PATENT DOCUMENT

Publication Number: US-9116232-B2
Application Number: US-201213447015-A
Country: US
Kind Code: B2

Title: Methods and apparatus for testing satellite navigation system receiver performance

Abstract:
A test system for performing over the air testing on a device under test (DUT) with satellite navigation system capability is provided. The test system may include a test host, a satellite navigation system emulator, a test chamber in which the DUT may be placed during testing, and test antennas mounted inside the test chamber. The satellite navigation system emulator may receive ephemeris and almanac data and may generate corresponding simulated test signals to be transmitted to the DUT via the test antennas. The test antennas may be mounted on fixed or rotatable ring-shaped antenna mounting structures configured to emulate respective orbital planes in a given satellite constellation that is currently being characterized. The DUT may also be rotated during testing to emulate user movement.

Claims:
What is claimed is: 
     
       1. A radio-frequency test system for testing an electronic device, comprising:
 a first plurality of test antennas configured to emulate satellites associated with a first orbital plane in a given satellite constellation; 
 a second plurality of test antennas configured to emulate satellites associated with a second orbital plane in the given satellite constellation; and 
 a satellite navigation system simulator configured to receive ephemeris and almanac data and to generate radio-frequency test signals to be transmitted to the electronic device using the first plurality of test antennas and the second plurality of test antennas based on the ephemeris and almanac data. 
 
     
     
       2. The radio-frequency test system defined in  claim 1  further comprising:
 an anechoic test chamber in which the first plurality of test antennas and the second plurality of test antennas are mounted, wherein the electronic device is placed within the anechoic test chamber during testing. 
 
     
     
       3. The radio-frequency test system defined in  claim 1  further comprising:
 a first antenna mounting structure on which the first plurality of test antennas is mounted; and 
 a second antenna mounting structure on which the second plurality of test antennas is mounted. 
 
     
     
       4. The radio-frequency test system defined in  claim 3 , wherein the first and second antenna mounting structures comprises ring-shaped antenna mounting structures. 
     
     
       5. The radio-frequency test system defined in  claim 4  further comprising:
 positioning equipment configured to rotate the first and second ring-shaped antenna mounting structures during testing. 
 
     
     
       6. The radio-frequency test system defined in  claim 1  further comprising:
 a positioner for moving the electronic device relative to the first plurality of test antennas and the second plurality of test antennas during testing. 
 
     
     
       7. The radio-frequency test system defined in  claim 1  further comprising:
 a test host configured to supply the ephemeris and almanac data to the satellite navigation system simulator. 
 
     
     
       8. A method for using a test system to test a device under test having a satellite navigation system receiver, wherein the test system includes a radio-frequency tester and a plurality of test antennas, the method comprising:
 with the radio-frequency tester, generating radio-frequency test signals; 
 with the plurality of test antennas, radiating the radio-frequency test signals generated using the radio-frequency tester, wherein each test antenna in the plurality of test antennas is configured to emulate a respective satellite in a given satellite constellation; and 
 while the radio-frequency test signals are transmitted from the plurality of test antennas to the device under test, moving the device under test. 
 
     
     
       9. The method defined in  claim 8 , wherein the test system further includes an anechoic test chamber in which the plurality of test antennas are mounted, the method further comprising:
 placing the device under test within the anechoic test chamber. 
 
     
     
       10. The method defined in  claim 8 , wherein the radio-frequency tester comprises a satellite navigation system simulator, the method further comprising:
 with the satellite navigation system simulator, receiving ephemeris and almanac data, wherein generating the radio-frequency test signals comprises generating the radio-frequency test signals with the satellite navigation system simulator based on the received ephemeris and almanac data. 
 
     
     
       11. The method defined in  claim 8 , wherein the test system further includes at least one ring-shaped antenna mounting structure to which the plurality of test antennas is mounted, the method further comprising:
 with positioning equipment, rotating the at least one ring-shaped antenna mounting structure during testing, wherein the plurality of test antennas mounted on the at least one ring-shaped antenna mounting structure is configured to emulate satellites associated with an orbital plane in a satellite constellation selected from the group consisting of: a Global Positioning System (GPS) constellation and a Global Navigation Satellite System (GLONASS) constellation. 
 
