PATENT DOCUMENT

Publication Number: US-8811192-B2
Application Number: US-201113025116-A
Country: US
Kind Code: B2

Title: Methods for testing wireless local area network transceivers in wireless electronic devices

Abstract:
An electronic device may include wireless circuitry such as cellular telephone transceiver circuitry and wireless local area network (WLAN) transceiver circuitry. The telephone transceiver may be used to establish long-range wireless connectivity, whereas the WLAN transceiver may be used to establish short-range wireless connectivity. The performance of the WLAN transceiver may suffer in the presence of heat-generating operations. The performance of the WLAN transceiver may be tested using test equipment while the electronic device is configured in a test mode and a normal user mode. During testing, the WLAN transceiver may be directed to transmit radio-frequency signals while the telephone transceiver is toggled on and off. The test equipment may be used to analyze the radio-frequency signals to measure the transmit power level, transmitter constellation error, transmit spectrum mask, and other performance parameters to determine whether that device under test satisfies design criteria.

Claims:
What is claimed is: 
     
       1. A method of testing a device under test in a test system, wherein the device under test comprises a first wireless transceiver circuit and a second wireless transceiver circuit, the method comprising:
 directing the first wireless transceiver circuit to transmit radio-frequency signals at a desired output power level; 
 while the first wireless transceiver circuit is transmitting radio-frequency signals at the desired output power level and while the second wireless transceiver circuit is rising in temperature as a result of transmitting radio-frequency signals with the first wireless transceiver circuit, directing the second wireless transceiver circuit to transmit test radio-frequency signals; and 
 with a tester, analyzing the test radio-frequency signals. 
 
     
     
       2. The method defined in  claim 1 , wherein analyzing the test radio-frequency signals comprises measuring a performance parameter selected from the group consisting of: a transmit power level, a transmitter constellation error, and a transmit spectrum mask. 
     
     
       3. The method defined in  claim 1 , wherein the first wireless transceiver circuit comprises a cellular telephone transceiver circuit and wherein directing the first wireless transceiver circuit to transmit the radio-frequency signals comprises:
 directing the cellular telephone transceiver circuit to transmit the radio-frequency signals. 
 
     
     
       4. The method defined in  claim 1 , wherein the second wireless transceiver circuit comprises a wireless local area network transceiver circuit and wherein directing the second wireless transceiver circuit to transmit the test radio-frequency signals comprises:
 directing the wireless local area network transceiver circuit to transmit the test radio-frequency signals. 
 
     
     
       5. The method defined in  claim 1 , wherein:
 the first wireless transceiver circuit comprises a cellular telephone transceiver circuit; 
 the second wireless transceiver circuit comprises a wireless local area network transceiver circuit; 
 directing the first wireless transceiver circuit to transmit the radio-frequency signals comprises directing the cellular telephone transceiver circuit to transmit the radio-frequency signals; and 
 directing the second wireless transceiver circuit to transmit the test radio-frequency signals comprises directing the wireless local area network transceiver circuit to transmit the test radio-frequency signals. 
 
     
     
       6. The method defined in  claim 1 , wherein the test system includes a test host and wherein directing the first wireless transceiver circuit to transmit the radio-frequency signals comprises:
 with the test host, directing the first wireless transceiver circuit to transmit the radio-frequency signals at a maximum output power level. 
 
     
     
       7. The method defined in  claim 1 , further comprising:
 turning off the first wireless transceiver circuit to prevent the first wireless transceiver circuit from transmitting radio-frequency signals; and 
 while the first wireless transceiver circuit is turned off and while the second wireless transceiver circuit is falling in temperature as a result of turning off the first wireless transceiver circuit, analyzing the test radio-frequency signals using the tester. 
 
     
     
       8. The method defined in  claim 7 , wherein:
 the device under test comprises a cellular telephone; 
 the first wireless transceiver circuit comprises a cellular telephone transceiver circuit; 
 the second wireless transceiver circuit comprises a wireless local area network transceiver circuit; 
 directing the first wireless transceiver circuit to transmit the radio-frequency signals comprises directing the cellular telephone transceiver circuit to transmit the radio-frequency signals; and 
 directing the second wireless transceiver circuit to transmit the test radio-frequency signals comprises directing the wireless local area network transceiver circuit to transmit the test radio-frequency signals. 
 
     
     
       9. A method of testing a device under test in a test system, wherein the device under test includes a first wireless transceiver circuit and a second wireless transceiver circuit and wherein the test system includes a base station emulator and a wireless local area network circuit, the method comprising:
 directing the first wireless transceiver circuit in the device under test to wirelessly communicate with the base station emulator; 
 while the first wireless transceiver circuit is transmitting radio-frequency signals to wirelessly communicate with the base station emulator and while the second wireless transceiver circuit is rising in temperature as a result of transmitting the radio-frequency signals with the first wireless transceiver circuit, directing the second wireless transceiver circuit to establish a data communications link with the wireless local area network circuit; and 
 while the data communications link is established between the second wireless transceiver circuit and the wireless local area network circuit, performing loopback testing by sending radio-frequency data between the device under test and the wireless local area network circuit. 
 
     
     
       10. The method defined in  claim 9 , wherein the wireless local area network circuit comprises a wireless local area network access point and wherein directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network circuit comprises:
 directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network access point. 
 
