PATENT DOCUMENT

Publication Number: US-9094056-B2
Application Number: US-201314043636-A
Country: US
Kind Code: B2

Title: Test systems with multiple NFC antennas

Abstract:
A test station may include a test host, testing devices, and a test enclosure. A device under test (DUT) having a near-field communications (NFC) antenna may be placed in the test enclosure during production testing. The testing devices may have test antennas that may convey NFC test signals to the DUT in the test enclosure. Distances between test antennas and the DUT may be monitored by measuring path loss from the test antennas throughout testing. The testing station may also include a test unit and an RF test antenna. The test unit may use the RF test antenna to convey RF test signals to the DUT in the test enclosure. The DUT is marked as a passing DUT if gathered test data is satisfactory for each testing device in the test station and distance measurements between the test antennas and the DUT throughout testing are consistent with calibration measurements.

Claims:
What is claimed is: 
     
       1. A method of using a test system that includes first and second near field communications testing devices to test a device under test, comprising:
 communicating with the device under test with the first near field communications testing device; while the first near field communications testing device is communicating with the device under test, communicating with the device under test with the second near field communications testing device; and 
 determining whether a near field communications device antenna in the device under test satisfies design criteria based on test data gathered using the first and second near field communications testing devices. 
 
     
     
       2. The method defined in  claim 1 , further comprising:
 placing the device under test in a shielded test enclosure. 
 
     
     
       3. The method defined in  claim 1 , further comprising:
 positioning the device under test between the first and second near field communications testing devices during testing. 
 
     
     
       4. The method defined in  claim 1 , wherein communicating with the device under test with the first near field communications testing device comprises sending first test signals to the near field communications device antenna with the first near field communications testing device, and wherein communicating with the device under test with the second near field communications testing device comprises sending second test signals to the near field communications device antenna with the second near field communications testing device. 
     
     
       5. The method defined in  claim 1 , wherein determining whether the near field communications device antenna in the device under test satisfies the design criteria comprises determining whether communications between the near field communications device antenna and the first near field communications testing device is satisfactory and determining whether communications between the near field communications device antenna and the second near field communications testing device is satisfactory. 
     
     
       6. The method defined in  claim 5 , further comprising:
 in response to determining that the communications between the near field communications device antenna and the first near field communications test device is satisfactory and that the communications between the near field communications device antenna and the second near field communications test device is satisfactory, determining that the near field communications device antenna in the device under test satisfies design criteria. 
 
     
     
       7. The method defined in  claim 5 , further comprising:
 in response to determining that the communications between the near field communications device antenna and the first near field communications test device is unsatisfactory, determining that the near field communications device antenna in the device under test fails to satisfy design criteria. 
 
     
     
       8. The method defined in  claim 1 , further comprising:
 calibrating the test system to ensure that a distance separating the first and second near field communications testing devices is within a desired range. 
 
     
     
       9. The method defined in  claim 8 , further comprising:
 detecting deviations from the calibrated distance separating the first and second near field communications testing devices by monitoring path loss measurements between the first and second near field communications testing devices; and 
 in response to detecting deviations from the calibrated distance, determining that the test data gathered using the first and second near field communications testing devices is unreliable. 
 
     
     
       10. A test apparatus for testing an electronic device, comprising:
 a first near field communications testing device that communicates with the electronic device; 
 a second near field communications testing device that communicates with the device under test while the first near field communications testing device is communicating with the electronic device; and 
 a test host that determines whether a near field communications device antenna in the electronic device meets desired performance standards based on test data gathered using the first and second near field communications testing devices. 
 
     
     
       11. The test apparatus defined in  claim 10 , wherein the first and second near field communications testing devices comprise near field communications testing antennas that receive near field communication signals from the electronic device. 
     
     
       12. The test apparatus defined in  claim 10 , wherein the first and second near field communications testing devices sends near field communication test signals to the near field communication device antenna in the electronic device. 
     
     
       13. The test apparatus defined in  claim 10 , further comprising:
 a shielded test box in which the electronic device is placed. 
 
     
     
       14. The test apparatus defined in  claim 13 , wherein the shielded test box is a transverse-electromagnetic cell that provides isolation from outside environment for the electronic device when the electronic device is subjected to electromagnetic compatibility radiated tests. 
     
     
       15. The test apparatus defined in  claim 14 , further comprising:
 a radio-frequency test unit; and 
 a radio-frequency test antenna positioned within the shielded text box, wherein the radio-frequency test unit conveys radio-frequency test signals to the electronic device via the radio-frequency test antenna.

