PATENT DOCUMENT

Publication Number: US-8331883-B2
Application Number: US-26212108-A
Country: US
Kind Code: B2

Title: Electronic devices with calibrated radio frequency communications circuitry

Abstract:
Circuitry for portable electronic devices is provided. The circuitry may include wireless communications circuitry and storage and processing circuitry. The wireless communications circuitry may include an antenna and a radio-frequency power amplifier with an adjustable gain mode. The radio-frequency power amplifier may amplify radio-frequency signals to a given output power. The circuitry may include an adjustable power supply circuit that supplies an adjustable power supply voltage to the power amplifier circuitry. The circuitry may also include a transceiver that produce radio-frequency signals at a specified input power to the power amplifier circuitry. The storage and processing circuitry may be used in storing calibration data. The calibration data may specify adjustments to be made to the input power to the radio-frequency power amplifier, the gain mode setting of the power amplifier, and the power supply voltage for the power amplifier to optimize performance while minimizing power consumption.

Claims:
1. Circuitry on a portable electronic device, comprising:
 a radio-frequency power amplifier that amplifies radio-frequency signals at a given operating frequency that are wirelessly transmitted from the portable electronic device; 
 adjustable power supply circuitry that supplies an adjustable power supply voltage to the radio-frequency power amplifier; and 
 storage and processing circuitry that adjusts the adjustable power supply voltage supplied by the adjustable power supply circuitry to the radio-frequency power amplifier based at least partly on the given operating frequency, wherein the amplified radio-frequency signals are output from the radio-frequency power amplifier at an output power in a communications band subject to adjacent channel leakage ratio requirements and wherein the storage and processing circuitry is configured to store calibration data specifying adjustments that are made to the adjustable power supply voltage as a function of the given operating frequency to minimize the adjustable power supply voltage to conserve power while ensuring that the adjustable power supply voltage has a value equal to or greater than a value such that the amplified radio-frequency signals satisfy the adjacent channel leakage requirements. 
 
     
     
       2. The circuitry defined in  claim 1  wherein the storage and processing circuitry is configured to store calibration data specifying adjustments that are made to the adjustable power supply voltage using the adjustable power supply circuitry as a function of the given operating frequency and as a function of the output power. 
     
     
       3. The circuitry defined in  claim 2  further comprising transceiver circuitry that supplies the radio-frequency signals to an input of the radio-frequency power amplifier at a given input power, wherein the storage and processing circuitry is configured to store calibration data specifying how the given input power is adjusted by the transceiver circuitry as a function of the given operating frequency. 
     
     
       4. The circuitry defined in  claim 3  wherein the radio-frequency power amplifier has an associated gain provided by multiple gain stages and wherein the storage and processing circuitry is configured to store calibration data specifying how the gain is adjusted by selectively enabling the gain stages as a function of desired values of the output power. 
     
     
       5. The circuitry defined in  claim 2  wherein the radio-frequency power amplifier has an associated gain provided by multiple gain stages and wherein the storage and processing circuitry is configured to store calibration data specifying how the gain is adjusted by selectively enabling the gain stages as a function of desired values of the output power. 
     
     
       6. The circuitry defined in  claim 1  further comprising transceiver circuitry that supplies the radio-frequency signals to an input of the radio-frequency power amplifier at a given input power, wherein the storage and processing circuitry is configured to store calibration data specifying how the given input power is to be adjusted by the transceiver circuitry as a function of the given operating frequency. 
     
     
       7. A method for operating a wireless electronic device having at least one antenna, a radio-frequency power amplifier, and an adjustable power supply that supplies the radio-frequency power amplifier with an adjustable power supply voltage, wherein the amplified radio-frequency signals are output from the radio-frequency power amplifier at an output power in a communications band subject to adjacent channel leakage ratio requirements, the method comprising:
 with the radio-frequency power amplifier, amplifying radio-frequency signals at a given frequency to be transmitted through the antenna; and 
 with the adjustable power supply, providing an adjustable power supply voltage to the radio-frequency power amplifier that varies as a function of the given frequency to minimize the adjustable power supply voltage to conserve power while ensuring that the adjustable power supply voltage has a value equal to or greater than a value such that the amplified radio-frequency signals satisfy the adjacent channel leakage requirements; and 
 with storage and processing circuitry, storing calibration data specifying adjustments that are made to the adjustable power supply voltage as a function of the given frequency to minimize the adjustable power supply voltage to conserve power while ensuring that the adjustable power supply voltage has a value equal to or greater than a value such that the amplified radio-frequency signals satisfy the adjacent channel leakage requirements. 
 