     
     
       11. The method defined in  claim 9 , wherein directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network circuit comprises:
 directing the second wireless transceiver circuit to establish a protocol-compliant data communications link between the device under test and the wireless local area network circuit. 
 
     
     
       12. The method defined in  claim 9 , wherein performing loopback testing comprises:
 directing the wireless local area network circuit to transmit test packets to the second wireless transceiver circuit; 
 in response to receiving the test packets from the wireless local area network circuit, transmitting acknowledgement packets to the wireless local area network circuit using the second wireless transceiver circuit; and 
 with the wireless local area network circuit, analyzing the acknowledgement packets transmitted by the second wireless transceiver circuit. 
 
     
     
       13. The method defined in  claim 12 , wherein analyzing the acknowledgement packets comprises measuring a performance parameter selected from the group consisting of: a transmit power level, a transmitter constellation error, and a transmit spectrum mask. 
     
     
       14. The method defined in  claim 9 , wherein the first wireless transceiver circuit comprises a cellular telephone transceiver circuit and wherein directing the first wireless transceiver circuit to wirelessly communicate with the base station emulator comprises:
 directing the cellular telephone transceiver circuit to wirelessly communicate with the base station emulator. 
 
     
     
       15. The method defined in  claim 9 , wherein the second wireless transceiver circuit comprises a wireless local area network transceiver circuit and wherein directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network circuit comprises:
 directing the wireless local area network transceiver circuit to establish the data communications link with the wireless local area network circuit. 
 
     
     
       16. The method defined in  claim 9 , wherein:
 the first wireless transceiver circuit comprises a cellular telephone transceiver circuit; 
 the second wireless transceiver circuit comprises a wireless local area network transceiver circuit; 
 directing the first wireless transceiver circuit to wirelessly communicate with the base station emulator comprises directing the cellular telephone transceiver circuit to wirelessly communicate with the base station emulator; and 
 directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network circuit comprises directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network circuit. 
 
     
     
       17. A method of testing a device under test in a test system, wherein the device under test includes a first wireless transceiver circuit and a second wireless transceiver circuit and wherein the test system includes a base station emulator and a wireless local area network circuit, the method comprising:
 directing the first wireless transceiver circuit in the device under test to wirelessly communicate with the base station emulator; 
 while the first wireless transceiver circuit is transmitting radio-frequency signals to wirelessly communicate with the base station emulator and while the second wireless transceiver circuit is rising in temperature as a result of transmitting the radio-frequency signals with the first wireless transceiver circuit, directing the second wireless transceiver circuit to establish a data communications link with the wireless local area network circuit; and 
 while the data communications link is established between the second wireless transceiver circuit and the wireless local area network circuit, directing the second wireless transceiver circuit to send data to the wireless local area network circuit. 
 
     
     
       18. The method defined in  claim 17 , wherein the wireless local area network circuit comprises a wireless local area network access point and wherein directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network circuit comprises:
 directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network access point. 
 
     
     
       19. The method defined in  claim 17 , wherein directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network circuit comprises:
 directing the second wireless transceiver circuit to establish a protocol-compliant data communications link between the device under test and the wireless local area network circuit. 
 
     
     
       20. The method defined in  claim 17 , wherein directing the second wireless transceiver circuit to send the data comprises directing the second wireless transceiver circuit to send the data at a data rate, the method further comprising:
 receiving the data using the wireless local area network circuit; and 
 with the wireless local area network circuit, obtaining a measured data rate for the received data, wherein the measured date rate is at most equal to the data rate. 
 
     
     
       21. The method defined in  claim 17 , wherein the first wireless transceiver circuit comprises a cellular telephone transceiver circuit and wherein directing the first wireless transceiver circuit to wirelessly communicate with the base station emulator comprises:
 directing the cellular telephone transceiver circuit to wirelessly communicate with the base station emulator. 
 
     
     
       22. The method defined in  claim 17 , wherein the second wireless transceiver circuit comprises a wireless local area network transceiver circuit and wherein directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network circuit comprises:
 directing the wireless local area network transceiver circuit to establish the data communications link with the wireless local area network circuit. 
 
     
     
       23. The method defined in  claim 17 , wherein:
 the first wireless transceiver circuit comprises a cellular telephone transceiver circuit; 
 the second wireless transceiver circuit comprises a wireless local area network transceiver circuit; 
 directing the first wireless transceiver circuit to wirelessly communicate with the base station emulator comprises directing the cellular telephone transceiver circuit to wirelessly communicate with the base station emulator; and 
 directing the second wireless transceiver circuit to establish the data communications link with the wireless local area network circuit comprises directing the wireless local area network circuit to establish the data communications link with the wireless local area network circuit.

