PATENT DOCUMENT

Publication Number: US-8831529-B2
Application Number: US-201213460718-A
Country: US
Kind Code: B2

Title: Wireless communications circuitry with temperature compensation

Abstract:
A test system for calibrating wireless electronic devices is provided. The test system may include a test host, a radio communication tester, and a temperature chamber in which an electronic device under test (DUT) may be tested. The DUT may include a temperature sensor for monitoring an internal temperature of the DUT and may include power amplifier circuitry for outputting radio-frequency test signals. The tester may be used to measure output power levels of the radio-frequency test signals when the DUT is operating at a given reference temperature and when the DUT is operating at target operating temperature levels other than the given reference temperature. Power amplifier output level offset compensation values may be computed by comparing output power levels measured at each of the target operating temperatures to output power levels measured at the given reference temperature and may be stored in the DUT prior to normal operation.

Claims:
What is claimed is: 
     
       1. A method of using a test system to calibrate an electronic device, wherein the test system includes a radio communication tester and a test chamber in which the electronic device is placed during calibration, the method comprising:
 while the test chamber is set to provide a first a first internal chamber temperature, obtaining baseline measurement data from the electronic device with the radio communication tester; 
 while the test chamber is set to provide a second internal chamber temperature that is different than the first internal chamber temperature, obtaining additional measurement data from the electronic device with the radio communication tester, wherein the electronic device includes wireless communications circuitry configured to generate radio-frequency test signals during calibration, and wherein obtaining the baseline measurement data and the additional measurement data comprises obtaining radio-frequency output power measurements associated with the radio-frequency test signals using the radio communication tester; and 
 computing calibration data for the electronic device by comparing the additional measurement data to the baseline measurement data. 
 
     
     
       2. The method defined in  claim 1 , wherein comparing the additional measurement data to the baseline measurement data comprises computing differences between the additional measurement data and the baseline measurement data. 
     
     
       3. The method defined in  claim 1 , further comprising:
 storing the calibration data in the electronic device, wherein the electronic device is configured to operate in normal user operation using settings based on the stored calibration data. 
 
     
     
       4. The method defined in  claim 1 , wherein the electronic device includes power amplifier circuitry, and wherein the test system further includes a test host, the method further comprising:
 with the test host, configuring the power amplifier circuitry in the electronic device to output radio-frequency test signals using a plurality of radio-frequency gain settings at desired frequencies. 
 
     
     
       5. The method defined in  claim 1 , wherein the test system further includes a power supply unit, the method further comprising:
 with the power supply unit, proving power to the electronic device during calibration; and 
 with the power supply unit, monitoring power consumption levels for the electronic device during calibration. 
 
     
     
       6. The method defined in  claim 1 , wherein the second internal chamber temperature comprises a target temperature level in a list of predetermined target temperatures levels to be calibrated, the method further comprising:
 calibrating the electronic device while setting the test chamber to each target temperature level in the list of predetermined target temperature levels; and 
 computing calibration data for each target temperature level in the list of predetermined target temperature levels. 
 
     
     
       7. The method defined in  claim 1 , wherein the electronic device includes power amplifier circuitry, wherein computing the calibration data for the electronic device comprises computing output power offset compensation values for the power amplifier circuitry, and wherein the output power offset compensation values configure the power amplifier circuitry to output radio-frequency signals at satisfactory levels across different device operating temperatures. 
     
     
       8. The method defined in  claim 1 , wherein the electronic device includes power amplifier circuitry, antenna structures, and a transmission line path interposed between the power amplifier circuitry and the antenna structures, and the method further comprising:
 coupling the radio communication tester to the transmission line path using a radio-frequency test probe, wherein the antenna structures are electrically decoupled from the power amplifier circuitry when the radio-frequency test probe is coupled to the transmission line path. 
 
     
     
       9. A method of using a test system to calibrate an electronic device having a temperature sensing circuit operable to provide a sensor output value, wherein the test system includes a test chamber in which the electronic device is placed during calibration, the method comprising:
 while the test chamber is set to provide a first internal chamber temperature, obtaining a baseline sensor output value using the temperature sensing circuit in the electronic device; and 
 computing target sensor output values for each target calibration temperature level in a predetermined list of target calibration temperature levels based on the baseline sensor output value and a temperature coefficient associated with the temperature sensing circuit, wherein each of the computed target sensor output values specifies a respective value for which the sensor output value generated by the temperature sensing circuit has to match at a corresponding target calibration temperature level in the predetermined list of target calibration temperature levels. 
 
     
     
       10. The method defined in  claim 9 , wherein the temperature sensing circuit comprises a thermistor, and wherein the temperature coefficient associated with the thermistor is a fixed value. 
     
     
       11. The method defined in  claim 9 , further comprising:
 configuring the test chamber to provide a second internal chamber temperature that is different than the first internal temperature; and 
 while the test chamber is configured to provide the second internal chamber temperature, obtaining a measured sensor output value using the temperature sensing circuit. 
 
     
     
       12. The method defined in  claim 11 , wherein the test system further includes a radio communication tester, the method further comprising:
 determining whether the measured sensor output value is sufficiently close to a corresponding one of the target calibration sensor output values; 
 in response to determining that the measured sensor output value is sufficiently close to the corresponding target calibration sensor output value, using the radio communication tester to obtain desired radio-frequency measurements from the electronic device; and 
 in response to determining that the measured sensor output value is not sufficiently close to the corresponding target calibration sensor output value, reconfiguring the test chamber to provide a third internal chamber temperature that is different than the second internal chamber temperature. 
 