Description:
BACKGROUND 
     This relates generally to testing electronic devices and more particularly, to testing electronic devices with wireless communications circuitry. 
     Wireless electronic devices may use long-range wireless communications circuitry such as cellular telephone circuitry to communicate using cellular telephone bands. Electronic devices may use short-range wireless communications circuitry such as wireless local area network communications circuitry to handle communications with nearby equipment. Electronic devices may also be provided with satellite navigation system receivers and other wireless circuitry such as near field communications (NFC) circuitry. Near field communications schemes involve electromagnetically coupled communications over short distances, typically 20 cm or less. 
     Test stations measure the performance levels of each wireless electronic device under test (DUT) to ensure that each DUT satisfies design criteria. A test station typically includes a test host, a tester, and an electromagnetic shielding test enclosure in which the DUT can be placed during testing. An NFC test antenna can be placed within the test enclosure to communicate with NFC circuitry within the DUT. In conventional NFC testing arrangements, a test station would typically include only one NFC test antenna for use in communicating with the wireless DUT. A properly designed DUT (or “passing” DUT) should be able to communicate successfully with the NFC test antenna at a specified distance. 
     Testing a device with only one NFC test antenna allows for the distance between the DUT and the NFC test antenna to be easily adjusted during testing. As a result, it is possible for the test host to obtain inconsistent or inaccurate test data. For example, it is not uncommon for DUTs exhibiting unsatisfactory performance to be improperly categorized as passing DUTs. 
     It may therefore be desirable to provide improved ways for testing NFC communication performance of electronic devices. 
     SUMMARY 
     A test system for testing a device under test (DUT) may include first and second near field communications (NFC) testing devices. The DUT may include an NFC device antenna. The first NFC testing device may communicate with the DUT by sending test signals to the NFC device antenna. While the first NFC testing device is communicating with the device under test, the second NFC testing device may also communicate with the device under test by sending test signals to the NFC device antenna. The test system may determine whether the NFC device antenna in the DUT satisfies design criteria based on test data gathered using the first and second NFC testing devices, such as determining whether communications between the NFC device antenna and the first and second NFC testing devices are satisfactory. 
     The DUT may be placed in a shielded test enclosure (e.g., test box) and positioned between the first and second NFC testing devices during testing. The shielded test box may be a transverse-electromagnetic cell that provides isolation from outside environment for the DUT when the DUT is subjected to electromagnetic compatibility radiated tests. 
     If communications between the NFC device antenna and both the first and second NFC test devices are determined to be satisfactory, the test system may determine that the NFC device antenna in the DUT satisfies design criteria. If the communications between the NFC device antenna in the DUT and the first NFC test device is determined to be unsatisfactory, the test system may determine that the NFC device antenna in the DUT fails to satisfy design criteria. 
     Testing the DUT may include calibrating the test system to ensure that distance separating the first and second NFC testing devices is within a desired range. If deviations from the calibrated distance separating the first and second NFC testing devices are detected, the test system may determine that the test data gathered using the first and second NFC testing devices is unreliable. Deviations from the calibrated distance may be detected by monitoring the path loss between the first and second NFC testing devices. 
     The test system used to perform wireless testing on a wireless electronic device may include a test host. The test system may also include a radio-frequency test unit that conveys radio-frequency test signals to the DUT via a radio-frequency test antenna positioned within the shielded test box. The test system may obtain radio-frequency and NFC test measurements from the wireless electronic device that is undergoing the wireless testing. 
     Testing the wireless electronic device may include retrieving a serial number from a wireless electronic device that is connected to the test host via a wired path, where the serial number identifies that wireless electronic device. A NFC testing device may wirelessly retrieve a near field communications secure identification number from a wireless electronic device that is undergoing wireless testing. The test host may compare the serial number with the NFC secure identification number in order to determine that the wireless electronic device from which the serial number was retrieved is the wireless electronic device from which the NFC secure identification number was retrieved. 
     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 with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram of illustrative wireless circuitry that may be used in an electronic device in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram of a test station that is used to perform NFC testing. 
         FIG. 5  is a diagram of an illustrative test station that can be used to perform NFC testing in accordance with an embodiment of the present invention. 
         FIG. 6  is a graph plotting path loss versus distance in accordance with an embodiment of the present invention. 
         FIG. 7  is a flow chart of illustrative steps for performing NFC testing in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagram of an illustrative test station that can be used to perform NFC testing and RF testing in accordance with an embodiment of the present invention. 
         FIG. 9  is a flow chart of illustrative steps for performing NFC testing and RF testing in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as electronic device  10  of  FIG. 1  may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. The wireless communications circuitry may include antenna structures such as antenna structures that include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. 