Description:
BACKGROUND 
     This invention relates to testing electronic devices and more particularly, to wireless testing of electronic devices using testers and access points. 
     Electronic devices such as cellular telephones, portable computers, handheld media players, and other devices often contain wireless circuitry. The wireless circuitry may, for example, be used to support wireless local area networking (WLAN) functionality. In a typical scenario, a wireless electronic device may support IEEE 802.11 wireless networking standards (sometimes referred to as WiFi®). 
     Wireless test equipment is used to test wireless electronic devices. For example, wireless test equipment is sometimes used to perform WLAN testing. A tester may, for example, perform packet loopback testing. In packet loopback testing, control messages are transmitted from a tester to a device under test (DUT) in the form of a number of test data packets. The control messages instruct the DUT to transmit acknowledgment data packets back to the tester. The acknowledgement data packets transmitted from the DUT are then captured by the tester. The tester analyzes the acknowledgement packets using its built-in analysis capabilities to extract radio-frequency parametric data such as transmit power and transmitter constellation error. 
     As an example, a wireless electronic device such as a cellular telephone may include cellular telephone transceiver circuitry that is used to make telephone calls. The cellular telephone transceiver circuitry contains power amplifier circuitry that transmits radio-frequency (RF) signals to a nearby base station. If care is not taken, a rapid change in heat generated from the power amplifier circuitry may adversely affect the capability of the WLAN circuitry to properly transmit data (i.e., to transmit data having power levels and transmitter constellation errors that satisfy performance criteria). 
     Conventional arrangements for testing WLAN circuit functionality involve measuring the performance of the WLAN circuitry while the power amplifier circuitry is placed in an active mode that constantly transmits radio-frequency signals or in an inactive mode during which the power amplifier is turned off. The performance of the WLAN circuitry, however, may be most adversely affected when the thermal transient (i.e., the instantaneous change in heat generated by the cellular telephone transceiver circuitry) is maximized. Testing WLAN circuitry performance using this conventional approach is not a rigorous test of WLAN circuitry performance, because leaving the power amplifier circuitry in the active or inactive mode does not maximize thermal transient. 
     It would therefore be desirable to be able to provide improved ways of testing WLAN transceiver circuitry performance. 
     SUMMARY 
     An electronic device such as a portable user device may include wireless communications circuitry such as cellular telephone transceiver circuitry, wireless local area network (WLAN) transceiver circuitry (e.g., a transceiver that can support IEEE 802.11 communications standards), satellite navigation system receiver, at least one local oscillator, and other wireless circuitry. The local oscillator may be a crystal oscillator that serves to generate reference clock signals for the different wireless communications circuitry on the electronic device. 
     The user device may be used perform various tasks. For example, the user device may be used to make telephone calls, browse the Internet, run gaming applications, take pictures, etc. Performing these tasks may produce thermal transient that momentarily raises the temperature of the WLAN transceiver circuitry (e.g., WiFi® transceiver circuitry). 
     If, for example, the WiFi® transceiver circuitry suffers from rapid changes in temperature (e.g., if a high temperature gradient is produced on a printed circuit board on which the WiFi® transceiver circuitry is mounted), the WiFi® transceiver circuitry may not function properly. It may be desirable to test WiFi® transceiver performance in the presence of such thermal transient (i.e., heat-inducing) activities. 
     A test system in which a device under test (DUT) is tested may include test equipment such as a base station emulator, a tester, and a test host. The DUT may be configured with a test operating system (e.g., an operating system that lacks a graphical user interface). The base station emulator, the tester, and the DUT may be coupled to the test host during testing. 
     During testing, the DUT may be directed to transmit radio-frequency signals to the tester at a maximum output power level over a non-protocol-compliant link (or over a protocol-compliant link, if desired). The test host may direct the cellular telephone transceiver circuitry to turn on to generate a rising temperature transient profile and to turn off to generate a falling temperature transient profile. The tester may be directed to analyze the radio-frequency signals to measure performance parameters such as transmit output power levels, transmitter constellation errors, transmit spectrum masks, etc. The test host may then be used to determine whether the DUT is a passing device or a failing device based on the measured results. 
     Another test system in which a device under test (DUT) is tested may include test equipment such as a base station emulator, non-signaling tester, signaling tester, an access point, and a test host. The DUT may be configured with a normal user operating system (e.g., an operating system that includes a graphical user interface). The base station emulator, the access point, and the DUT may be coupled to the test host during testing. 
     During testing, the DUT may register with the base station emulator. The DUT may establish a protocol-compliant data link with the signaling tester or access point. Data packets may be conveyed between the access point and the DUT over the protocol-compliant data link. The cellular telephone transceiver circuitry may operate in an active mode to generate a rising temperature transient profile and a sleep mode to generate a falling temperature transient profile. The access point may be directed to analyze the received data packets to measure performance parameters such as transmit output power levels, transmitter constellation errors, transmit spectrum masks, data transfer rate, etc. The test host may then be used to determine whether the DUT is a passing device or a failing device based on the measured results. 