     
     
       12. The method defined in  claim 8 , wherein the test system further includes a test host, the method further comprising:
 with the test host, retrieving signal strength measurements from the device under test, wherein the signal strength measurements are computed by the device under test based on the radio-frequency test signals received using the satellite navigation system receiver. 
 
     
     
       13. The method defined in  claim 12  further comprising:
 with the test host, computing an average signal strength value based on at least a portion of the signal strength measurements. 
 
     
     
       14. The method defined in  claim 13  further comprising:
 determining whether the satellite navigation system receiver satisfies design criteria by comparing the average signal strength value to a predetermined threshold value.

Description:
BACKGROUND 
     This invention relates to electronic devices and more particularly, to portable electronic devices with satellite navigation system capabilities. 
     Electronic devices use satellite navigation systems to support navigation functions. For example, an electronic device may use a satellite navigation system such as the Global Positioning System (GPS) to obtain position information, timing information, and other navigation information. The Global Positioning System includes satellites that orbit the Earth, Earth-based control and monitoring stations, and GPS receivers that are located within the electronic devices. GPS services may be provided on a continuous basis anywhere that is within range of the orbiting satellites. 
     A portable electronic device may include a GPS receiver. The GPS receiver is used to determine the current position (location) of the portable electronic device. During operation, the GPS receiver may receive data streams from GPS satellites orbiting the Earth. Using a local clock, the GPS unit analyzes each data stream to make a transit time and distance estimation. 
     A method known as geometric trilateration may be used to determine the location of the electronic device by analyzing the estimated distances of each of the satellites relative to the GPS receiver. It may be desirable to characterize the performance of the GPS receiver to determine whether the GPS receiver satisfies design criteria during normal wireless operation. 
     Conventional arrangements for testing GPS receiver performance involve placing an electronic device under test (DUT) within a test chamber and using a single test antenna within the test chamber to transmit GPS signals to the GPS receiver. The test antenna transmits the GPS signals at a selected power level. If the signal strength of GPS signals being received at the GPS receiver exceeds a predetermined threshold level, the GPS receiver satisfies design criteria. If the signal strength of the GPS signals being received at the GPS receiver is less than the predetermined threshold level, the GPS receiver fails to satisfy design criteria. Testing GPS performance using only one antenna, however, does not accurately characterize the behavior of the GPS receiver in a real world environment (i.e., a real world environment in which multiple GPS satellites simultaneously transmit radio-frequency signals to the GPS receiver). 
     It would therefore be desirable to be able to provide improved ways for testing satellite navigation system receiver performance. 
     SUMMARY 
     A radio-frequency test system for testing a wireless electronic device is provided. The electronic device currently being tested may be referred to as a device under test (DUT). The DUT may contain wireless communications circuitry such as a cellular telephone transceiver, a local area network transceiver, and a satellite navigation system receiver. The test system may be used to characterize the performance of the satellite navigation system receiver. 
     The test system may include a test host, a satellite navigation system simulator, a test chamber, and multiple test antennas within the test chamber. A DUT may be attached to a DUT holder within the test chamber during testing. The DUT holder may be configured to rotate the DUT during testing. The satellite navigation system simulator may receive at least ephemeris and almanac data and may generate corresponding radio-frequency test signals based on the supplied ephemeris and almanac data. The test signals may be radiated over the air to the DUT via the test antennas. 
     The test antennas may be mounted on antenna mounting structures positioned within the test chamber. The antenna mounting structures may be ring-shaped support structures to which the test antennas can be mounted. Test antennas associated with each antenna mounting structure may form a circular antenna array that serve to emulate the behavior of satellites associated with a respective orbital plane in a given satellite constellation (e.g., each test antenna may be placed in a desired position relative to the DUT and may radiate simulated signals that are similar to signals that would have been broadcast by the satellite that is being emulated by that test antenna). The antenna mounting structures may be fixed or rotated during testing. The test host may be used to control the orientation of the DUT, the movement of the antenna mounting structures, and operation of the satellite navigation system emulator  204  during test operations. 