     
     
       8. The method defined in  claim 7  wherein the wireless electronic device further comprises transceiver circuitry that supplies the radio-frequency power amplifier with the radio-frequency signals at a given input power, the method further comprising:
 adjusting the given input power with the transceiver circuitry based on frequency-dependent calibration data. 
 
     
     
       9. The method defined in  claim 7  wherein the radio-frequency power amplifier has a gain level established by gain stages in the radio-frequency power amplifier, the method further comprises:
 selectively enabling the gain stages to adjust the gain level based at least partly on a desired output power for the amplified radio-frequency signals. 
 
     
     
       10. The method defined in  claim 7  further comprising:
 with the adjustable power supply, providing the adjustable power supply voltage to the radio-frequency power amplifier based at least partly on a desired output power for the amplified radio-frequency signals. 
 
     
     
       11. The method defined in  claim 10  wherein the wireless electronic device further comprises transceiver circuitry that supplies the radio-frequency power amplifier with the radio-frequency signals at a given input power, the method further comprising:
 adjusting the given input power with the transceiver circuitry based on frequency-dependent calibration data. 
 
     
     
       12. The method defined in  claim 10  wherein the radio-frequency power amplifier has a gain level established by gain stages in the radio-frequency power amplifier, the method further comprises:
 selectively enabling the gain stages to adjust the gain level based at least partly on the desired output power for the amplified radio-frequency signals. 
 
     
     
       13. A portable electronic device, comprising:
 an antenna; 
 a radio-frequency power amplifier that amplifies radio-frequency signals at a given operating frequency that are transmitted from the portable electronic device through the antenna; 
 adjustable power supply circuitry that supplies an adjustable power supply voltage to the radio-frequency power amplifier; and 
 storage and processing circuitry that adjusts the adjustable power supply voltage supplied by the adjustable power supply circuitry to the radio-frequency power amplifier as a function of the given operating frequency, wherein the amplified radio-frequency signals are output from the radio-frequency power amplifier at an output power in a communications band subject to adjacent channel leakage ratio requirements and wherein the storage and processing circuitry is configured to store calibration data specifying adjustments that are made to the adjustable power supply voltage as a function of the given operating frequency to minimize the adjustable power supply voltage to conserve power while ensuring that the adjustable power supply voltage has a value equal to or greater than a value such that the amplified radio-frequency signals satisfy the adjacent channel leakage requirements. 
 
     
     
       14. The portable electronic device defined in  claim 13  wherein the storage and processing circuitry is configured to store calibration data specifying adjustments that are made to the adjustable power supply voltage as a function of the given operating frequency and as a function of the output power. 
     
     
       15. The portable electronic device defined in  claim 14  further comprising:
 transceiver circuitry that supplies the radio-frequency signals to an input of the radio-frequency power amplifier at a given input power, wherein the storage and processing circuitry is configured to store calibration data specifying how the given input power is to be adjusted by the transceiver circuitry as a function of the given operating frequency to produce a desired output power from the radio-frequency power amplifier for all frequencies in a given communications band. 
 
     
     
       16. The portable electronic device defined in  claim 13  further comprising:
 transceiver circuitry that supplies the radio-frequency signals to an input of the radio-frequency power amplifier at a given input power, wherein the storage and processing circuitry is configured to store calibration data specifying how the given input power is to be adjusted by the transceiver circuitry as a function of the given operating frequency. 
 
     
     
       17. The portable electronic device defined in  claim 16  wherein the storage and processing circuitry is configured to store calibration data specifying adjustments that are made to the adjustable power supply voltage as a function of the given operating frequency and as a function of the output power. 
     
     
       18. The portable electronic device defined in  claim 13  further comprising transceiver circuitry that supplies the radio-frequency signals to an input of the radio-frequency power amplifier at a given input power, wherein the storage and processing circuitry is configured to:
 store calibration data specifying how the given input power is to be adjusted by the transceiver circuitry as a function of the given operating frequency; and 
 store calibration data specifying gain mode adjustments and adjustments to the power supply voltage for the power amplifier to conserve power based on required output power levels from the power amplifier circuitry.