     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 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 an illustrative test system having a non-signaling tester in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram of an illustrative test system having a signaling tester (e.g., an access point) in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram illustrating constellation error in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram illustrating a spectral mask in accordance with an embodiment of the present invention. 
         FIG. 6  is a graph illustrating how the temperature of a wireless local area network transceiver may vary in time as thermal transient operations are performed in accordance with an embodiment of the present invention. 
         FIG. 7  is a graph showing how the wireless local area network transceiver of  FIG. 6  may experience a temperature gradient that varies in time as thermal transient operations are performed in accordance with an embodiment of the present invention. 
         FIG. 8  is a flow chart of illustrative steps involved in performing loopback testing for an electronic device operating in test mode in accordance with an embodiment of the present invention. 
         FIGS. 9 and 10  are flow charts of illustrative steps involved in performing wireless testing for an electronic device operating in normal user mode in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     This relates to perform radio-frequency testing of electronic devices. 
     The electronic devices that is tested may include equipment such as cellular telephones, computers, computer monitors with built in wireless capabilities, desktop computers, portable computers, handheld computers, laptop computers, tablet computers, media players, satellite navigation system devices, and other wireless electronic equipment. An electronic device being tested is typically referred to as a device under test (DUT). 
     Test equipment may be used in performing wireless tests on a device under test. The test equipment may be based on a single test instrument. The test equipment may also be based on multiple pieces of test equipment and associated computers. For example, test systems may be used in which a tester is implemented using one or more networked computers, shared databases, racks of one or more pieces of test equipment, etc. 
     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 such as Global Positioning System (GPS) receiver circuitry  35  (e.g., for receiving satellite positioning signals at 1575 MHz) or GLONASS (e.g., for receiving satellite positioning signals at 1602 MHz), transceiver circuitry such as transceiver circuitry  36  and  38 , and antenna circuitry  40 . 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  38  (sometimes referred to as cellular radio) 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. 
     Wireless communications circuitry  34  may include an oscillator such as crystal oscillator  42 . Crystal oscillator  42  may provide a highly stable local clock that is used as a reference clock signal. As shown in  FIG. 1 , oscillator  42  may feed local clock signals to GPS receiver (or GPS unit)  35 , transceiver circuitry  36 , cellular radio  38 , and other wireless circuits over path  44 . If desired, wireless communications circuitry  34  may include a plurality of oscillators  42 , where each of the plurality of oscillators  42  is used to generate a stable local clock signal for a respective transceiver circuit. GPS receiver  35 , transceiver circuitry  36 , cellular telephone transceiver circuitry  38 , and other wireless circuitry on device  10  may rely on the ability of crystal oscillator  42  to generate precise/accurate control clock signals to operate properly during wireless transmission. 
     As shown in  FIG. 1 , device  10  may communicate with a base station such as base transceiver station (BTS)  14 . In particular, radio-frequency signals may be conveyed between cellular telephone transceiver circuitry  38  (sometimes referred to as cellular radio or cellular telephone radio) and base station  14  during a telephone call (as an example). WLAN circuitry  36  may rely on local clock signals generated by the same oscillator  42  used by cellular telephone circuitry  38  or by a separate oscillator  42  to process radio-frequency signals at desired frequencies during wireless transmission. 
     Device  10  may also communicate with networking equipment such as networking equipment  12  (see, e.g.,  FIG. 1 ). Networking equipment  12  may include wireless access points, routers, switches, bridges, cabling, control circuitry, and other networking equipment. For example, WLAN transceiver circuitry  36  may establish a communications link with network equipment  12 . When the communications link is established, data may be conveyed in the form of packets between circuitry  12  and network equipment  12 . 
     The ability and efficiency of WLAN transceiver circuitry  36  to transmit radio-frequency signals to network equipment  12  at desired performance levels is strongly dependent on the accuracy of crystal oscillator  42 . Even a small error in the clock signals generated by oscillator  42  may result in unacceptable shifts in frequency during signal frequency conversions (e.g., when up-converting signals from baseband to radio frequencies), undesirable reduction in transmit power levels, transmitter constellation errors that exceed design criteria, and other adverse effects. 
     The accuracy of crystal oscillator  42  is generally acceptable during normal operating conditions (e.g., when device  10  is not running processor-intensive applications and is not using heat-producing components). The performance of WLAN transceiver circuitry  36  may, however, be adversely affected by heat-inducing operations on device  10 . For example, a sudden change in temperature (e.g., a high temperature gradient or low temperature gradient) produced as cellular telephone radio circuitry  38  is enabled (or disabled) can cause errors in the clock signals generated using oscillator  42 , thereby resulting in WLAN circuitry performance degradation. It may therefore be desirable to test WLAN transceiver performance in the presence of high/low temperature-gradient-inducing activities. 