     
     
       13. The method defined in  claim 10 , wherein the test system further includes a radio communication tester, the method further comprising:
 while the test chamber is set to provide the first internal chamber temperature, using the radio communication tester to obtain baseline radio-frequency measurements from the electronic device; and 
 while the test chamber is configured such that the sensor output value is sufficiently close to one of the target sensor output values, using the radio communication tester to obtain additional radio-frequency measurements from the electronic device. 
 
     
     
       14. The method defined in  claim 13 , wherein the electronic device further includes wireless communications circuitry, the method further comprising:
 computing calibration data for the wireless communications circuitry by comparing the additional radio-frequency measurements to the baseline radio-frequency measurements. 
 
     
     
       15. A method of operating an electronic device that includes wireless communications circuitry and a temperature sensing circuit, the method comprising:
 storing calibration settings on the electronic device; 
 with the temperature sensing circuit, monitoring an operating temperature for the electronic device; 
 in response to detecting a first operating temperature, configuring the wireless communications circuitry in a first gain mode by supplying at least a portion of the wireless communications circuitry with a first power supply voltage according to the stored calibration settings; and 
 in response to detecting a second operating temperature that is greater than the first operating temperature, configuring the wireless communications circuitry in a second gain mode by supplying the portion of the wireless communications circuitry with a second power supply voltage that is greater than the first power supply voltage according to the stored calibration settings. 
 
     
     
       16. The method defined in  claim 15 , wherein the temperature sensing circuit comprises a thermistor having a constant temperature coefficient. 
     
     
       17. The method defined in  claim 15 , wherein the wireless communications circuitry includes power amplifier circuitry having a given number of amplifier gain stages, and wherein configuring the wireless communications circuitry using the selected gain setting comprises selectively activating at least some of the amplifier gain stages. 
     
     
       18. The method defined in  claim 17 , wherein the electronic device further includes adjustable power supply circuitry, and wherein configuring the wireless communications circuitry using the selected gain setting further comprises providing an adjustable power supply voltage to the power amplifier circuitry with the adjustable power supply circuitry. 
     
     
       19. The method defined in  claim 15 , wherein the wireless communications circuitry includes power amplifier circuitry, wherein storing the calibration settings comprises storing power amplifier output power offset compensation values corresponding to different device operating temperatures, and wherein configuring the wireless communications circuitry using the selected gain setting comprises adjusting the power amplifier circuitry based on a corresponding power amplifier output power offset compensation value to ensure that the power amplifier circuitry is outputting radio-frequency signals at satisfactory signal levels.