Description:
BACKGROUND 
     This invention relates generally to wireless communications circuitry, and more particularly, to wireless communications circuitry with power management capabilities. 
     Handheld electronic devices and other portable electronic devices are becoming increasingly popular. Examples of handheld devices include handheld computers, cellular telephones, media players, and hybrid devices that include the functionality of multiple devices of this type. Popular portable electronic devices that are somewhat larger than traditional handheld electronic devices include laptop computers and tablet computers. 
     Due in part to their mobile nature, portable electronic devices are often provided with wireless communications capabilities. For example, handheld electronic devices may use long-range wireless communications to communicate with wireless base stations. Cellular telephones and other devices with cellular capabilities may communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz. Portable electronic devices may also use short-range wireless communications links. For example, portable electronic devices may communicate using the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz and the Bluetooth® band at 2.4 GHz. Communications are also possible in data service bands such as the 3G data communications band at 2170 MHz (commonly referred to as UMTS or Universal Mobile Telecommunications System band). The use of 3G communications schemes for supporting voice communications is also possible. 
     To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to reduce the size of components that are used in these devices. For example, manufacturers have made attempts to miniaturize the batteries used in handheld electronic devices. 
     An electronic device with a small battery has limited battery capacity. Unless care is taken to consume power wisely, an electronic device with a small battery may exhibit unacceptably short battery life. Techniques for reducing power consumption may be particularly important in wireless devices that support cellular telephone communications, because users of cellular telephone devices often demand long talk times. 
     It is important that power reduction techniques for electronic devices be implemented in a way that allows desired performance criteria be satisfied. As an example, many wireless carriers specify minimum required values for adjacent channel leakage ratio (ACLR). High adjacent channel leakage ratio values are an indicator of poor radio-frequency transmitter performance and must generally be avoided to ensure satisfactory network operation. When minimizing power consumption, it would be advantageous to be able to take into account performance characteristics such as adjacent channel leakage ratio performance characteristics, so that improvements in power consumption performance do not inhibit satisfactory wireless performance. 
     It would therefore be desirable to be able to provide wireless communications circuitry for electronic devices with improved power management capabilities. 
     SUMMARY 
     A portable electronic device such as a handheld electronic device is provided with wireless communications circuitry. The wireless communications circuitry may include a radio-frequency transceiver, a power amplifier that amplifies radio-frequency signals from the transceiver, and an antenna through which the amplified radio-frequency signals may be wirelessly transmitted. The antenna and transceiver may also be used in receiving radio-frequency signals. 
     The portable electronic device may have an adjustable power supply. The power supply may provide a power supply voltage to the power amplifier that helps the portable electronic device satisfy performance constraints such as minimum output power requirements and required levels of adjacent channel leakage ratio. Adjustments may be made to the power supply voltage depending on required output power levels and operating frequency. Adjustments may also be made to the transceiver based on the operating frequency. 
     Storage and processing circuitry in the portable electronic device may be used to store calibration data. The calibration data may be produced during global and individualized calibration tests on the radio-frequency circuitry of the portable electronic device. During operation, calibration data may be used by the storage and processing circuitry to produce control signals for the transceiver, power amplifier, and power supply circuitry that help the electronic device satisfy performance constraints while minimizing power consumption through selective power amplifier power supply voltage and gain reductions. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an illustrative electronic device with wireless communications circuitry having power management capabilities in accordance with an embodiment of the present invention. 
         FIG. 2  is a circuit diagram of illustrative wireless communications circuitry that may be used in an electronic device with wireless communications circuitry power management capabilities in accordance with an embodiment of the present invention. 
         FIG. 3  is a graph showing how an adjustable power supply circuit may provide a radio-frequency power amplifier with different power supply voltages and how different power amplifier gain settings may be used when supplying various amounts of radio-frequency output power in accordance with an embodiment of the present invention. 
         FIG. 4  is a graph showing how adjacent channel leakage ratio characteristics may vary as a function of transmitter frequency in electronic devices using wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 5  is a graph showing how the amount of input power that is required to produce a desired output power with a radio-frequency transmitter power amplifier in an electronic device may vary as a function of frequency in accordance with an embodiment of the present invention. 
         FIG. 6  is a graph of an illustrative radio-frequency power amplifier power supply voltage offset curve that may be used in operating an electronic device in accordance with an embodiment of the present invention. 