     Antenna structures may, if desired, be formed from conductive electronic device structures. The conductive electronic device structures may include conductive housing structures. The housing structures may include a peripheral conductive member that runs around the periphery of an electronic device. The peripheral conductive member may serve as a bezel for a planar structure such as a display and/or may form vertical sidewalls for the device. 
     The antenna structures may be configured to handle both near field communications (e.g., communications in a near field communications band such as a 13.56 MHz band) and non-near-field communications (sometimes referred to as far field communications) such as cellular telephone communications, wireless local area network communications, and satellite navigation system communications. Near field communications typically involve communication distances of less than about 20 cm. Far field communications typically involve communication distances of multiple meters or miles. 
     Signal combining circuitry such as a duplexer or switching circuitry may be used to allow a near field communications transceiver and non-near-field-communications transceiver circuitry to share the antenna structures. By reducing or eliminating the need for separate near field communications antenna structures to handle near field communications signals, antenna structures that are shared between near field communication and non-near-field-communications circuitry can help minimize device size. 
     Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a cellular telephone, or a media player. Device  10  may also be a television, a set-top box, a desktop computer, a computer monitor into which a computer has been integrated, a television, a computer monitor, or other suitable electronic equipment. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material. In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may, for example, be a touch screen that incorporates capacitive touch electrodes. Display  14  may include image pixels formed form light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electronic ink elements, liquid crystal display (LCD) components, or other suitable image pixel structures. A cover glass layer may cover the surface of display  14 . Portions of display  14  such as peripheral regions  20 I may be inactive and may be devoid of image pixel structures. Portions of display  14  such as rectangular central portion  20 A (bounded by dashed line  20 ) may correspond to the active part of display  14 . In active display region  20 A, an array of image pixels may be used to display images for a user. 
     The cover glass layer that covers display  14  may have openings such as a circular opening for button  16  and a speaker port opening such as speaker port opening  18  (e.g., for an ear speaker for a user). Device  10  may also have other openings (e.g., openings in display  14  and/or housing  12  for accommodating volume buttons, ringer buttons, sleep buttons, and other buttons, openings for an audio jack, data port connectors, removable media slots, etc.). 
     Housing  12  may include a peripheral conductive member such as a bezel or band of metal that runs around the rectangular outline of display  14  and device  10  (as an example). The peripheral conductive member may be used in forming the antennas of device  10  if desired. 
     Antennas may be located along the edges of device  10 , on the rear or front of device  10 , as extending elements or attachable structures, or elsewhere in device  10 . With one suitable arrangement, which is sometimes described herein as an example, device  10  may be provided with one or more antennas at lower end  24  of housing  12  and one or more antennas at upper end  22  of housing  12 . Locating antennas at opposing ends of device  10  (i.e., at the narrower end regions of display  14  and device  10  when device  10  has an elongated rectangular shape of the type shown in  FIG. 1 ) may allow these antennas to be formed at an appropriate distance from ground structures that are associated with the conductive portions of display  14  (e.g., the pixel array and driver circuits in active region  20 A of display  14 ). 
     If desired, a first cellular telephone antenna may be located in region  24  and a second cellular telephone antenna may be located in region  22 . Antenna structures for handling satellite navigation signals such as Global Positioning System signals or wireless local area network signals such as IEEE 802.11 (WiFi®) signals or Bluetooth® signals may also be provided in regions  22  and/or  24  (either as separate additional antennas or as parts of the first and second cellular telephone antennas). Antenna structures may also be provided in regions  22  and/or  24  to handle WiMax (IEEE 802.16) signals. 
     In regions  22  and  24 , openings may be formed between conductive housing structures and printed circuit boards and other conductive electrical components that make up device  10 . These openings may be filled with air, plastic, or other dielectrics. Conductive housing structures and other conductive structures may serve as a ground plane for the antennas in device  10 . The openings in regions  22  and  24  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element such as an inverted-F antenna resonating element formed from part of a conductive peripheral housing structure in device  10  front the ground plane, or may otherwise serve as part of antenna structures formed in regions  22  and  24 . 
     Antennas in device  10  may be used to support any communications bands of interest. For example, device  10  may include antenna structures for supporting non-near-field-communications such as local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications. Bluetooth® communications, etc. Device  10  may use at least part of the same antenna structures for supporting near field communications (e.g., communications at 13.56 MHz). 
     A schematic diagram of an illustrative configuration that may be used for electronic device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , electronic device  10  may include control circuitry such as storage and processing circuitry  28 . Storage and processing circuitry  28  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  28  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio codec chips, application specific integrated circuits, etc. 
     Storage and processing circuitry  28  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  28  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  28  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, near field communications protocols, etc. 