Description:
BACKGROUND 
     Electronic devices often contain wireless communications capabilities. For example, portable electronic devices are often provided with wireless local area network (WLAN) communications circuitry, cellular telephone communications circuitry, and satellite navigation system receiver circuitry such as Global Positioning System (GPS) receiver circuitry. Using wireless communications circuits such as these, a user may communicate with local and remote wireless networks and may receive signals from GPS satellites. 
     As an example, a cellular telephone may include cellular telephone transceiver circuitry that is used to make telephone calls. The cellular telephone transceiver circuitry includes power amplifier circuitry that is used to amplify radio-frequency (RF) signals so that the RF signals can be transmitted to a nearby base station. If care is not taken, a change in temperature resulting from operation of the power amplifier circuitry can adversely affect the cellular telephone&#39;s ability to transmit RF signals at desired output power levels. 
     Consider a scenario in which a cellular telephone transmits RF signals to a current serving base station when the cellular telephone has an internal temperature of 40° C. The transmitted signals may be received by the current serving base station at a satisfactory power level of −10 dBm. As the power amplifier circuitry transmits the RF signals to the base station and generates heat in the process, the internal temperature of the cellular telephone may increase over time. When the internal temperature of the cellular telephone reaches 55° C., the radio-frequency signals that are transmitted by the cellular telephone may be received by the current serving base station at an unacceptably low power level of −15 dBm. As shown in this example, a change in the internal temperature of the cellular telephone can degrade the wireless output capability of the cellular telephone. 
     It would therefore be desirable to be able to provide ways for operating a wireless electronic device while taking into account variations in the operating temperature. 
     SUMMARY 
     Electronic devices may include wireless communications circuitry for supporting wireless operation and may also include temperature sensing circuits configured to monitor device operating temperatures. The wireless communications circuitry within an electronic device may, for example, include transceiver circuitry, power amplifier circuitry, and antenna structures. 
     The transceiver circuitry may be used to generate radio-frequency signals. The power amplifier circuitry may be used to amplify the radio-frequency signals so that the radio-frequency signals may be radiated from the antenna structures at sufficiently high output power levels. The performance of the power amplifier circuitry may vary as the device operating temperature changes. 
     Such types of electronic devices may be calibrated using a test system to obtain power amplifier offset compensation values that compensate for the change in power amplifier performance across different device operating temperatures. In one suitable embodiment, the test system may include a test host (e.g., a personal computer), a radio-frequency communications tester (e.g., a universal radio communication tester), a power supply unit, and a test chamber (e.g., a temperature chamber). 
     During calibration, an electronic device under test (DUT) may be placed within the test chamber. The test host may configure the internal temperature of the test chamber to a selected reference temperature. The test host may then configure the DUT to transmit radio-frequency test signals to the radio communication tester (e.g., using different radio-frequency power amplifier gain settings at desired frequencies). The radio communication tester may receive the corresponding test signals and perform desired output power measurements. The output power measurements gathered while the test chamber is set to the reference temperature may serve as baseline output power measurements to which other output power measurements are compared during computation of the power amplifier offset compensation values. The test host may also obtain a temperature sensor output value from the DUT using the temperature sensing circuit. The sensor output value corresponding to the reference temperature may represent a baseline reference sensor output value from which other target device operating temperatures (sometimes referred to as target calibration temperature levels) may be computed. 
     The test host may compute target sensor output values corresponding to each target device operating temperature in a predetermined list of target device operating temperatures using the baseline reference sensor output value and a known temperature coefficient associated with the temperature sensing circuit. The test host may then adjust the temperature chamber so that the DUT is tested at each of the target device operating temperatures (e.g., the radio communication tester may be used to obtain output power measurements while the sensor output values are sufficiently close to the computed target sensor output values). 
     Output power measurements measured in this way may be compared to the baseline output power measurements to determine output power offset values as a function of device operating temperature. Offset values obtained in this way can be stored in the device as calibration data. During normal operation, the electronic device may adjust the wireless communications circuitry using the calibration data so radio-frequency performance is optimized across different device operating temperatures (as detected by the temperature sensing circuit). 
     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 and a temperature sensor in accordance with an embodiment of the present invention. 
         FIG. 2  is a plot of radio-frequency output power level versus radio-frequency gain index associated with the wireless communications circuitry in the electronic device of  FIG. 1  in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram of an illustrative test system that in includes a temperature chamber in which the electronic device of  FIG. 1  can be calibrated in accordance with an embodiment of the present invention. 
         FIG. 4  is a plot of a temperature dependent sensor output value generated by the temperature sensor in the electronic device of  FIG. 1  versus device operating temperature in accordance with an embodiment of the present invention. 
         FIG. 5  is a flow chart of illustrative steps for computing target temperature sensor output values corresponding to respective target device operating temperatures in accordance with an embodiment of the present invention. 
         FIG. 6  is a table showing illustrative test data gathered using at least some of the steps of  FIG. 5  in accordance with an embodiment of the present invention. 
         FIG. 7  is a table of computed target temperature sensor output values in accordance with an embodiment of the present invention. 
         FIG. 8  is a flow chart of illustrative steps for using the test system of the type shown in  FIG. 3  to measure radio-frequency output power levels at each target device operating temperature in accordance with an embodiment of the present invention. 
         FIG. 9  is a table showing illustrative test data gathered using at least some of the steps of  FIG. 8  in accordance with an embodiment of the present invention. 