     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 schematic diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram of a conventional test system for testing satellite navigation system receiver performance. 
         FIG. 3  is a diagram of an illustrative test system that includes multiple test antennas and that is used for characterizing satellite navigation system receiver performance in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram of an illustrative device under test (DUT) positioner in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram of an illustrative rotatable antenna mounting structure for supporting the multiple test antennas of  FIG. 3  in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagram of multiple rotatable antenna mounting structures in accordance with an embodiment of the present invention. 
         FIG. 7  is a diagram of multiple antenna mounting structures rotatable about a common rotational axis in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagram of a spherical test antenna support matrix on which the multiple test antennas of  FIG. 3  can be mounted, where each of the multiple test antennas may be selectively activated in accordance with an embodiment of the present invention. 
         FIG. 9  is a flow chart of illustrative steps involved in operating the test system of  FIG. 3  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention relate to techniques for testing the performance of satellite navigation receivers in electronic devices. Electronic devices such as portable electronic devices and other electronic equipment may be used to provide navigation services. Such types of electronic devices may include 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, a media player, etc. Electronic devices with satellite navigation capabilities may provide a user with reliable positioning and timing services (e.g., to support navigation applications, games, applications with maps, and other location-based settings). 
     A schematic diagram of an electronic device such as electronic device  10  is shown in  FIG. 1 . As shown in  FIG. 1 , electronic device  10  may include 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 . This 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 (WLAN) 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, etc. 
     Circuitry  28  may be configured to implement control algorithms that control the use of antennas in device  10 . For example, to support antenna diversity schemes and MIMO schemes or beam forming or other multi-antenna schemes, circuitry  28  may perform signal quality monitoring operations, sensor monitoring operations, and other data gathering operations and may, in response to the gathered data, control which antenna structures within device  10  are being used to receive and process data. As an example, circuitry  28  may control which of two or more antennas is being used to receive incoming radio-frequency 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, etc. 
     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  35 , transceiver circuitry such as transceiver circuitry  36  and  38 , and antenna circuitry  40 . Satellite navigation system receiver  35  may be used to support satellite navigation services such as United States&#39; Global Positioning system (GPS) (e.g., for receiving satellite positioning signals at 1575 MHz), Russia&#39;s Global Navigation Satellite System (GLONASS) (e.g., for receiving satellite positioning signals at 1602 MHz), China&#39;s Compass also known as the Beidou Global navigation system (e.g., for receiving satellite positioning signals at 1561 MHz), Europe&#39;s Galileo positioning system (e.g., for receiving satellite positioning signals at 1164 MHz), and/or other satellite navigation systems. 
     Transceiver circuitry  36  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  36  may sometimes be referred to as wireless local area network (WLAN) transceiver circuitry (to support WiFi® communications) and Bluetooth® transceiver circuitry. Circuitry  34  may use cellular telephone transceiver circuitry (sometimes referred to as cellular radio)  38  for handling wireless communications in cellular telephone bands such as bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz or other cellular telephone bands of interest. 
     Examples of cellular telephone standards that may be supported by wireless circuitry  34  and device  10  include: the Global System for Mobile Communications (GSM) “2G” cellular telephone standard, the Evolution-Data Optimized (EVDO) cellular telephone standard, the “3G” Universal Mobile Telecommunications System (UMTS) cellular telephone standard, the “3G” Code Division Multiple Access 2000 (CDMA 2000) cellular telephone standard, and the “4G” Long Term Evolution (LTE) cellular telephone standard. Other cellular telephone standards may be used if desired. These cellular telephone standards are merely illustrative. 