     During testing, device  10  may be configured in a test mode, normal user mode, and other modes of operation. Device  10  may be loaded with a test operating system (e.g., an operating system that lacks a graphical user interface) during test mode, whereas device  10  may be loaded with a normal operating system (e.g., an operating system that includes a graphical user interface) during normal user mode. Device  10  configured to operate in the test mode behaves as a passive device that only performs operations upon receiving direct commands from a test host, whereas device  10  configured to operate in the normal user mode behaves as an active device that may automatically perform wireless operations without receiving direct commands from the test host (as an example). 
       FIG. 2  is a diagram showing a test system in which device  10  configured in the test mode can be tested. Device  10  being tested may sometimes be referred to as a device under test (DUT). Test system  50  may include test equipment  52  that is used to test DUT  10 . Test equipment  52  may include base station emulator  54 , non-signaling tester  58 , test host  56 , control circuitry, network circuitry, cabling, and other test equipment. 
     Base station emulator  54  is a device that emulates the behavior of an actual base transceiver station (BTS). Base station emulator  54  may communicate with DUT  10  over a wireless path or over a wired connection in test system  50 . Non-signaling tester  58  may be may be a radio communications tester of the type that is sometimes referred to as a test box or a radio communications tester. Non-signaling tester  58  may, for example, be the non-signaling all-in-one radio communication tester (e.g., a single device that includes a vector signal analyzer and a vector signal generator). Non-signaling tester  58  may be used to perform radio-frequency parametric tests for a variety of different radio-frequency communications bands and channels. DUT  10  may communicate with non-signaling tester  58  over a conducted (as shown in  FIG. 2 ) path or over a wireless path. 
     Base station emulator  54  and non-signaling tester  58  may be coupled to test host  56  (e.g., a personal computer) through line  64 . DUT  10  may be coupled to test host  56  (as indicated by dotted line  60 ) and to non-signaling tester  58  through line  62 . The connection represented by line  60  may be a Universal Serial Bus (USB) based connection, a Universal Asynchronous Receiver/Transmitter (UART) based connection, or other suitable types of connections. 
     During testing, test host  56  may control base station emulator  54  and non-signaling tester  58  by sending commands over line  64  and may control DUT  10  by sending commands over line  60 . DUT  10  may, for example, be directed to transmit radio-frequency signals at a maximum output power level to non-signaling tester  58  using different WLAN protocols (e.g., at 802.11a, 802.11b, 802.11g, 802.11n, etc.), across different channels (e.g., at the 2.4 GHz band, 5 GHz band, etc.), and at different data rates. 
     For example, DUT  10  may be configured to transmit signals using the IEEE 802.11n communications protocol. DUT  10  may transmit signals in different channels in the 2.4 GHz band or the 5 GHz band. DUT  10  may transmit RF signals having a bandwidth of 20 MHz at data rates such as 6.5, 13, 19.5, 26, 39, 52, 58.5, and 65 Mbps and may transmit RF signals having a bandwidth of 40 MHz at data rates such as 13.5, 27, 40.5, 54, 81, 108, 121.5, and 135 Mbps (as examples). If desired, DUT  10  may be configured to transmit RF signals using other communications standards in any channel at any suitable data rate during testing. 
     Non-signaling tester  58  may be used to analyze the RF signals received from DUT  10 . The analyzed results may then be gathered by test host  56 . Test host  56  may be used to determine whether DUT  10  is a passing DUT or a failing DUT depending on the gathered results. 
       FIG. 3  is a diagram showing a test system in which device  10  configured in the normal user mode can be tested. Test system  50  may include test equipment  52  that is used to test DUT  10 . Test equipment  52  may include base station emulator  54 , signaling tester  70 , test host  56 , control circuitry, network circuitry, cabling, and other test equipment. Signaling tester  70  may be a device that allows DUT  10  to connect to a network (e.g., to the Internet) using WiFi® or other WLAN communications standards. DUT  10  may communicate with signaling tester  70  over a conducted (as shown in  FIG. 3 ) path or over a wireless path. Base station emulator  54  and signaling tester  70  may be coupled to test host  56  through line  64 . DUT  10  may be coupled to test host  56  (as indicated by dotted line  60 ) and to signaling tester  70  through line  62 . 
     During testing, test host  56  may control base station emulator  54  and signaling tester  70  by sending commands over line  64  and may control DUT  10  by sending commands over line  60 . Test host  56  may direct signaling tester  70  to broadcast test packets. In response to receiving the test packets broadcast from signaling tester  70 , DUT  10  may transmit acknowledgement packets back to access point  70 . DUT  10  may be configured to transmit packets using different WLAN protocols across different channels at different data rates. 
     For example, DUT  10  may be configured to transmit signals using the IEEE 802.11a communications protocol. DUT  10  may transmit data in different channels in the 5 GHz band. DUT  10  may transmit packets at data rates such as 6, 9, 12, 18, 24, 36, 48, and 54 Mbps (as examples). If desired, DUT  10  may be configured to transmit RF packets using other communications standards in any channel at any suitable data rate during testing. 
     Signaling tester  70  may serve as a spectrum analyzer to analyze the data received from DUT  10 . The analyzed results may then be gathered by test host  56 . Test host  56  may be used to determine whether DUT  10  is a passing DUT or a failing DUT depending on the gathered results. 
     One metric that can be used to determine the quality of the radio-frequency signals transmitted by DUT  10  during testing is transmitter constellation error.  FIG. 4  is a plot that illustrates the constellation error concept. The error vector magnitude or EVM (sometimes referred to as receive constellation error) is a figure of merit for assessing the quality of digitally modulated radio-frequency signals for digital radio transceivers. 