         FIG. 10  is a flow chart of illustrative steps for computing temperature dependent output power offset compensation values in accordance with an embodiment of the present invention. 
         FIG. 11A  is a plot showing how radio-frequency output power levels measured using the steps of  FIG. 8  may vary as a function of device operating temperature in accordance with an embodiment of the present invention. 
         FIG. 11B  is a plot showing temperature dependent power supply levels that may be supplied to the wireless communications circuitry in the electronic device of  FIG. 1  for compensating radio-frequency output power offsets in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     This relates generally to electronic devices, and more particularly, to electronic devices having wireless communications capabilities. 
     Electronic devices that include wireless communications circuitry may be portable electronic devices such as laptop computers or small portable computers of the type that are sometimes referred to as ultraportables. Portable electronic devices may also be somewhat smaller devices. The wireless electronic devices may be, for example, cellular telephones, media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controllers, global positioning system (GPS) devices, tablet computers, and handheld gaming devices. Wireless electronic devices such as these may perform multiple functions. For example, a cellular telephone may include media player functionality and may have the ability to run games, email applications, web browsing applications, and other software. 
       FIG. 1  shows an illustrative electronic device that includes wireless communications circuitry such as wireless communications circuitry  12 . As shown in  FIG. 1 , wireless communications circuitry  12  may include at least baseband processor  18 , wireless transceiver circuitry  14 , radio-frequency (RF) front end circuitry  19 , and one or more antennas (antenna structures)  34 . Front end circuitry  19  may include power amplifier circuitry  20 , filter circuitry  28 , impedance matching circuitry  32 , and other suitable radio-frequency circuits. During signal transmission operations, transceiver circuitry  14  may supply radio-frequency signals that are transmitted by antennas  34 . During signal reception operations, circuitry  14  may accept radio-frequency signals that have been received by antennas  34 . 
     The antenna structures and transceiver circuits of device  10  may be used to support communications over any suitable wireless communications bands. For example, wireless communications circuitry  12  may be used to cover communications frequency bands such as cellular telephone voice and data bands at 700 MHz, 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and the communications band at 2100 MHz band, the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz (also sometimes referred to as wireless local area network or WLAN bands), the Bluetooth® band at 2.4 GHz, the Global Positioning System (GPS) band at 1575 MHz, and Global Navigation Satellite System (GLONASS) band at 1602 MHz. 
     Device  10  may be used to cover these communications bands and other suitable communications bands with proper configuration of the antenna structures in wireless communications circuitry  12 . Any suitable antenna structures may be used in device  10 . For example, device  10  may have one antenna or may have multiple antennas. The antennas in device  10  may each be used to cover a single communications band or each antenna may cover multiple communications bands. If desired, one or more antennas may cover a single band while one or more additional antennas are each used to cover multiple bands. 
     Device  10  may include storage and processing circuitry such as storage and processing circuitry  16 . Storage and processing circuitry  16  may include one or more different types of storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), volatile memory (e.g., static or dynamic random-access-memory), etc. Storage and processing circuitry  16  may be used in controlling the operation of device  10 . Processing circuitry in circuitry  16  may be based on processors such as microprocessors, microcontrollers, digital signal processors, dedicated processing circuits, power management circuits, audio and video chips, radio-frequency transceiver processing circuits, radio-frequency integrated circuits of the type that are sometimes referred to as baseband modules, and other suitable integrated circuits. 
     Storage and processing circuitry  16  may be used in implementing suitable communications protocols. Communications protocols that may be implemented using storage and processing circuitry  16  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, protocols for handling 2G cellular telephone communications protocols such as GSM (Global System for Mobile Communications) and CDMA (Code Division Multiple Access), 3G cellular telephone communications protocols such as UMTS (Universal Mobile Telecommunications System) and EV-DO (Evolution-Data Optimized), 4G cellular telephone communications protocols such as LTE, etc. 
     Data signals that are to be transmitted by device  10  may be provided to baseband processor  18  (sometimes referred to as a baseband module). Baseband processor  18  may be implemented using a single integrated circuit (e.g., a baseband processor integrated circuit) or using multiple integrated circuits. 
     Baseband processor  18  may receive signals to be transmitted via antennas  34  over path  13  from storage and processing circuitry  16 . Baseband processor  18  may provide signals that are to be transmitted to transmitter circuits within transceiver circuitry  14 . The transmitter circuits may be coupled to radio-frequency power amplifier circuitry  20  via a transmit (TX) path such as path  26 . Path  13  may also carry control signals from storage and processing circuitry  16 . These control signals may be used to control the power of the radio-frequency signals that the transmitter circuits within transceiver circuitry  14  supplies to the input of power amplifiers  20  via path  26 . For example, the control signals may be provided to a variable gain amplifier located inside transceiver circuitry  14  that controls the power of the radio-frequency signals supplied to the input of power amplifiers  20 . This transmitted radio-frequency signal power level is sometimes referred to herein as Pin, because it represents the input power to power amplifier circuitry  20 . 
     During data transmission, power amplifier circuitry  20  may boost the output power of transmitted signals to a sufficiently high level to ensure adequate signal transmission. Filter circuitry  28  may contain a radio-frequency duplexer and other radio-frequency output stage circuitry such as radio-frequency switches and passive elements. Switches may, if desired, be used to switch the wireless circuitry between a transmitting mode and a receiving mode. Duplex filter  28  (sometimes referred to as a duplexer) may be used to route input and output signals based on their frequency. 
     Matching circuitry  32  may include a network of passive components such as resistors, inductors, and capacitors and may be used to ensure that antenna structures  34  are impedance matched to the rest of the wireless communications circuitry. Wireless signals that are received by antenna structures  34  may be passed to receiver circuitry in transceiver circuitry  14  over a receive (RX) path such as path  36 . 