     Wireless communications circuitry  34  may include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry  34  may include wireless circuitry for receiving radio and television signals, paging circuits, etc. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 
     Wireless communications circuitry  34  may include antennas  40 . Antennas  40  may be formed using any suitable antenna types. For example, antennas  40  may include antennas with resonating elements that are formed from loop antenna 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 and another type of antenna may be used in forming a remote wireless link. 
     Satellite navigation system receiver  35  may receive radio-frequency signals from an associated group of satellites  12  such as satellites  12  orbiting the Earth. Each group of satellites operating in concert to provide coordinated ground coverage may be referred to collectively as a satellite constellation. For example, the GPS constellation may include a first set of at least 24 satellites that are evenly distributed among six different orbital planes. As another example, the GLONASS constellation may include a second set of at least 24 satellites (i.e., satellites different than the first set of GPS satellites) that are equally distributed among three different orbital planes. In general, a satellite constellation may include any suitable number of associated satellites distributed among any number of orbital planes. Receiver  35  may be configured to calculate its position by precisely timing the signals that are being transmitted by associated satellites  12 . For example, each GPS satellite  12  may continuously broadcast signals to receiver  35 . The broadcasted signals may include information such as the time the signals were sent, relevant orbital information (e.g., the precise location of each satellite), and other related information. 
     Receiver  35  may receive the broadcasted satellite information. Receiver  35  may analyze the times at which the signals are received. Receiver  35  may calculate the transit time for each received signal based on measured timing information. The transit time of each message may be multiplied by the speed of light (e.g., the speed at which wireless signals propagate through air) to compute the distance between user device  10  and each corresponding navigation system satellite  12 . 
     Geometric trilateration techniques may then be used to combine the computed distances with the GPS satellites&#39; current locations to determine the position (location) of receiver  35 . Receiver  35  may feed the obtained location data to storage and processing circuitry  28 . The process of obtaining the current location of device  10  is sometimes referred to as obtaining a satellite navigation system fix (or a location fix). In addition to determining the current location, receiver  35  may provide time-to-fix (TTF) data (e.g., data indicating the amount of time it takes for receiver  35  to acquire an updated location fix). Satellite navigation system receiver  35  may also be used to obtain other useful location information such as the altitude, direction, and speed of device  10 . 
     As shown in  FIG. 1 , device  10  may also communicate with a base station such as base transceiver station  14 . In particular, radio-frequency signals may be conveyed between cellular telephone transceiver circuitry (cellular radio)  38  and base station  14  during a phone call (as an example). 
     Satellite navigation system receiver  35  and other electrical components within device  10  may be manufactured using state of the art semiconductor fabrication processes. Each manufactured part may, however, suffer from process variation. During device assembly, workers and automated assembly machines may be used to form welds, machine features into conductive device structures, connect connectors for antennas and other components to mating connectors, and otherwise form and interconnect electronic device structures within device  10 . If care is not taken, faults may result that can impact the performance of a final assembled device. Process variation, assembly faults, the design of receiver  35 , the isolation of receiver  35  from other device components, and/or other device operating factors can impact the performance of receiver  35  during normal user operation. It may therefore be desirable to test the satellite navigation system receiver performance of device  10  to determine whether receiver  35  satisfies design criteria. 
       FIG. 2  is a diagram of a conventional test system  100  for testing the satellite navigation system performance of device  10 . Device  10  that is currently being tested may be referred to as a device under test (DUT). As shown in  FIG. 2 , test system  100  includes a signal generator  102 , a test chamber  104  in which DUT  10  is placed during testing, and a test antenna  106  positioned within test chamber  104 . Test antenna  106  is connected to an output port of signal generator  102 . 