     Circuitry  28  may be configured to implement control algorithms that control the use of antennas in device  10 . For example, circuitry  28  may perform signal quality monitoring operations, sensor monitoring operations, and other data gathering operations and may, in response to the gathered data and information on which communications bands are to be used in device  10 , control antenna structures within device  10  being used to receive and process data and/or may adjust one or more switches, tunable elements, or other adjustable circuits in device  10  to adjust antenna performance. As an example, circuitry  28  may control which of two or more antennas is being used to receive incoming signals, may control which of two or more antennas is being used to transmit radio-frequency signals, may control the process of routing incoming data streams over two or more antennas in device  10  in parallel, may tune an antenna to cover a desired communications band, may perform time-division multiplexing operations to share antenna structures between near field and non-near-field communications circuitry, etc. 
     In performing these control operations, circuitry  28  may open and close switches, may turn on and off receivers and transmitters, may adjust impedance matching circuits, may configure switches in front-end-module (FEM) radio-frequency circuits that are interposed between radio-frequency transceiver circuitry and antenna structures (e.g., filtering and switching circuits used for impedance matching and signal routing), may adjust switches, tunable circuits, and other adjustable circuit elements that are formed as part of an antenna or that are coupled to an antenna or a signal path associated with an antenna, and may otherwise control and adjust the components of device  10 . 
     Input-output circuitry  30  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 circuitry  30  may include input-output devices  32 . Input-output devices  32  may include touch screens, buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  32  and may receive status information and other output from device  10  using the output resources of input-output devices  32 . 
     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, 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 satellite navigation system receiver circuitry such as Global Positioning System (GPS) receiver circuitry  35  (e.g., for receiving satellite positioning signals at 1575 MHz) or satellite navigation system receiver circuitry associated with other satellite navigation systems. 
     Wireless local area network transceiver circuitry  36  in wireless communications circuitry  34  may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and may handle the 2.4 GHz Bluetooth® communications band. 
     Circuitry  34  may use cellular telephone transceiver circuitry  38  for handling wireless communications in cellular telephone bands such as bands in frequency ranges of about 700 MHz to about 2700 MHz or bands at higher or lower frequencies. 
     Wireless communications circuitry  34  may include near field communications circuitry  42 . Near field communications circuitry  42  may handle near field communications at frequencies such as the near field communications frequency of 13.56 MHz or other near field communications frequencies of interest. 
     Circuitry  44  such as satellite navigation system receiver circuitry  35 , wireless local area network transceiver circuitry  36 , and cellular telephone transceiver circuitry  38  that does not involve near field communications may sometimes collectively be referred to as non-near-field communications circuitry or far field communications circuitry. 
     Antenna structures  40  may be shared by non-near-field communications circuitry  44  and near field communications circuitry  42 . 
     If desired, communications circuitry  34  may include circuitry for other short-range and long-range wireless links. For example, wireless communications circuitry  34  may include wireless circuitry for receiving radio and television signals, paging circuits, etc. In near field communications, wireless signals are typically conveyed over distances of less than 20 cm. 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 antenna structures  40 . Antenna structures  40  may include one or more antennas. Antennas structures  40  may be formed using any suitable antenna types. For example, antenna structures  40  may include antennas with resonating elements that are formed from loop antenna structure, patch antenna structures, inverted-F antenna structures, closed and open slot antenna structures, planar inverted-F antenna structures, helical antenna structures, strip antennas, monopoles, dipoles, hybrids of these designs, etc. 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. 
     To accommodate near field communications within the potentially tight confines of device housing  12 , antenna structures  40  may be shared between non-near-field communications circuitry  44  and near field communications circuitry  42 . When, for example, it is desired to transmit and receive cellular telephone signals or other non-near-field communications, antenna structures  40  may be used by transceiver circuitry  38 . When it is desired to transmit and receive near field communications signals, antenna structures  40  may be used to near field communications circuitry  42 . 
     Device  10  can be controlled by control circuitry that is configured to store and execute control code for implementing control algorithms (e.g., antenna diversity control algorithms and other wireless control algorithms). As shown in  FIG. 3 , control circuitry  42  may include storage and processing circuitry  28  (e.g., a microprocessor, memory circuits, etc.) and may include baseband processor  58 . Baseband processor  58  may form part of wireless circuitry  34  and may include memory and processing circuits (i.e., baseband processor  58  may be considered to form part of the storage and processing circuitry of device  10 ). 
     Baseband processor  58  may provide data to storage and processing circuitry  28  via path  48 . The data on path  48  may include raw and processed data associated with wireless (antenna) performance metrics for received signals such as received power, transmitted power, frame error rate, bit error rate, channel quality measurements based on received signal strength indicator (RSSI) information, channel quality measurements based on received signal code power (RSCP) information, channel quality measurements based on signal-to-interference ratio (SINR) and signal-to-noise ratio (SNR) information, channel quality measurements based on signal quality data such as Ec/lo or Ec/No data, information on whether responses (acknowledgements) are being received from a cellular telephone tower corresponding to requests from the electronic device, information on whether a network access procedure has succeeded, information on how many re-transmissions are being requested over a cellular link between the electronic device and a cellular tower, information on whether a loss of signaling message has been received, information on whether paging signals have been successfully received, and other information that is reflective of the performance of wireless circuitry  34 . This information may be analyzed by storage and processing circuitry  28  and/or processor  58  and, in response, storage and processing circuitry  28  (or, if desired, baseband processor  58 ) may issue control commands for controlling wireless circuitry  34 . For example, storage and processing circuitry  28  may issue control commands on path  52  and path  50 . 