     The radio-frequency signals may be represented by vectors in a complex plane (e.g., an I-Q plane in which the in-phase or I axis is the real axis and the quadrature or Q axis is the imaginary axis). As shown in  FIG. 4 , vector  80  may represent an ideal reference signal. In practice, however, signals transmitted from a radio transceiver may suffer from various implementation non-idealities (e.g., carrier leakage, low image rejection radio, phase noise, etc.) that cause the actual signal to deviate from the ideal locations on the I-Q plane. 
     For example, vector  82  may represent a measured signal. The magnitude error is represented by segment  84 , whereas the phase error is represented by angle θ. The vector difference between ideal signal vector  80  and measured signal vector  82  yields an error vector (see, bolded vector  86  in  FIG. 4 ). The magnitude or length of error vector  86  is defined as the error vector magnitude. EVM is typically expressed in decibels (dB). Different modulation schemes may yield different acceptable levels of EVM. For example, the 16-QAM (Quadrature Amplitude Modulation) scheme may have a maximum allowed EVM of −25 dB, whereas the 64-QAM scheme may have a maximum allowed EVM of −30 dB. 
     Small errors in the clock signals generated by oscillator  42  may cause vector  82  to change in magnitude and/or deviate even further from ideal location X (see, e.g., vector  82 ′ in  FIG. 4 ). Changing the measured signal vector in this way due to oscillator inaccuracy may result in an error vector magnitude that exceeds the maximum allowed EVM. It is therefore desirable to test WLAN circuitry performance in the presence of heat-generating tasks that may cause errors in oscillator  42 . 
     The IEEE 802.11 standards also specify a transmit spectrum mask requirement that defines the permitted power distribution in each channel. A transmit spectrum mask (sometimes referred to as a channel mask or transmission mask) is a set of lines defined to reduce adjacent-channel interference by limiting the amount of power at frequencies beyond a given bandwidth. As shown in  FIG. 5 , spectral mask  90  requires that signals be attenuated by at least 30 dB from its peak power level at ±11 MHz from center frequency fc and attenuated by at least 50 dB from its peak power level at ±22 MHz from center frequency fc (as an example). 
     Characteristic curve  92  may represent a satisfactory transmitted signal power density profile, because each point on curve  92  is below the constraint set by spectral mask  90 . In the example of  FIG. 5 , the channel is effectively 22 MHz wide. The spectral mask defines output power restrictions to ensure that signals stay within their designated channel so that the signals do not leak or interfere with adjacent channels. Small errors in the clock signals generated by oscillator  42  may cause profile  92  to shift in frequency (see, e.g., curve  92 ′ in  FIG. 5 ). Shifting the signal power density profile due to oscillator inaccuracy may result in violation of the spectral mask requirement (e.g., portions of curve  92 ′ exceed the power constraints set by mask  90 ). It is therefore desirable to test WLAN circuitry performance in the presence of heat-generating tasks that may cause errors in oscillator  42 . 
     WLAN transceiver circuitry (e.g., WiFi® transceiver circuitry)  36  may experience performance degradation in the presence of high/low temperature gradients. For example, WiFi® circuitry  36  may transmit radio-frequency signals at insufficient transmit output power levels, excessively high error vector magnitude levels, or insufficient data rates during activation and termination of a heat-inducing operation.  FIG. 6  is a graph showing how the temperature of WiFi® transceiver circuitry  36  (T WIFI ) may vary in time during testing of DUT  10 . At time t 0 , DUT  10  is turned on. DUT  10  may be loaded with a test operating system (e.g., so that the behavior of DUT  10  may be directly controlled using test host  56 ) or may be loaded with a normal user operating system (e.g., DUT  10  may be loaded with default user applications, graphical user interface, etc.). 
     At time t 1 , T WIFI  reaches normal operating temperature T 1 . The time it takes for DUT  10  to power up (e.g., the time period from time t 0  to t 1 ) may be referred to as boot-up time T BOOT . At time t 1 , cellular telephone transceiver circuitry  38  may initiate registration with base station emulator  54  and may begin sending requests to establish a telephone call. At time t 1 , test host  56  may also direct WiFi® transceiver circuitry  36  to establish/authenticate a data communications link with signaling tester  70  (if test setup  50  of  FIG. 3  is used). 
     At time t 2 , DUT  10  may be directed to perform certain tasks that cause internal device circuitry (e.g., storage and processing circuitry  28 , cellular telephone radio  38 , transceiver circuits  36 , etc.) to generate additional heat. For example, a user may want to make a telephone call, start a gaming application, launch a web browser, etc. Different tasks may vary in processing intensity and may cause the peripheral circuitry to generate different heat profiles. 
     Consider a scenario in which DUT  10  is directed to begin cellular transmission by turning on cellular telephone radio  38  at time t 2 . Activating cellular telephone transmission may involve turning on power amplifier circuitry in circuitry  38 . Turning on the power amplifier circuitry may cause temperature T WIFI  to rise rapidly (see, e.g.,  FIG. 6 ). 
     This sudden change in T WIFI  is illustrated in  FIG. 7 .  FIG. 7  is a graph showing the magnitude of the temperature gradient ∥δT WIFI ∥ as a function of time. Temperature gradient is a measure of the instantaneous change in T WIFI . The temperature gradient characteristic curve of  FIG. 7  can be calculated by taking the first derivative of the temperature curve of  FIG. 6  (as an example). As shown in  FIG. 7 , temperature gradient ∥δT WIFI ∥ reaches a peak at gradient level G 1  after time t 2 . The ability of circuitry  36  to transmit radio-frequency signals at desired performance levels may be adversely affected by such high temperature gradient levels. 