     Signal generator  102  is configured to generate test signals. The test signals are fed to antenna  106  via a coaxial cable  108 . The test signals are then transmitted over the air using antenna  106  to receiver  35  within DUT  10 . Data can then be gathered from DUT  10  to determine whether receiver  35  is operating satisfactorily. Performing testing by transmitting wireless test signals to DUT  10  within an enclosed chamber is sometimes referred to as “over-the-air” testing. Testing the performance of receiver  35  in this way, however, may not yield accurate results. During real world scenarios, receiver  35  does not only receive signals from a single wireless source but receives signals from multiple wireless signal sources (i.e., device  10  simultaneously receives radio-frequency signals from multiple navigation system satellites during normal user operation). 
     During product design verification, many wireless devices (e.g., hundreds, thousands, or more of DUTs  10 ) may be tested in a test system such as test system  200  of  FIG. 3 . Test system  11  may include testers, tester control boxes, test accessories, computers, network equipment, cabling, test chambers with antennas, and other test equipment for transmitting and/or receiving radio-frequency test signals and gathering test results. 
     An example, test system  200  may include a test host such as test host  202  (e.g., a personal computer), a tester such as satellite navigation system emulator  204 , and a test chamber such as test chamber  206 . Test chamber  206  may have a cubic structure (six square walls) or a rectangular prism-like structure (six rectangular walls), if desired. Test chamber  206  may be internally lined by absorbent material. The absorbent material may be formed from rubberized pyramid-shaped foams or other suitably lossy material. Test chamber  206  may sometimes be referred to as an anechoic chamber. If desired, reverberation chambers (e.g., chambers with one or more tuners that can be moved to different orientations to obtain varying spatial distribution of electrical and magnetic field strength) may also be used. 
     Test chambers  206  may each include multiple antennas such as antennas  208  mounted inside chamber  206 . Antennas  208  may sometimes be referred to as test antennas, test chamber antennas, or over-the-air (OTA) antennas. Antennas  208  may, for example, be patch antennas, spiral antennas, horn antennas, or other types of antennas. Test chamber  206  may therefore be referred to as a multi-antenna test chamber, because test chamber  206  contains more than one antenna. In the example of  FIG. 3 , only three antennas  208  are shown. If desired, less than three, more than three, at least 10, at least 24, or at least 50 test antennas  208  may be mounted within test chamber  206 . 
     During testing, DUT  10  may be placed inside test chamber  206  while test antennas  208  radiate radio-frequency test signals to antennas  40  of DUT  10  (e.g., antennas  40  that are switchably coupled to satellite navigation system receiver  35 ). In particular, DUT  10  may be attached to a positioner such as positioner  212  when DUT  10  is placed within test chamber  206 . Positioner  212  may be a computer-controlled or manually-controlled positioning device that can be used to change the position and orientation of DUT  10  within test chamber  206  during testing. For example, positioner  212  may include actuators for controlling lateral and/or rotational movement of DUT  10  and may therefore sometimes be referred to as a DUT rotator. DUT rotator  212  may be controlled using control signals generated by test host  202  routed over path  213 . 
     Tester  204  may be operated directly or via computer control (e.g., when tester  204  receives commands from test host  202 ). When operated directly, a user may control tester  204  by supplying commands directly to the tester using the user input interface of the test unit. For example, a user may press buttons in a control panel on the tester while viewing information that is displayed on a display in the tester. In computer controlled configurations, a test host such as computer  202  (e.g., software running autonomously or semi-autonomously on the computer) may communicate with the tester (e.g., by sending and receiving data over a wired path  203  or a wireless path between the computer and the tester). 
     Tester  204  may be a tester of the type that is sometimes referred to as a test box or a radio communications tester. Tester  204  may be used to perform radio-frequency signaling tests for a variety of different radio-frequency communications bands and channels. In one suitable embodiment of the present invention, tester  204  may be a satellite navigation system emulator. Emulator  204  may be capable of receiving ephemeris data, almanac, and other navigation information from a user (e.g., settings that are supplied by a test operator). 