     Each radio-frequency power amplifier (e.g., each power amplifier in power amplifier circuitry  20 ) may include one or more power amplifier stages such as stages  22 . As an example, each power amplifier may be used to handle a separate communications band and each such power amplifier may have three series-connected power amplifier stages  22 . Stages  22  may have power supply terminals such as terminals  24  that receive bias voltages. Bias supply voltage may be supplied to terminals  24  using path  42 . Control signals from storage and processing circuitry  16  may be used to selectively enable and disable stages  22  or to control the gain of individual stages using control path  44 . 
     By enabling and disabling stages  22  selectively and/or adjusting the gain of individual stages separately, the power amplifier may be placed into different power modes. For example, the power amplifier may be placed into a high power mode (sometimes referred to as high gain mode) by enabling all three of power amplifier stages  22  or may be placed into a low power mode (sometimes referred to as low gain mode) by enabling two of the power amplifier stages. Other configurations may be used if desired. 
     For example, a very low power mode may be supported by turning on only one of three gain stages or arrangements with more than three power mode settings may be provided by selectively enabling other combinations of gain stages (e.g., in power amplifiers with three or more than three gain stages). In one suitable embodiment of the present invention, the gain of power amplifier circuitry  20  may be fine-tuned by adjusting a radio-frequency gain index (RGI). Incrementing the gain index may, for example, increase the amount of bias current that is provided to one or more of the stages to increase the gain and/or maximum power output of the power amplifier (e.g., control signals may be provided via path  44  that adjust the amount of bias currents provided to amplifiers  22  over path  42 ). 
       FIG. 2  is a plot showing output power level Pout for signals generated at the output of power amplifier circuitry  20  as a function of RGI. As shown in  FIG. 2 , characteristic curve  200  may represent output power levels for amplifier  20  operating in high gain mode, whereas characteristic curve  202  may represent output power levels for amplifier  20  operating in low gain mode. In this example, Pout may be monotonically increased from 5 dBm to 25 dBm as gain index is swept from 0 to 31 when amplifier circuit  20  is configured in low gain mode. When amplifier circuitry  20  is configured in high gain mode, Pout may be monotonically increased from 10 dBm to 35 dBm as gain index is raised from 0 to 31. The values as shown in  FIG. 2  are merely illustrative. By adjusting the power mode and gain index of the amplifier, the output power capabilities of power amplifier circuitry  20  may be adjusted to maximize efficiency (e.g., for any given output power). 
     Device  10  may include adjustable power supply circuitry such as power supply circuitry  38 . Adjustable power supply circuitry  38  may be controlled by control signals received over control path  40 . The control signals may be provided to adjustable power supply circuitry  38  from storage and processing circuitry  16  or any other suitable control circuitry (e.g., circuitry implemented in baseband module  18 , circuitry in transceiver circuitry  14 , etc.). 
     The performance of wireless communications circuitry  12  may be affected by variations in device operating conditions. Consider a scenario in which device  10  includes a cellular telephone transceiver  14  that is being used to make a voice call (e.g., transceiver  14  is configured to transmit radio-frequency signals to a nearby cell tower). At the beginning of the voice call, the transmitted signals arriving at the nearby cell tower may exhibit satisfactory signal levels. Over time, however, power amplifier circuitry  20  that is being used to amplify the radio-frequency signals generates heat that can cause the internal temperature of device  10  (sometimes referred to as device operating temperature) to rise. As the device operating temperature rises, the efficiency of wireless communications circuitry  12  may be degraded, and signals transmitted from device  10  may no longer be received by the nearby cell tower at satisfactory signal levels (i.e., power amplifier circuitry  20  may experience an output power offset). It may therefore be desirable to have a way of monitoring the internal temperature of DUT  10  and to calibrate the performance of circuitry  12  across different operating temperatures (e.g., to obtain power amplifier output power offset compensation values that take into account variations in device operating conditions). 
     Device  10  may include a temperature sensing circuit such as temperature sensor  100 . The example of  FIG. 1  in which temperature sensor  100  is shown to be part of wireless communications circuitry  12  is merely illustrative. Temperature sensor  100  may, as an example, include a thermistor configured to output Dtemp and a reference clock temperature sensor configured to output temp. For example, temperature sensor  100  may produce a temperature dependent output value Dtemp that is proportional to the device operating temperature and may produce a temperature dependent output value Ctemp that is proportional to the temperature of a reference clock on the device. In one suitable embodiment of the present invention, sensor output value Dtemp may be output in the form of a digital signal. In other suitable embodiments, sensor output value Dtemp may be output in the form of an analog signal. Sensor outputs Dtemp and Ctemp may be fed to storage and processing circuitry  16  via path  102 . 
     Storage and processing circuitry  16  may maintain a table of predetermined control settings or other stored information to be used in controlling power supply circuitry  38 . The table may include a list of bias voltages (Vcc values) that are to be supplied by adjustable power supply circuitry  38  (as an example). Based on the known operating conditions of circuitry  20  such as its current gain settings (e.g., a high power mode or a low power mode), the desired output power value Pout to be produced by power amplifier circuitry  20  (e.g., the output power from amplifier circuitry  20  as measured at its output), the desired transmit frequency, the current device operating temperature as measured using temperature sensing circuit  100 , and based on the values of the predetermined control settings in the table, storage and processing circuitry  16  may generate appropriate control signals on path  40  (e.g., analog control voltages or digital control signals). 
     The control signals that are supplied by storage and processing circuitry  16  on path  40  may be used to adjust the magnitude of the positive power supply voltage Vcc (sometimes referred to as the amplifier bias) that is provided to power amplifier circuitry  20  over path  42  (as an example). In other suitable arrangements, storage and processing circuitry  16  may generate appropriate control signals on path  44  that configure power amplifier circuitry  20  in the desired state. These adjustments may be made during testing and during normal operation of device  10  to help compensate for changes in the performance of wireless communications circuitry  12  across different device operating conditions (e.g., across different operating temperatures as measured by sensor  100 , across different amplifier gain modes/settings, across different operating frequencies, across different radio access protocols, etc.). 