     At time t 3 , the temperature-inducing task may be turned off (e.g., cellular radio transceiver  38  may be turned off). Similarly, turning off the power amplifier circuitry in radio  38  may cause temperature T WIFI  to fall. As shown in  FIG. 7 , temperature gradient ∥δT WIFI ∥ reaches a peak at gradient level G 2  after time t 3 . Level G 2  may have the same value as G 1  or may be greater than G 1 . The ability of circuitry  36  to transmit radio-frequency signals at desired performance levels may be adversely affected by such high temperature gradient levels. At time t 4 , cellular telephone transceiver circuitry  38  may be enabled to continue testing circuitry  38 . 
     As shown in  FIG. 6 , WiFi® transceiver circuitry  36  is given a 250 millisecond (ms) time period to transmit radio-frequency signals in response to enabling a heat-inducing task (e.g., from time t 2  to t 3 ) and in response to disable the heat-inducing task (e.g., from time t 3  to t 4 ). If desired, this allotted (predetermined) time period may be less than 250 ms seconds or more than 250 ms. 
     The timing diagrams of  FIGS. 6 and 7  are merely illustrative. The heat experienced by transceiver circuitry  36  during testing may have any suitable temperature profile. 
     Different types of test arrangements may be used during testing of DUT  10 . In one suitable arrangement, DUT  10  may be tested using a “non-signaling” test arrangement. The non-signaling test approach may be suitable for testing DUT  10  configured with a test operating system. In the non-signaling arrangement, test host  56  may direct cellular telephone transceiver circuitry  38  to broadcast radio-frequency signals at a maximum output power level without establishing a protocol-based wireless connection with base station emulator  54  (e.g., base station emulator may not be used during non-signaling testing). 
       FIG. 8  shows steps involved in testing DUT  10  using the non-signaling arrangement (e.g., using test setup  50  of  FIG. 2 ). At step  100 , DUT  10  is powered on in test mode (e.g., DUT  10  is loaded with a test operating system lacking a graphical user interface). At step  102 , test host  56  may select a desired protocol, channel, and data rate for testing. For example, test host  56  may configure circuitry  36  for transmission of radio-frequency signals using the 802.11b protocol in the 2.422 GHz channel (sometimes referred to as channel  3 ) at 5.5 Mbps. 
     At step  104 , test host  56  may direct DUT  10  to transmit RF test signals (e.g., in the form of test packets) to non-signaling tester  58  at a maximum output power level using the settings selected during step  102 . At step  106 , cellular telephone transceiver circuitry  38  may be toggled on or off (e.g., the power amplifier circuitry may be configured to transmit RF signals at maximum output power level or may be turned completely off) to initiate a high temperature gradient-inducing operation. 
     At step  108 , a timer may be started that sets a period of time (e.g., 250 ms) during which DUT  10  transmits test packets to non-signaling tester  58  while T WIFI  is rising/falling. At step  110 , test host  56  may direct non-signaling tester  58  to analyze the test packets received from circuitry  36 . For example, non-signaling tester  58  may be directed to analyze the test packets to measure the transmit power level, transmitter constellation error, and transmit spectrum mask. If desired, other radio-frequency performance metrics such as adjacent channel leakage ratio, signal-to-noise ratio, frequency response, gain, and gain compression may be measured at step  110 . 
     Processing may loop back to step  106  if there are additional test packets to be analyzed (e.g., steps  106 ,  108 , and  110  may be repeated for any suitable number of cycles to gather a sufficient set of measured data), as indicated by path  112 . Processing may loop back to step  102  to perform testing at another setting (e.g., to select another communications protocol, channel, and data rate for testing), as indicated by path  114 . 
     After sufficient data has been gathered across the desired settings (e.g., across the different protocols, bands, channels, data rates, etc.), test host  56  may be used to determine whether DUT  10  is a passing DUT or a failing DUT. For example, if the gathered data exhibits satisfactory transmit power levels, transmitter constellation errors, and/or transmit spectrum masks, DUT  10  may be marked as a passing DUT (step  116 ). 
     If the gathered data exhibits unsatisfactory transmit power levels, transmitter constellation errors, and/or transmit spectrum masks, circuitry  36  fails to satisfy design criteria and DUT  10  is marked as a failing DUT (step  118 ). If desired, DUT  10  may be configured with new design settings (e.g., the distance between cellular telephone radio circuitry  38  and WiFi® transceiver circuitry  36  may be increased to reduce the interference between circuitry  36  and  38  and to further isolate WiFi® circuitry  36  from the heat generated by circuitry  38 ). 
     In another suitable arrangement, DUT  10  may be tested using a “signaling” test arrangement (e.g., using test setup  50  of  FIG. 3 ). The signaling test approach may be suitable for testing DUT  10  loaded with a normal user operating system (e.g., DUT  10  may be loaded with default user applications, graphical user interface, etc.). If desired, DUT  10  may also be configured in the test mode. 
       FIG. 9  shows steps involved in testing DUT  10  using the signaling arrangement. At step  120 , DUT  10  is powered on in normal user mode. At step  122 , test host  56  may select a desired protocol, channel, and data rate for testing. For example, test host  56  may configure circuitry  36  for transmission of radio-frequency signals using the 802.11g protocol in the 2.467 GHz channel (sometimes referred to as channel  12 ) at 54 Mbps. 
     At step  124 , DUT  10  may establish a protocol-compliant data communications link with signaling tester  70 . At step  126 , DUT  10  automatically registers with base station emulator  54  (e.g., DUT  10  notifies base station emulator  54  of its presence). 
     At step  128 , signaling tester  70  may send test packets to DUT  10 . In response to the test packets, circuitry  36  of DUT  10  may send acknowledgement packets back to access point  70 . Sending packets back and forth using this approach may sometimes be referred to as loopback testing. 