     Wireless circuitry  34  may include radio-frequency transceiver circuitry such as radio-frequency transceiver circuitry  60  and radio-frequency front-end circuitry  62 . Radio-frequency transceiver circuitry  60  may include one or more radio-frequency transceivers such as transceivers  57  and  63  (e.g., one or more transceivers that are shared among antennas, one transceiver per antenna, etc.). In the illustrative configuration of  FIG. 3 , radio-frequency transceiver circuitry  60  has a first transceiver such as transceiver  57  that is associated with path (port)  54  (and which may be associated with path  44 ) and a second transceiver such as transceiver  63  that is associated with path (port)  56  (and which may be associated with path  46 ). Transceiver  57  may include a transmitter such as transmitter  59  and a receiver such as receiver  61  or may contain only a receiver (e.g., receiver  61 ) or only a transmitter (e.g., transmitter  59 ). Transceiver  63  may include a transmitter such as transmitter  67  and a receiver such as receiver  65  or may contain only a receiver (e.g., receiver  65 ) or only a transmitter (e.g., transmitter  59 ). 
     Baseband processor  58  may receive digital data that is to be transmitted from storage and processing circuitry  28  and may use path  46  and radio-frequency transceiver circuitry  60  to transmit corresponding radio-frequency signals. Radio-frequency front end  62  may be coupled between radio-frequency transceiver  60  and antennas  40  and may be used to convey the radio-frequency signals that are produced by transmitters  59  and  67  to antennas  40 . Radio-frequency front end  62  may include radio-frequency switches, impedance matching circuits, filters, and other circuitry for forming an interface between antennas  40  and radio-frequency transceiver  60 . 
     Incoming radio-frequency signals that are received by antennas  40  may be provided to baseband processor  58  via radio-frequency front end  62 , paths such as paths  54  and  56 , receiver circuitry in radio-frequency transceiver  60  such as receiver  61  at port  54  and receiver  63  at port  56 , and paths such as paths  44  and  46 . Baseband processor  58  may convert these received signals into digital data that is provided to storage and processing circuitry  28 . Baseband processor  58  may also extract information from received signals that is indicative of signal quality for the channel to which the transceiver is currently tuned. For example, baseband processor and/or other circuitry in control circuitry  42  may analyze received signals to produce bit error rate measurements, measurements on the amount of power associated with incoming wireless signals, strength indicator (RSSI) information, received signal code power (RSCP) information, signal-to-interference ratio (SINR) information, signal-to-noise ratio (SNR) information, channel quality measurements based on signal quality data such as Ec/lo or Ec/No data, etc. This information may be used in controlling which antenna(s) to use in device  10 . For example, a control algorithm running on control circuitry  42  may be used to place device  10  into a dual antenna mode in which both antennas are operating or a single antenna mode in which a single antenna is operating based on channel quality measurements such as these and other information. The control algorithm may also use channel quality measurements to select which antenna to use during single antenna mode operations. 
     Radio-frequency front end  62  may include a switch that is used to connect transceiver  57  to antenna  40 B and transceiver  63  to antenna  40 A or vice versa. The switch may be configured by control signals received from control circuitry  42  over path  50 . Circuitry  42  may, for example, adjust the switch to select which antenna is being used to transmit radio-frequency signals (e.g., when it is desired to share a single transmitter in transceiver  60  between two antennas) or which antenna is being used to receive radio-frequency signals (e.g., when it is desired to share a single receiver between two antennas). 
     If desired, antenna selection may be made by selectively activating and deactivating transceivers without using a switch in front end  62 . For example, if it is desired to use antenna  40 B but not antenna  40 A, transceiver  57  (which may be coupled to antenna  40 B through circuitry  62 ) may be activated and transceiver  63  (which may be coupled to antenna  40 A through circuitry  62 ) may be deactivated. If it is desired to use antenna  40 A but not antenna  40 B, circuitry  42  may activate transceiver  63  and deactivate transceiver  57 . Combinations of these approaches may also be used to select which antennas are being used to transmit and/or receive signals. When it is desired to receive incoming signals such as paging signals using both antennas, transceiver  57  and transceiver  63  may be simultaneously activated to place device  10  in a dual antenna mode. 
     Control operations such as operations associated with configuring wireless circuitry  34  to transmit or receive radio-frequency signals through desired antennas  40  may be performed using a control algorithm that is implemented on control circuitry  42  (e.g., using the control circuitry and memory resources of storage and processing circuitry  28  and baseband processor  58 ). 
     During testing, device  10  may be tested in a test system having a test station such as test station  102  of  FIG. 4 . Electronic devices that are being tested in the test system may sometimes be referred to as devices under test (DUTs). DUT  10  may be loaded with a test operating system (e.g., a simplified operating system that lacks a full Internet Protocol (IP) stack implementation) or a normal user operating system (e.g., an operating system that includes a full Internet Protocol (IP) stack implementation). DUT  10  may include wireless performance measurement circuitry capable of analyzing received test signals. DUT  10  may be capable of computing and storing radio-frequency downlink metrics such as bit error rate measurements, signal-to-noise ratio measurements, measurements on the amount of power associated with incoming wireless signals, channel quality measurements based on received signal strength indicator (RSSI) information, channel quality measurements based on received signal code power (RSCP) information, channel quality measurements based on signal-to-interference ratio (SINR) and signal-to-noise ratio (SNR) information, channel quality measurements based on signal quality data such as Ec/lo or Ec/No data, etc. 