       FIG. 3  is a diagram of an illustrative test system  110  that can be used to calibrate device  10 . Device  10  being tested/calibrated may sometimes be referred to as a device under test (DUT). Test system  110  may include a test host such as test host  112  (e.g., a personal computer), a radio communication tester such as radio communication tester  114 , a power supply unit such as power supply unit  116 , a test chamber such as temperature chamber  118 , control circuitry, network circuitry, cabling, and other test equipment. 
     DUT  10  may be placed within test chamber  118  during testing. Test chamber  118  may include a temperature control unit  120  that is used to regulate the temperature within test chamber  118 . Temperature control unit  120  may be adjusted using control signals provided from test host  112  over path  122 . For example, test host  112  may send first control settings to unit  120  that direct control unit  120  to heat up the internal temperature of chamber  118  to 73° C. As another example, test host  112  may send second control settings to unit  120  that direct unit  120  to cool down the internal temperature of chamber  118  to −9° C. Test chamber  118  may therefore sometimes be referred to as a test oven that provides a controlled user-specified oven temperature. In general, temperature control unit  120  may be configured to precisely set the temperature within test chamber  118  to any desired level. 
     As shown in  FIG. 3 , DUT  10  may be coupled to test host  112  via conducted path  124 . The connection represented by path  124  may be a Universal Serial Bus (USB) based connection, a Universal Asynchronous Receiver/Transmitter (UART) based connection, or other suitable types of connections. Test host  112  may send control signals to DUT  10  over path  124  for directing the operation of DUT  10  during testing. For example, test host  112  may send commands to DUT  10  that configure power amplifier  20  in a selected gain mode, that configure transceiver circuitry  14  to generate radio-frequency signals using desired modulation schemes at desired frequencies, etc. 
     Power supply unit  116  may serve to supply power to DUT  10  during testing via path  130 . In particular, power supply unit  116  can be used to monitor current Isupp that is drawn by DUT  10  during testing. Data reflective of the amount of current Isupp drawn by DUT  10  over time may be provided from power supply unit  116  to test host  112  via path  131 . Monitoring current Isupp in this way ensures that DUT  10  does not consume excessive amounts of power when power amplifier circuitry  20  is operated under high gain settings. Current Isupp data gathered using this approach may also be useful when computing power amplifier output efficiency. 
     Radio communication tester  114  may, for example, be a radio communication tester (e.g., the MT8820 Universal Radio Communication Analyzer available from Anritsu) that is used to perform radio-frequency parametric tests for a variety of different radio-frequency communications bands and channels. DUT  10  may include a conductive member  128  interposed in a transmission line path connecting power amplifier circuitry  20  and antenna structures  34 . Tester  114  may be coupled to conductive member  128  via a radio-frequency test cable  126  (e.g., a coaxial cable). Test cable  126  may make contact with member  128  of DUT  10  via mating radio-frequency connectors, via a test probe, or via other suitable coupling mechanisms. 
     Arranged in this way, antenna structures  34  may be decoupled from the remainder of the wireless communications circuitry while cable  126  is coupled to member  128 , and tester  114  may be used to receive radio-frequency test signals generated at the output of power amplifier circuitry  20 . Tester  114  may be used to analyze the RF test signals received from DUT  10 . Test host  112  may retrieve the analyzed results via path  113 . Test host  112  may then compute calibration values (e.g., temperature dependent power amplifier output offset compensation values) using the retrieved test data. 
     Test system  110  as shown in  FIG. 3  is merely illustrative and does not serve to limit the scope of the present invention. If desired, test system  110  may include other means of controlling and monitoring the operating conditions of DUT  10 , may include other types of radio-frequency test units for measuring the performance of DUT  10 , and may include any other suitable test equipment. 
       FIG. 4  shows a plot of temperature sensor output value Dtemp as a function of temperature. As shown by line  210  in  FIG. 4 , Dtemp may decrease as temperature is increased. For example, a temperature of −30° C. may result in temperature sensor  100  generating a Dtemp of 2788; a temperature of 25° C. may result in temperature sensor  100  generating a Dtemp of 2540; and a temperature of 85° C. may result in temperature sensor  100  generating a Dtemp of 2270. In this example, temperature sensor  100  exhibits a temperature coefficient k of −4.5 (i.e., the slope of line  210  is equal to −4.5). The temperature coefficient k of temperature sensor  100  is generally a known, fixed value. By monitoring output value Dtemp, an accurate reading of the internal temperature of DUT  10  relative to a baseline temperature reading can therefore be obtained. 
     In the example of  FIG. 4 , consider a scenario in which sensor  100  outputs a Dtemp of 2405. If it is known that at a reference temperature of 25° C. corresponds to a baseline Dtemp equal to 2540, it can be determined that the current internal operating temperature of DUT  10  is equal to 55° C. ([2405−2540]/[−4.5]+25). Consider another scenario in which sensor  100  outputs a Dtemp of 2720. Using the known temperature coefficient of sensor  100  and the baseline temperature reading at 25° C., it can similarly be determined that the current internal operating temperature of DUT  10  is equal to −15° C. (([2720−2540]/[−4.5]+25). In other words, once a baseline temperature sensor reading is made at a reference temperature, the internal operating temperature of DUT  10  can be precisely computed using the baseline temperature output and the known temperature coefficient (e.g., the computed temperature values will be accurate relative to the reference temperature). 
     In computing output power offset compensation values for power amplifier circuitry  20 , it may first be desirable to obtain baseline measurements at a selected reference temperature.  FIG. 5  shows illustrative steps for obtaining baseline output power measurements at a reference temperature of 25° C. using test system  110  of the type described in connection with  FIG. 3 . 