     The ephemeris data may include information indicating the precise orbital position of each satellite  12  in a given constellation. During normal device operation, each satellite in a given constellation may transmit respective ephemeris data to receiver  35  so that a position fix can be accurately calculated. A position fix may not be computed until receiver  35  obtains ephemeris data from at least a certain number of satellites in the given constellation. Because the ephemeris information is considered high resolution, the ephemeris information is typically valid for, as an example, no more than four hours after broadcast and needs to be regularly updated (e.g., ephemeris should be updated at least once every four hours). 
     Whereas the ephemeris data contains highly precise information, the almanac includes coarse orbital and status information reflective of the arrangement of an entire satellite constellation. Because the almanac information is considered to be lower resolution, the almanac can be valid for up to 180 days and may be updated on a substantially less frequent basis relative to the ephemeris. The almanac data is typically used during device start-up to help receiver  35  determine which satellites are currently visible based on the last stored location of device  10  and where each of the visible satellites are approximately located. Once receiver  35  detects the visible satellites, receiver  35  retrieves corresponding ephemeris data to acquire a location fix. The almanac is typically not used to compute the actual position of device  10 . A location fix may be calculated entirely based on the ephemeris data received from detected satellites  12 . 
     As satellites  12  in a given satellite constellation orbit the Earth, the precise configuration of the given constellation at any given point in time can be described by associated ephemeris and almanac data. For example, a table containing ephemeris and almanac data may be provided that describes the precise position of each satellite  12  in a given constellation at any point in history (including all past and present configurations). Because the orbital patterns of satellites  12  are well known, ephemeris and almanac information describing the precise configuration of the given constellation at any future point in time can be predicted and tabulated. In other words, it is possible to obtain ephemeris and almanac data that describes the precise configuration of any existing satellite constellation (e.g., the GPS satellite constellation, the GLONASS satellite constellation, etc.) at a selected moment in history, at the present moment, or any a desired point in the future. 
     In one suitable arrangement, test host  202  may provide ephemeris data, almanac data, and other raw data to satellite navigation system emulator  204  so that emulator  204  can generate simulated radio-frequency signals that would have been broadcast to DUT  10  at a selected point in time in a particular location. For example, test host  202  may provide a first set of ephemeris and almanac data during a first test iteration to emulator  204  so that emulator  204  can simulate satellite signals that device  10  received on Mar. 1, 2012 at 11:00 PM if device  10  were located in Tokyo, Japan. As another example, test host  202  may provide a second set of ephemeris and almanac data during a second test iteration to emulator  204  so that emulator  204  can simulate satellite signals that device will receive on Dec. 14, 2015 at 08:45 AM if device  10  were located in Los Angeles, Calif. These simulated satellite signals may be fed to respective test antennas  208  within test chamber  206  so that each test antenna serves as one satellite  12  in a given constellation. Emulator  204  may therefore sometimes be referred to as a satellite navigation system simulator. 
     DUT  10  need not be secured in a fixed orientation within test chamber  206  and may be mounted on a movable support structure  212  (see, e.g.,  FIG. 4 ). DUT  10  may be rotated using structure  212  to emulate potential movement of device  10  during normal user operation as the user handles device  10 . As shown in  FIG. 4 , DUT  10  may be rotated in multiple directions. Structure  212  may include a movable base structure such as base  220 , a first rod structure  222  that is attached to base  220 , a second rod structure  224  that is attached to first rod structure  222 , and a DUT holder  250 . Base  220  may be stationed at any desired location within test chamber  206 . Rod  222  may be oriented perpendicular to base  220 , whereas rod  224  may be oriented perpendicular to rod  222  and parallel to base  220  (as an example). DUT holder  250  may latch on to DUT  10  during testing. 
     Using a motor or other positioning equipment that is part of structure  212 , rod  222  may be rotated about rotational axis  230  in the direction of arrow  232  and may be vertically adjusted in the direction of arrow  238 . Rod  224  may similarly be rotated about rotational axis  226  in the direction of arrow  228  and may be laterally adjusted in the direction of arrow  240 . DUT  10  may also be rotated about rotational axis  234  in the direction of arrow  236  using DUT holder  250 . Rotating DUT  10  about three orthogonal axes in this way may allow test system  200  to gather data for a variety of desired beam angles. If desired, DUT  10  may be fixed in place so there is no rotational or translational movement during testing. The movable DUT support structure  212  of  FIG. 4  is merely illustrative and does not serve to limit the scope of the present invention. If desired, other suitable positioning equipment may be used to rotate and shift DUT  10  within test chamber  206  during over the air (OTA) testing. 