     A test system may include multiple test stations such as test station  102 . Each test station  102  includes a test host  104 , a testing device  106 , and a test enclosure  110 . Test host  104  is a personal computer. Testing device  106  generates NFC test signals to DUT  10  and receives NFC test signals from DUT  10 . Testing device  106  receives commands from test host  104 . 
     During testing, DUT  10  is placed within test enclosure  110 . Testing device  106  includes a processor  112  and test antenna  114 . Processor  112  is coupled to test host  104 . Testing device  106  is used for communicating over short distances using near field electromagnetic coupling. Test antenna  114  is used to radiate corresponding near field electromagnetic signals to DUT  10 . Test antenna  114  is used during production testing to perform over-the-air testing on DUT  10  (e.g., so that NFC test signals are conveyed between testing device  106  and DUT  10  via NFC test antenna  114 ). 
     During testing, test signals are conveyed between test antenna  114  and DUT  10  as indicated by arrow  130 . As shown in  FIG. 4 , DUT  10  and test antenna  114  are separated by a distance dP. Distance dP is within a desired range as determined by product requirements (i.e., test signals between DUT  10  and test antenna  114  should be transmitted and received within a specified distance range). Since typically only one test antenna  114  is used for testing the NFC capabilities of DUT  10 , distance dP could be adjusted during testing to be outside of the desired range, resulting in unreliable testing results gathered at test host  104 . For example, a test operator could move DUT  10  closer to test antenna  114  to obtain a “pass” even though DUT  10  may not transmit or receive NFC signals according to performance criteria if distance dP is within the desired range (e.g., a false pass may be improperly obtained by simply moving the DUT closer to NFC test antenna  114 ). It would therefore be desirable to provide a test system that is insusceptible to such types of erroneous test data. 
       FIG. 5  shows one suitable arrangement of a test system having a test station such as test station  202  in which DUT  10  may be tested. During testing, many wireless devices (e.g., tens, hundreds, thousands, or more of devices  10 ) may be tested in the test system. The test system may include test accessories, computers, network equipment, tester control boxes, cabling, test enclosures, and other test equipment for generating and receiving radio-frequency test signals and gathering test results. The test system may include multiple test stations such as test stations  202 . There may, for example, be eighty test stations  202  at a given test site. The test system may include any desired number of test stations to achieve desired test throughput. 
     Each test station  202  may include a test host such as test host  204 , multiple testing devices such as NFC testing devices  206 - 1  and  206 - 2 , and a test enclosure such as test enclosure  210 . Test host  204  may, for example, be a personal computer or other types of computing equipment. Test station  202  having two NFC testing devices is merely illustrative. Test station  202  may include any number of testing devices (e.g., test station  202  may include NFC testing device  206 - 3 ; NFC testing devices  206 - 1  and  206 - 2  may be two of many NFC testing devices). NFC testing devices  206  (e.g., NFC testing devices  206 - 1  and  206 - 2 ) may be placed in any orientation using positioners  207  with respect to DUT  10  in test enclosure  210 . In the example of  FIG. 5 , DUT  10  may be positioned between two parallel NFC testing devices  206  (e.g., DUT  10  may also be oriented parallel to the two testing devices). In certain embodiments, one or more NFC testing devices may be placed in a non-parallel (or “tilted”) orientation with respect to DUT  10  (see, e.g., additional NFC testing device  206 - 3  in  FIG. 5 ). NFC testing devices  206 - 1  and  206 - 2  may generate NFC test signals and may be used to perform NFC measurements on signals received from DUT  10 . 
     During testing, at least one DUT  10  may be placed within test enclosure  210 . Test enclosure  210  may be a shielded enclosure (e.g., a shielded test box) that is used to provide isolation when performing electromagnetic compatibility radiated tests without experiencing interference from outside environment. 
     NFC testing devices  206 - 1  and  206 - 2  may each have a processor  212  and a test antenna  214 . Processor  212  may be coupled to test host  204  via a cable (see, e.g., conductive paths  216 - 1  and  216 - 2  connecting processors  212  to test host  204 ). NFC testing devices  206 - 1  and  206 - 2  may be used for testing communication over short distances using near field electromagnetic coupling. Each DUT  10  may include NFC device antenna  40 -NFC. Test antenna  214  may be used to radiate corresponding near field electromagnetic signals to NFC device antenna  40 -NFC during production test procedures to perform over-the-air testing on DUT  10  (e.g., so that NFC frequency test signals may be conveyed between NFC testing devices  206 - 1  and  206 - 2  and DUT  10  via NFC test antenna  214 ). Test antenna  214  may, as an example, be a microstrip antenna such as a microstrip patch antenna. 
     During testing, NFC testing devices  206 - 1  and  206 - 2 , and antenna  40 -NFC may convey test signals over-the-air to each other as shown by arrows  230 - 1  and  230 - 2 , respectively. Test antenna  214  of NFC testing devices  206 - 1  and  206 - 2  may be separated from antenna  40 -NFC by distances dA and dB respectively. DUT  10  may be marked as a passing DUT by test host  204  if, for example, device antenna  40 -NFC is able to transmit and receive test signals from test antenna  214  of both NFC testing devices  206 - 1  and  206 - 2  while distances dA and dB are within a specified range. 