     At step  300 , DUT  10  may be placed within temperature chamber  118 . At step  302 , test host  112  may control temperature control unit  120  to set the internal temperature of chamber  118  to the reference temperature of 25° C. At step  304 , DUT  10  may repeatedly record Dtemp and Ctemp measured using temperature sensor  100  while wireless communications circuitry  12  is turned off (e.g., n Dtemp measurements may be stored in circuitry  102  while transceiver circuitry  14  and power amplifier circuitry  20  are in an off state). Ctemp measurements may be used to compute an offset between the internal temperature of DUT  10  and the oven temperature. 
     At step  306 , wireless communications circuitry  12  may be turned on (e.g., transceiver circuitry  14  and power amplifier circuitry  20  may be placed in an active transmission state). At step  308 , test host  112  may configure DUT  10  so that power amplifier circuitry  20  is set to operate in the low gain mode (see,  FIG. 2 ). 
     At step  310 , a radio communication tester  114  may be used to measure the output power level of power amplifier circuitry  20  while sweeping the radio-frequency gain index from RGI MIN  to RGI MAX  (e.g., from 0 to 31). In particular, transceiver  14  may be configured to output radio-frequency test signals using desired modulation schemes (i.e., at different data rates) at desired frequencies (i.e., in different frequency bands and channels). If desired, DUT  10  may again record Dtemp to ensure that the internal temperature of DUT  10  has not changed by an unacceptable amount since step  304  (e.g., m Dtemp measurements may be stored in circuitry  102  after the output power levels have been measured using tester  114 ). 
     At step  312 , test host  112  may configure DUT  10  so that power amplifier circuitry  20  is set to operate in the high gain mode, and tester  114  may be used to measure the output power level of power amplifier circuitry  20  while gain index is swept from RGI MIN  to RBI MAX  (e.g., the operations of step  310  may be repeated for characterizing the output efficiency of circuitry  20  in high gain mode). If desired, DUT  10  may again record Dtemp to ensure that the internal temperature of DUT  10  has not changed by an unacceptable amount since step  310 . 
     At step  314 , wireless communications circuitry  12  may be turned off (e.g., transceiver circuitry  14  and power amplifier circuitry  20  may be placed in the idle mode). At step  316 , test host  112  may be used to compute a target baseline Dtemp for DUT  10  operating under an oven temperature of 25° C. by averaging measured Dtemp values gathered during steps  304 ,  310 , and  312 . At step  318 , target Dtemp values for other target device operating temperature levels may be computed using only the computed baseline Dtemp and the known temperature coefficient k of temperature sensor  100 . 
       FIG. 6  shows a table of illustrative transmit power measurements that can be gathered during step  310  of  FIG. 5 . As shown in  FIG. 6 , TX power levels can be recorded for signals transmitted in radio-frequency channel C 1  in band B 1  while sweeping RGI from 0 to 31, where the transmitted signals are modulated using 8 Phase Shift Keying (8PSK) and Gaussian Minimum Shift Keying (GMSK) digital modulation schemes, and where power amplifier circuitry  20  is configured in low gain mode (i.e., circuitry  20  has a gain mode value of zero). Values Dtemp 1  may represent an average value computed using the n Dtemp measurements obtained at step  304 . Values Dtemp 2  may represent an average value computed using the m Dtemp measurements obtained at step  312 . The transmit power levels measured at the reference oven temperature of 25° C. may represent baseline transmit power levels from which offset compensation values can be computed. 
     The values shown in  FIG. 6  are merely illustrative. In general, test system  110  may be configured to obtain TX power level measurements for any number of radio-frequency channels in any number of radio-frequency bands, for radio-frequency signals transmitted using any desired frequency modulation schemes (e.g., for radio-frequency signals modulated using Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16-QAM), 64-QAM, etc.), and for any number of power amplifier gain settings (e.g., when power amplifier circuitry  20  is configured in a low gain mode, in a high gain mode, or in any intermediate gain modes and when power amplifier circuitry  20  is adjusted across different radio-frequency gain index settings). 
       FIG. 7  is a table that includes target operating temperatures levels and corresponding target sensor output values Dtemp that can be computed during steps  316  and  318  of  FIG. 5 . At step  316 , the target Dtemp corresponding to an operating temperature of 25° C. (i.e., the reference temperature) may be computed by averaging at least Dtemp 1  and Dtemp 2  (see,  FIG. 6 ). The resulting target Dtemp value of 2370 ([2373+2367]/2) as shown in  FIG. 7  may represent the baseline Dtemp from which all other target Dtemp values are computed. 
     The values listed in column  350  may represent a predetermined list of target operating temperatures under which DUT  10  should be calibrated. These values may therefore sometimes be referred to as target calibration temperature levels. The list of target temperature values in  FIG. 7  ranges from −30° C. to 85° C. and is meant to cover a wide range of operating conditions for device  10 . The values listed in column  352  represent incremental changes in temperature from one target operating temperature to the next. The values listed in column  354  may be computed by multiplying the ΔTEMP values of column  352  by the known temperature coefficient k of temperature sensor  100 . In this example, the temperature coefficient k of sensor  100  is equal to −4.0. For instance, the change in Dtemp (ΔDtemp) corresponding to the target temperature of 39° C. may be equal to −56 (14*−4), whereas ΔDtemp corresponding to the target temperature of −15 may be equal to 64 (−16*−4). 
     At step  318  of  FIG. 5 , the target Dtemp values may be calculated by adding the computed ΔDtemp values to the baseline Dtemp value of 2370. For example, the target Dtemp corresponding to the target operating temperature of 70° C. may be equal to 2190 (2370−56−60−64). As another example, the target Dtemp corresponding to the target operating temperature of 1° C. may be equal to 2454 (2370+24+60). Target Dtemp values corresponding to each of the values listed in column  350  may be computed in this way. The values of  FIG. 7  are merely illustrative. In general, the temperature coefficient of sensor  100  may be any positive or negative constant, and target Dtemp values may be computed using this approach for any number (or range) of desired target operating temperatures. 
     Once the target Dtemp values have been computed, test system  110  may be used to measure the TX output power levels for DUT  10  at each of the target operating temperatures. At step  400  of  FIG. 8 , test host may direct temperature control unit  120  to set the temperature within chamber  118  to a selected target temperature other than the reference temperature (e.g., the oven temperature may be set to 39° C.). 
     At step  402 , sensor  100  may be used to measure Dtemp n times. The measured Dtemp values may be fed to test host  112 . Test host  112  may compute an average Dtemp based on the measured Dtemp values. Test host  112  may determine whether the average Dtemp value is sufficiently close the target Dtemp corresponding to the target temperature currently selected for calibration. If the magnitude of the difference between the average Dtemp and the target Dtemp exceeds a predetermined threshold, test host  112  may adjust temperature control unit  120  accordingly until the difference between the average Dtemp and the target Dtemp is less than the predetermined threshold. 