     It may be desirable to physically orient test antennas  208  within test chamber  206  in a way that partially emulates the geometric configuration of satellites  12  in a real world scenario. In one suitable arrangement of the present invention, test antennas  208  may be mounted on a ring-shaped antenna mounting structure  300  (see, e.g.,  FIG. 5 ). It may be desirable to form some or all of support structure  300  from dielectric materials to ensure radio-frequency transparency. 
     As shown in  FIG. 5 , test antennas  208  may be attached to the ring-shaped antenna mounting structure  300  to form a circular antenna array. For example, 24 test antennas  208  may be mounted on structure  300  in an equally distributed arrangement. Each pair of test antennas  208  may be separated by absorbent material  304  that is used to minimize reflections and to provide electromagnetic isolation among the different radiating antennas  208 . 
     Antenna mounting ring  300  may be suspended using motorized positioning equipment  302 . Equipment  302  may include mechanical devices (e.g., motors, pulleys, gears, etc.) that can be used to raise or lower the position of structure  300 , to rotate structure  300  about axis  306 , or to rotate structure  300  in any desired manner (as shown by arrows  310 ). Ring structure  300  may or may not be rotated during testing. In either scenario, DUT  10  should remain substantially within ring structure  300  during testing (e.g., within region  307  as illustrated in  FIG. 5 ). In general, antenna mounting structure  300  may have any other suitable planar two-dimensional shape (e.g., a rectangular mounting structure shape on which a rectangular array of OTA test antennas may be mounted, an elliptical mounting structure shape on which an elliptical array of OTA test antennas may be mounted, a triangular mounting structure shape on which a triangular array of OTA test antennas may be mounted). 
     In another suitable arrangement, multiple ring-shaped test antenna mounting structures may be positioned within test chamber  206  (see, e.g.,  FIG. 6 ). As shown in  FIG. 6 , a first antenna mounting structure  300 - 1  and a second antenna mounting structure  300 - 2  may be positioned within test chamber  206 . The lateral/rotational movement of structure  300 - 1  may be controlled using first positioning equipment  302 - 1 , whereas the lateral/rotational movement of structure  300 - 2  may be controlled using second positioning equipment  302 - 2 . First structure  300 - 1  may have a first diameter D 1  while second structure  300 - 2  may have a second diameter D 2  that is different than D 1 . If desired, the diameters of structures  300 - 1  and  300 - 2  may be equal. 
     Test antennas  208  mounted on structure  300 - 1  may serve to emulate navigation system satellites associated with a first orbital plane in a given constellation, whereas test antennas  208  mounted on structure  300 - 2  may serve to emulate navigation system satellites associated with a second orbital plane in the given constellation. Test antennas  208  may not only be physically positioned to emulate the spatial configuration of a given satellite constellation but may also be configured to radiate simulated test signals similar to signals that would have been transmitted by satellite  12  in that corresponding position in the given satellite constellation. Configured in this way, DUT  10  is tested in a controlled, repeatable setting that is similar to real-world environments (at least from the perspective of DUT  10 ). 
     If desired, at least three ring-shaped antenna mounting structures  300  (each of which includes eight test antennas  208 ) may be used to emulate the GLONASS orbital planes or at least six ring-shaped antenna mounting structures  300  (each of which includes four test antennas  208 ) may be used to emulate the GPS orbital planes, as examples. 
     In general, test chamber  206  may include any number of antenna mounting structures  300 , each of which includes any desired number of test antennas  208 , each of which is controlled using associated positioning equipment  302 , and each of which has any suitable diameter. If desired, antenna mounting structures  300  may be configured in fixed positions during testing. Whether or not structures  300  are fixed or moving during testing, test antennas  208  on a particular antenna mounting structure can be selectively activated (e.g., any desired portion of test antennas  208  that serves as part of a common orbital plane may be switched into use while other antennas positioned in that orbital plane are turned off). Each antenna  208  may be configured to radiate appropriate satellite test signals that are generated using emulator  204  based on the user-supplied ephemeris and almanac data. 