     Unwanted adjustment of distances dA and dB to be outside of the specified range may occur during testing. As an example, if antenna  40 -NFC does not properly receive test signals from testing device  206 - 1 , distance dA may be reduced by moving either DUT  10  or NFC testing devices  206  using positioners  207  in an attempt to force DUT  10  to pass the NFC testing. For example, a DUT that is unable to successfully communicate to an NFC testing device  206  may be moved closer to the NFC testing device to obtain a falsely “successful” NFC communication testing result. Alternatively, an NFC testing device may be moved closer using positioners  207  to the unsuccessful DUT to obtain similarly unreliable testing measurements. 
     To prevent misleading testing results due to unwanted variations in distances dA and dB, test antennas  214  of NFC testing devices  206 - 1  and  206 - 2  may be calibrated so that distance dC is within a desired range prior to sending NFC test signals to DUT  10 . To ensure that NFC testing devices  206  were not moved closer to DUT  10  after calibration, test host  204  may confirm that distance dC stays within the desired calibrated range throughout testing before allowing a DUT to pass. In other words, a pass for DUT  10  may not be obtained solely based on NFC test data collected via NFC testing devices  206 - 1  and  206 - 2 . DUT  10  may only be allowed to pass if DUT  10  is physically separated from the NFC testing devices  206  by distances dA and dB within a desired range. 
     Testing devices  206 - 1  and  206 - 2  cannot be moved during testing without being detected by test host  204 . Thus, only DUT  10  can be moved to vary distances dA and dB in an attempt to force a poorly performing DUT to pass the NFC testing. Because distance dC is fixed, reducing distance dA necessarily increases distance dB and vice versa. In other words, moving DUT  10  closer to testing device  206 - 1  (i.e., reducing distance dA) in an attempt to achieve successful NFC communication with testing device  206 - 1  would require moving DUT  10  farther away from testing device  206 - 2  (i.e., increasing distance dB). This would result in failed NFC communication between DUT  10  and testing device  206 - 2 . DUT  10  may only be considered a passing DUT if antenna  40 -NFC is able to successfully receive signals from and transmit signals to antenna  214  of both testing devices  206 - 1  and  206 - 2 . 
     Test station  202  may be calibrated prior to testing to ensure that measurements taken across different test stations, different DUTs, and/or different time points are consistent with one another. Sources of offset (error) that may exist from one test station to another include OTA path loss (e.g., path loss associated with the propagation of NFC frequency signals as they propagate through air, path loss associated with the behavior of each test antenna  214  during actual wireless transmission, etc.) and variations in each testing device  206 - 1  and  206 - 2  (e.g., process, voltage, and temperature variations that may affect the operation of each tester). 
     Path loss can be defined as the attenuation in power as wireless signals propagate through a particular medium. The OTA path loss in each test station  202  is typically unique, because it is challenging to manufacture test components (e.g., test antennas  214 ) that are exactly identical to one another and to configure each test station  102  with an identical spatial arrangement. Path loss may be sensitive to the location of the test antenna and to the placement of DUT  10  within test chamber  210 . 
       FIG. 6  shows an illustrative diagram plotting path loss as a function of the distance between testing devices  206 - 1  and  206 - 2 . Distance calibration between testing devices may be performed using at least two testing devices  206 - 1  and  206 - 2 . Test host  204  may direct testing device  206 - 1  to generate NFC test signals to testing device  206 - 2  at a requested output power level. Testing device  206 - 2  may receive the test signals and send corresponding data back to test host  204  data including power level information (e.g., RSSI, RSCP, or other receive signal quality measurements) of the test signals received. To compute downlink path loss, test host  204  may subtract the power level received by testing device  206 - 2  from the requested output power level. Path loss measured in this way may be recomputed multiple times in the same direction (e.g. sending test signals from testing device  206 - 1  to testing device  206 - 2 ) or in different directions (e.g. sending test signals from testing device  206 - 2  to testing device  206 - 1 ). Path loss measurements may be proportional to the distance dC between testing devices  206 - 1  and  206 - 2 , so the distance dC can be accurately predicted from path loss measurements according to the trend line  240  of  FIG. 6 . Test host  204  may recognize deviations from the calibrated distance by monitoring the distance (i.e., through path loss measurements) between NFC testing devices  206 - 1  and  206 - 2  throughout testing. Inconsistencies in the measured path loss and the calibrated path loss would indicate that DUT  10  should be re-tested. 
       FIG. 7  shows illustrative steps involved in testing DUT  10  using test station  202 . At step  250 , prior to testing DUT  10 , test station  202  may be calibrated to ensure that distance dC between NFC testing devices  206 - 1  and  206 - 2  is within a desired range and does not change throughout testing. The test station may be calibrated by measuring path loss between NFC testing devices as described above in connection with  FIG. 6 . 
     At step  252 , once the test station is calibrated, DUT  10  may be inserted between NFC testing devices  206 - 1  and  206 - 2 . At step  254 , NFC testing devices  206 - 1  and  206 - 2  may send NFC test signals to DUT  10  and test host  204  determines whether DUT  10  passes or fails. If the DUT fails at any one of the NFC testing devices, the DUT may be repositioned and retested (step  256 ). At step  258 , test host  204  may once again determine whether DUT  10  satisfies NFC communications criteria with both NFC testing devices  206 - 1  and  206 - 2 . If DUT  10  still does not pass all NFC testing units after retesting and does not meet satisfactory performance NFC reception criteria, DUT  10  may be removed from test station  202  for repair (step  260 ). If DUT  10  passes testing with both NFC testing devices  206 - 1  and  206 - 2 , DUT  10  may be ready for testing at a subsequent test station (step  262 ). 