     At step  404 , Dtemp measurements may be read back from DUT  10 , and wireless communications circuitry  12  may be turned on (e.g., transceiver circuitry  14  and power amplifier circuitry  20  may be placed in an active transmission state). At step  406 , test host  112  may configure DUT  10  so that power amplifier circuitry  20  is set to operate in the low gain mode. 
     At step  408 , tester  114  may be used to measure the output power level of power amplifier circuitry  20  while sweeping the radio-frequency gain index from RGI MIN  to RGI MAX  (e.g., from 0 to 31). In particular, transceiver  14  may be configured to output radio-frequency test signals using desired modulation schemes (at different data rates) at desired frequencies (in different frequency bands and channels). If desired, DUT  10  may again record Dtemp to ensure that the internal temperature of DUT  10  has not changed by an unacceptable amount since step  402  (e.g., m Dtemp measurements may be stored in circuitry  102  after the output power levels have been measured using tester  114 ). 
     At step  410 , test host  112  may configure DUT  10  so that power amplifier circuitry  20  is set to operate in the high gain mode, and tester  114  may be used to measure the output power level of power amplifier circuitry  20  while gain index is swept from RGI MIN  to RBI MAX  (e.g., the operations of step  408  may be repeated for characterizing the output efficiency of circuitry  20  in high gain mode). If desired, DUT  10  may again record Dtemp to ensure that the internal temperature of DUT  10  has not changed by an unacceptable amount since step  408 . 
     At step  412 , wireless communications circuitry  12  may be turned off (e.g., transceiver circuitry  14  and power amplifier circuitry  20  may be placed in the idle mode). Processing may loop back to step  400  if there are additional target temperatures levels for which DUT  10  should be calibrated, as indicated by path  414 . 
       FIG. 9  shows a table of illustrative transmit power measurements gathered during step  408  of  FIG. 8 . These values may be measured at the same transmit settings as those described in connection with  FIG. 6  except at a new target operating temperature. Notice that to achieve a target temperature of 39° C., the oven temperature may only be set to 35.4° C. so that Dtemp 1  and Dtemp 2  are sufficiently close to the target Dtemp of 2314 (see,  FIG. 7 ). In general, the TX power levels measured at higher temperatures (e.g., temperatures greater than 25° C.) tend to be lower than the baseline TX power levels measured at 25° C., whereas the TX power levels measured at lower temperatures (e.g., temperatures less than 25° C.) tend to be higher than the baseline power levels measured at 25° C. Test data may be gathered in this way for each of the target operating temperatures using test system  110 . 
     When test data has been gathered for each of the target operating temperatures, the illustrative steps of  FIG. 10  can be performed. At step  500  of  FIG. 10 , test host  112  may be used to compute power amplifier output power offset compensation values for each of the target operating temperatures. The output power offset compensation values may, for example, be calculated by subtracting the measured TX power level associated with each target temperature from the baseline TX power level (i.e., the measured TX power level associated with the reference temperature). As shown in  FIG. 11A , an offset ΔP 1  may be computed for the target operating temperature of 54° C., whereas an offset ΔP 2  may be computed for the target operating temperature of −15° C. (e.g., the amount of offset at each target temperature can be obtained by computing the difference between the measured TX power at each of the target temperatures and the measured TX power at the reference temperature). 
     At step  502 , the computed offset compensation values may be stored in DUT  10  (e.g., the offset compensation values may be burned into non-volatile memory that is part of storage and processing circuitry  16 ). At step  504 , DUT  10  may be configured in signaling mode (e.g., DUT  10  may communicate with a radio communication tester by establishing a protocol-compliant communications link with the radio communication tester) to ensure that DUT  10  is transmitting signals at satisfactory output power levels during normal user operation. 
     Once DUT is loaded with the offset compensation values, DUT  10  may control power amplifier circuitry  20  based on these compensation values while continuously monitoring its operating temperature using temperature sensor  100 . As an example, consider a scenario in which sensor  100  in DUT  10  generates Dtemp indicating that the current operating temperature of DUT  10  is equal to 25° C. DUT  10  may retrieve a corresponding offset compensation value of zero from non-volatile memory  16  and may configure power supply circuitry  38  to supply power amplifier circuitry  20  with a nominal power supply voltage of 1.0 V (see, e.g.,  FIG. 11B ). 
     As another example, consider a scenario in which sensor  100  in DUT  10  generates Dtemp indicating that the current operating temperature of DUT  10  is equal to 54° C. DUT  10  may retrieve a corresponding offset compensation value of −2 (reflective of a power amplifier efficiency degradation) from non-volatile memory  16  and may therefore configure power supply circuitry  38  to supply power amplifier circuitry  20  with a proportionally elevated power supply voltage of 1.1 V. 
     As another example, consider a scenario in which sensor  100  in DUT  10  generates Dtemp indicating that the current operating temperature of DUT  10  is equal to 16° C. DUT  10  may retrieve a corresponding offset compensation value of 1 (reflective of a power amplifier efficiency improvement) from non-volatile memory  16  and may therefore configure power supply circuitry  38  to supply power amplifier circuitry  20  with a proportionally reduced power supply voltage of 0.96 V. Generally, offset compensation values corresponding to temperature levels other than the target operating temperatures may be interpolated or extrapolated based on the measured data. 
     The example described in connection with  FIG. 11B  in which the gain of power amplifier circuitry  20  is adjusted by varying Vcc based on the calibrated offset compensation values is merely illustrative and does not serve to limit the scope of the present invention. If desired, the offset compensation values obtained during calibration operations may be used to adjust the gain of power amplifier circuitry  20  in any suitable fashion by providing appropriate control signals via path  44 . 
     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: 20120430
Publication Date: 20140909
Grant Date: 20140909
Priority Date: 20120430
Inventors: TOH YUPING
LUONG ANH
Assignee: APPLE INC
CPC Classifications: [{"code": "H03G3/3042", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03G3/3042", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03F3/24", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03F3/24", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 49477730