     In another suitable arrangement, multiple ring-shaped antenna mounting structures  300  of varying sizes may be used to form a spherical antenna mounting structures (see, e.g.,  FIG. 7 ). Each of the multiple ring-shaped antenna mounting structures  300  may be lined by absorbers. Test antennas  208  may be embedded in the absorbers. Antenna mounting structures  300  may be individually or collectively rotated about axis  320  in the direction of arrow  322  using positioning equipment  302 . 
     In another suitable arrangement, a spherical test antenna support structure such as structure  400  may be used within test chamber  206  (see, e.g.,  FIG. 8 ). As shown in  FIG. 8 , structure  400  may include a matrix (or mesh) formed from horizontal support members  402  and vertical support members  404 . In general, test antennas  208  may be mounted on any location along a particular member  402  or  404 . In the example of  FIG. 8 , test antennas  208  are positioned such that test antennas  208  are equally distributed throughout structure  400 . A sufficient number of antennas may be used to achieve at least five degrees angular resolution across all possible orbital planes. Radio-frequency test signals may be provided from satellite navigation system emulator  204  to each test antenna  208  via a respective path  406  in downlink direction  408 . 
     Spherical structure  400  may be fixed. The geometric emulation of satellite orbital planes may be achieved by selectively activating desired subsets of antennas  208  mounted on matrix  400 . For example, a first subset of antennas  208  may be activated to emulate satellites associated with a first orbital plane in the GPS constellation, a second subset of antennas  208  may be activated to emulate satellites associated with a second orbital plane in the GPS constellation, etc. Emulator  204  may be capable of outputting test signals to the appropriate test antennas  208 . 
       FIG. 9  is a flow chart of illustrative steps involved in operating test system  200  described in connection with  FIGS. 3-8 . At step  500 , DUT  10  may be placed within test chamber  206  and DUT may be mounted on DUT rotator  212 . Test host  202  may then provide user-supplied almanac and ephemeris information to satellite system navigation emulator  204 . 
     At step  502 , emulator  204  may be used to generate radio-frequency test signals simulated based on the user-supplied almanac and ephemeris information. DUT rotator  212  may also be used to place DUT  10  in a desired starting orientation while antenna mounting structure(s)  300  may be placed in a desired configuration depending on the current satellite constellation under test. For example, antenna mounting structures  300  used to emulate the orbital planes of the GPS constellation may be configured differently than structures  300  used to emulate the orbital planes of the GLONASS constellation. 
     At step  504 , emulator  204  may radiate the test signals to DUT  10  via test antennas  208 . While the simulated satellite test signals are being transmitted from test antennas  208  to receiver  35  of DUT  10 , the position of DUT  10  and the orientation/position of antenna mounting structures  300  may constantly be updated based on predetermined orbital patterns (e.g., based on known or predicated orbiting behavior of satellites  12  over time). 
     At step  506 , DUT  10  may receive the transmitted test signals using receiver  35  and may be configured to automatically compute and store desired signal quality measurements for signals received from each transmitting antenna  208 . Examples of signal quality measurements that may be made in device  10  include 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 (RSSI measurements), channel quality measurements based on received signal code power (RSCP) information (RSCP measurements), channel quality measurements based on signal-to-interference ratio (SINR) and signal-to-noise ratio (SNR) information (SINR and SNR measurements), carrier-to-noise (CNO) ratio, etc. 
     At step  508 , an average of the top five receive signal strengths may be computed (as an example). This average value may be compared to a predetermined threshold. If the average value is greater than the predetermined threshold, satellite navigation system receiver  35  within DUT  10  may be considered to operate satisfactorily according to design criteria. If, however, the average value is less than the predetermined threshold, DUT  10  may be retested or the design of receiver  35  may be revisited to determine the cause of failure. 
     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: 20120413
Publication Date: 20150825
Grant Date: 20150825
Priority Date: 20120413
Inventors: GOEL NISCHAY
JALAHALLI VIVEK K.
CABALLERO RUBEN
VELASCO RICARDO R.
GOPARAJU ANIL KUMAR
Assignee: APPLE INC
CPC Classifications: [{"code": "G01S19/23", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S19/23", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S19/23", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/318", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/318", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 48142994