     At step  130 , test host  56  may direct base station emulator  54  to begin/terminate a call session. During an active telephone call session, radio circuitry  38  is in an active mode (e.g., cellular radio  38  is actively transmitting radio-frequency signals to base station emulator  54  over the protocol-based wireless connection). When the call session is terminated, cellular radio circuitry  38  is in a sleep mode. The power amplifier circuitry of circuitry  38  may be turned on in the active mode and turned off in the sleep mode. 
     At step  132 , a timer may be started that sets a period of time (e.g., 250 ms) during which data packets are conveyed back and forth between DUT  10  and signaling tester  70 . At step  134 , signaling tester  70  may serve as a spectrum analyzer to analyze the acknowledgement packets received from circuitry  36 . For example, signaling tester  70  may be directed to analyze the test packets to measure the transmit power level, transmitter constellation error, and transmit spectrum mask. If desired, other radio-frequency performance metrics such as adjacent channel leakage ratio, signal-to-noise ratio, frequency response, gain, and gain compression may be measured at step  134 . 
     Processing may loop back to step  130  to perform additional loopback testing (e.g., steps  130 ,  132 , and  134  may be repeated for any suitable number of cycles to gather a sufficient set of measured data), as indicated by path  136 . Processing may loop back to step  122  to perform testing at another setting (e.g., to select another communications protocol, channel, and data rate for testing), as indicated by path  138 . 
     After sufficient data has been gathered across the desired settings (e.g., across the different protocols, bands, channels, data rates, etc.), test host  56  may be used to determine whether DUT  10  is a passing DUT or a failing DUT. For example, if the gathered data exhibits satisfactory transmit performance (e.g., acceptable transmit power levels, transmitter constellation errors, and/or transmit spectrum masks), DUT  10  may be marked as a passing DUT (step  140 ). If the gathered data exhibits unsatisfactory performance levels, circuitry  36  fails to satisfy design criteria and DUT  10  may be reconfigured with new design settings aimed to improve WiFi® transceiver circuitry performance (step  142 , e.g., increase the distance between the WiFi® transceiver and the cellular radio, provide better ground plane to dissipate heat, or add thermal pad). 
     In another suitable signaling test arrangement, DUT  10  may be loaded with a normal user operating system that includes a traffic generating test application. Steps involved in testing this type of DUT are shown in  FIG. 10 . At step  150 , DUT  10  is powered on in normal user mode (e.g., DUT  10  is loaded with a test application operable to generate test traffic at desired data rates). At step  152 , test host  56  may select a desired protocol, channel, and data rate for testing. For example, test host  56  may configure circuitry  36  for transmission of radio-frequency signals using the 802.11n protocol in the 5 GHz band at 150 Mbps. 
     At step  154 , DUT  10  may establish a protocol-compliant data communications link with access point  70 . At step  156 , DUT  10  automatically registers with base station emulator  54  (e.g., DUT  10  notifies base station emulator  54  of its presence). At step  158 , the test application running on DUT  10  may direct WiFi® transceiver circuitry  36  to send a test file to access point  70  at a selected data rate. For example, circuitry  36  may be directed to send a 3 MB test file at a selected data rate of 12 Mbps. Sending the 30 MB test file may therefore take two seconds (3*8/12). 
     At step  160 , test host  56  may direct base station emulator  54  to begin/terminate a call session. During an active telephone call session, radio circuitry  38  is in an active mode (e.g., the power amplifier circuitry in circuitry  38  is turned on). When the call session is terminated, cellular radio circuitry  38  is in a sleep mode (e.g., the power amplifier circuitry in circuitry  38  is turned off). 
     At step  162 , access point  70  may finish receiving the test file from DUT  10  and analyze the data rate at which the test file is received. The analyzed data rate may be stored in test host  56  or in storage and processing circuitry  28  of DUT  10  (as examples). 
     Processing may loop back to step  160  until the test file is completely transmitted, as indicated by path  164 . Processing may loop back to step  152  to perform testing at another setting (e.g., to select another communications protocol, channel, and data rate for testing), as indicated by path  166 . 
     After sufficient data has been gathered across the desired settings (e.g., across the different protocols, bands, channels, data rates, etc.), test host  56  may be used to determine whether DUT  10  is a passing DUT or a failing DUT. For example, if the measured data rate is equal to or sufficiently close to the selected data rate (e.g., if the measured data rate is within one percent of the expected data rate), DUT  10  may be marked as a passing DUT ( 168 ). If the measured data rate is unacceptable lower than the selected data rate (e.g., if the measured data rate is more than one percent less than the expected data rate), circuitry  36  fails to satisfy design criteria and DUT  10  may be reconfigured with new design settings aimed to improve WiFi® transceiver circuitry performance (step  170 ). 
     Steps shown in  FIGS. 8-10  are merely illustrative. These validation techniques may be used to test WiFi® transceiver performance during product design and during production testing. 
     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.

Metadata:
Filing Date: 20110210
Publication Date: 20140819
Grant Date: 20140819
Priority Date: 20110210
Inventors: LUONG ANH
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W52/367", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B17/15", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L1/206", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B17/15", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L1/206", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W24/06", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W24/06", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/0085", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B17/0085", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/367", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 46636793