       FIG. 8  shows another suitable test system such as a test system having a test station such as test station  302  in which DUT  10  may be tested. The test system may include multiple test stations such as test station  302 . Each test station  302  may include a test host such as test host  304 , a test unit  305 , multiple testers such as NFC testing devices  306 - 1  and  306 - 2 , and a test enclosure such as test enclosure  310 . Test host  304  may, for example, be a personal computer or other types of computing equipment. Test station  302  may include a test unit such as test unit  305 . Test unit  305  may be a test unit for radio frequency (RF) communication that includes an RF antenna such as RF test antenna  314 -RF. RF testing may occur in an enclosure such as enclosure  310 . Test enclosure  310  may be a shielded enclosure (e.g., a shielded test box) that provides RF isolation when performing electromagnetic compatibility radiated tests without experiencing interference from outside environment. Test enclosure  310  may be a transverse-electromagnetic cell (TEM) cell that may include an RF antenna such as RF antenna  314 -RF, a DUT such as DUT  10 , and NFC testing devices such as NFC testing devices  306 - 1  and  306 - 2 . 
     Test station  302  having testing devices  306 - 1  and  306 - 2  is merely illustrative. Test station  302  may include any number of testing devices (e.g., test station  302  may include additional NFC testing device  306 - 3 ; NFC testing device  306 - 1  and  306 - 2  may be two of many testing devices). NFC testing devices  306  may be in any orientation relative to DUT  10  in test enclosure  310  including parallel as shown by NFC testing devices  306 - 1  and  306 - 2  and tilted as shown by additional NFC testing device  306 - 3 . NFC testing devices  306 - 1  and  306 - 2  may generate NFC test signals and perform NFC measurements on signals received from DUT  10 . Test enclosure  310  may also be referred to as TEM cell  310 . 
     Each NFC testing device  306  may have a processor  312  and a NFC test antenna  314 -NFC. DUT  10  may have RF antenna  40 -RF and NFC antenna  40 -NFC. During testing, at least one DUT  10  may be placed within TEM cell  310  between NFC testing device  306 - 1  and  306 - 2 . Two types of testing may occur in TEM cell  310 : RF testing via RF test antenna  314 -RF and NFC testing via NFC test antenna  314 -NFC. During RF testing, test unit  305  may transmit a test signal via RF test antenna  314 -RF at a cellular frequency to test RF communication functionality and performance of RF antenna  40 -RF in DUT  10 . During NFC testing, test antenna  314 -NFC may radiate NFC signals to NFC antenna  40 -NFC in DUT  10  to test NFC communication functionality and performance of NFC antenna  40 -NFC in DUT  10 . 
     Test station  302  may be calibrated such that NFC testing devices  306 - 1  and  306 - 2  are separated by a distance within a specified range. During NFC testing, testing devices  306 - 1 ,  306 - 2 , and antenna  40 -NFC may convey test signals over-the-air to each other. Testing devices  306 - 1  and  306 - 2  may convey test data to each other throughout NFC testing that may include power level information. The power level information may be relayed by processor  312  to test host  304 , which can determine whether NFC testing devices  306  are separated by the calibrated distance. If test host  304  detects that the distance between NFC testing devices  306  are not within the desired calibrated range, then test station  302  may be re-calibrated to re-test DUT  10 . 
       FIG. 9  shows illustrative steps for testing DUT  10  using test station  302  of the type described in connection with  FIG. 9 . At step  350 , DUT  10  may be connected via a cable to test host  304 . At step  352 , test host  304  may read a serial number from DUT  10  (e.g., test host  304  may retrieve a serial number from DUT  10  via a wired path connecting test host  304  to DUT  10 ). At step  354 , test host  304  may configure DUT  10  for RF testing and NFC testing (i.e., to obtain RF and NFC test measurements from DUT  10 ). At step  356 , DUT  10  may be disconnected from test host  304 . 
     At step  358 , NFC testing devices  306 - 1  and  306 - 2  may be calibrated such that they are separated by a distance within a desired range. At step  360 , DUT  10  may be placed in TEM cell  310 . At step  362 , desired testing may be performed on DUT  10 , which may include steps  364  and  366 . At step  364 . RF test antenna  314 -RF may test the performance of RF antenna  40 -RF of DUT  10  by sending test signals at frequencies within desired ranges. These ranges may include frequencies corresponding to Global Positioning System (GPS) communications (1575 MHz band). WiFi® (IEEE 802.11) communications (2.4 GHz and 5 GHz bands), Bluetooth® communications (2.4 GHz band), and cellular telephone communications (700 MHz to about 2700 MHz bands). 
     At step  366 , NFC test antenna  314 -NFC may retrieve a secure identification (ID) number specific to DUT  10  that can only be retrieved via NFC frequency communication to NFC test antenna  314 -NFC. NFC test antenna  314 -NFC may also send power data to each other, which can then be relayed via processor  312  to test host  304  to calculate the distance between NFC testing devices  306 - 1  and  306 - 2 . At step  368 , DUT  10  may be removed from TEM cell  310 . 
     At step  370 , DUT  10  may be reconnected to test host  304  via a cable. At step  372 , test host  304  may determine whether DUT  10  meets all desired performance standards being tested in test station  302 . Step  372  may include steps  374 ,  376 , and  378 . At step  374 , test host  304  may compare the NFC secure ID and the serial number to confirm that DUT  10  was not replaced with another DUT between the serial number reading (step  352 ) and the NFC secure ID retrieval (step  366 ) to “cheat” the NFC testing. At step  376 , test host  304  may determine whether DUT  10  passes RF testing based on the RF data (acquired at step  364 ). At step  378 , test host  304  may determine whether DUT  10  passes NFC testing based on NFC data (acquired at step  366 ). 
     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: 20131001
Publication Date: 20150728
Grant Date: 20150728
Priority Date: 20131001
Inventors: OUYANG YUEHUI
PASCOLINI MATTIA
DARNELL DEAN F.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B17/373", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/0043", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/318", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W24/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/21", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B17/21", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B17/318", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B17/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B17/373", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B5/70", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B5/73", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/70", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 52740623