150  of test fixture  110 , DUT  10  may cover a portion of region  200 . The region such as region  202  formed between the periphery of DUT  10  and the edge of non-conducting region  200  may serve as a test waveguide structure  202  through which test signals can be conveyed during testing. Radio-frequency test signals generated by tester  104  may propagate along the periphery of DUT  10  via waveguide region  202 , as indicated by arrows  204 . In general, waveguide region  202  should run along the periphery of DUT  10  and should overlap with at least some of the six antennas in DUT  10  while DUT  10  is placed in the test fixture. Propagating test signals along the periphery of DUT  10  in this way may be suitable for testing devices having multiple antennas formed along its periphery (such as the antenna array of  FIG. 7 ). 
     Illustrative test data gathered using test system  100  is shown in  FIGS. 11A and 11B . In  FIG. 11A , the magnitude of forward transfer coefficient S 21  has been plotted as a function of test signal frequency for a frequency range of 0 to 5 GHz. In  FIG. 11B , the phase of forward transfer coefficient S 21  has been plotted as a function of test signal frequency for a frequency range of 0 to 5 GHz. There are two sets of curves in the graphs of  FIGS. 11A and 11B . Curves  300  correspond to baseline data measured from reference devices without any manufacturing defects, whereas curves  302  correspond to test data measured from DUTs  10  with manufacturing defects. As indicated by illustrative frequency ranges  304  and  306  (e.g., about 3.5 to 5 GHz) in  FIGS. 11A and 11B , respectively, curves  302  exhibit more variation than curves  300 . The presence of manufacturing defects may therefore be detected by monitoring the amount that measurements from a particular DUT deviate from the baseline reference data. Other frequency ranges may be investigated if desired (e.g. a range of frequencies covering 1 to 5 GHz, a range of frequencies including frequencies between 2 and 4 GHz, etc.). 
     Illustrative steps involved in operating test system  100  to test DUT  10  are shown in  FIG. 12 . 
     At step  400 , calibration operations may be performed on properly manufactured and assembled devices  10 . In particular, antenna probes  112  may be used to transmit and receive radio-frequency signals in a desired frequency range (e.g., from 0 Hz to 3 GHz, from 3-14 GHz, a subset of one of these frequency ranges, or another suitable frequency range). Signals corresponding to the transmitted signals may be received from the device structures under test and processed with the transmitted signals to obtain scattering parameter measurements or other suitable test data. The scattering parameter measurements or other test measurements that are made on the properly manufactured and assembled device structures may be stored in storage on tester  104  or test host  102  (e.g., in storage on a vector network analyzer, in storage on computing equipment such as a computer or network of computers that are associated with the vector network analyzer, etc.). If desired, the device structures that are tested during the calibration operations of step  400  may be “limit samples” (i.e., structures that have parameters on the edge or limit of the characteristic being tested. Device structures of this type are marginally acceptable and can therefore be used in establishing limits on acceptable device performance during calibration operations. 
     At step  402 , a given production DUT  10  that potentially includes a manufacturing/assembly defect is placed within test fixture  110  of test system  100  (e.g., DUT  10  may be inserted upside-down within recess  150  of test fixture  110 ). Inserted in this way, antenna structures  44  may be brought into the vicinity of the various antenna test probes  112  in test system  100 . 
     At step  404 , test data may be gathered by using antenna probes  112  to receive corresponding RF test signals. For example, antenna probes  112  may be used to transmit and receive radio-frequency test signals in a desired frequency range (e.g., from 0 Hz to 3 GHz, 3 GHz to 14 GHz, or other suitable frequency range, preferably matching the frequency range used in obtaining the calibration measurements of step  400 ). Wireless test data such as scattering parameter measurements or other suitable test data may be gathered. The scattering parameter measurements (phase and magnitude measurements for impedance and forward transfer coefficient) may be stored in storage in tester  104  or test host  102 . 
     At step  406 , the radio-frequency test data may be analyzed. For example, the test data that was gathered during the operations of step  404  may be compared to the baseline (calibration) data obtained during the operations of step  400  (e.g., by calculating the difference between these sets of data and determining whether the calculated difference exceeds predetermined threshold amounts, by comparing test data to the calibration data from limit samples that represents limits on acceptable device structure performance, or by otherwise determining whether the test data deviates by more than a desired amount from acceptable data values). 
     After computing the difference between the test data and the calibration data at one or more frequencies to determine whether the difference exceeds predetermined threshold values, appropriate actions may be taken. For example, if the test data and the calibration data differ by more than a predetermined amount, test host  102  may conclude that DUT  10  contains a fault and appropriate actions may be taken at step  410  (e.g., by issuing an alert, by informing an operator that additional testing is required, by displaying information instructing an operator to rework or scrap the device structures, etc.). If desired, visible messages may be displayed for an operator of system  100  at step  410  using some sort of display. In response to a determination that the test data and the calibration data differ by less than the predetermined amount, test host  102  may conclude that DUT  10  has been manufactured and assembled properly and appropriate actions may be taken at step  408  (e.g., by issuing an alert that the partially assembled DUT  10  has passed testing, by completing the assembly of the structures to form a finished electronic device, by shipping the final assembled electronic device to a customer, etc.). If desired, visible messages may be displayed for an operator of system  100  at step  480 . 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20130612
Publication Date: 20151006
Grant Date: 20151006
Priority Date: 20130612
Inventors: GUTERMAN JERZY
NICKEL JOSHUA G.
SHIU BOON W.
PASCOLINI MATTIA
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W24/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W24/06", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W24/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W24/06", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 52019630