         FIG. 7  is a diagram of illustrative characterizing equipment that may be used in measuring radio-frequency performance for electronic devices in accordance with embodiments of the present invention. 
         FIG. 8  is a flow chart of illustrative steps involved in obtaining power supply voltage offset data for use in operating a radio-frequency power amplifier in wireless communications circuitry for a portable electronic device in accordance with an embodiment of the present invention. 
         FIG. 9  is a flow chart of illustrative steps involved in calibrating and using a portable electronic device with power management capabilities in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates generally to wireless communications, and more particularly, to managing power consumption by wireless communications circuitry in wireless electronic devices while satisfying desired performance criteria. 
     The wireless electronic devices may be portable electronic devices such as laptop computers or small portable computers of the type that are sometimes referred to as ultraportables. The wireless electronic devices may also be somewhat smaller devices. Examples of smaller wireless electronic devices include wrist-watch devices, pendant devices, headphone and earpiece devices, and other wearable and miniature devices. With one suitable arrangement, the wireless electronic devices may be portable electronic devices such as handheld electronic devices. 
     The wireless devices may media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controllers, global positioning system (GPS) devices, handheld gaming devices, or cellular telephones. The wireless electronic devices may also be hybrid devices that combine the functionality of multiple conventional devices. An example of a hybrid device is a cellular telephone that includes media player functionality, communications functions, web browsing capabilities, and support for a variety of other business and entertainment applications such as the iPhone® cellular telephones available from Apple Inc. of Cupertino, Calif. These are merely illustrative examples. 
     A schematic diagram of an embodiment of an illustrative wireless electronic device such as a handheld electronic device is shown in  FIG. 1 . Electronic device  10  of  FIG. 1  may be a mobile telephone such as a cellular telephone with media player capabilities, a handheld computer, a remote control, a game player, a global positioning system (GPS) device, a laptop computer, a tablet computer, an ultraportable computer, a combination of such devices, or any other suitable electronic device. 
     As shown in  FIG. 1 , device  10  may include storage and processing circuitry  12 . Storage and processing circuitry  12  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  12  may be used in controlling the operation of device  10 . Processing circuitry in circuitry  12  may be based on processors such as microprocessors, microcontrollers, digital signal processors, dedicated processing circuits, power management circuits, audio and video chips, and other suitable integrated circuits. 
     With one suitable arrangement, storage and processing circuitry  12  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. Storage and processing circuitry  12  may be used in implementing suitable communications protocols. Communications protocols that may be implemented using storage and processing circuitry  12  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 and 3G cellular telephone communications services, etc. 
     Device  10  may have one or more batteries such as battery  14 . To minimize power consumption and thereby extend the life of battery  14 , storage and processing circuitry  12  may be used in implementing power management functions for device  10 . For example, storage and processing circuitry  12  may be used to adjust the gain of radio-frequency power amplifier circuitry on device  10  and may be used in adjusting input power levels provided to the input of radio-frequency power amplifier circuitry on device  10  from a transceiver circuit. Storage and processing circuitry  12  may also be used to adjust the power supply voltages that are used in powering the radio-frequency power amplifier circuitry. These adjustments may be made automatically in real time based on calibration data and operating algorithms (software). For example, code may be stored in storage and processing circuitry  12  that configures storage and processing circuitry  36  to implement a control scheme in which operating settings are adjusted to satisfy desired performance criteria such as desired transmit powers and adjacent channel leakage ratio values while minimizing power consumption. 
     Input-output devices  16  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. Examples of input-output devices  16  that may be used in device  10  include display screens such as touch screens (e.g., liquid crystal displays or organic light-emitting diode displays), buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers and other devices for creating sound, cameras, sensors, etc. A user can control the operation of device  10  by supplying commands through devices  16 . Devices  16  may also be used to convey visual or sonic information to the user of device  10 . Devices  16  may include connectors for forming data ports (e.g., for attaching external equipment such as computers, accessories, etc.). 
     Wireless communications devices  18  may include communications circuitry such as radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry (e.g., power amplifier circuitry that is controlled by control signals from storage and processing circuitry  14  to minimize power consumption while satisfying desired performance criteria), passive RF components, antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Device  10  can communicate with external devices such as accessories, computing equipment, and wireless networks over wired and wireless communications paths. 
     For example, accessories such as wired or wireless headsets may communicate with device  10 . Device  10  may also be connected to audio-video equipment (e.g., wireless speakers, a game controller, or other equipment that receives and plays audio and video content), or a peripheral such as a wireless printer or camera. 
     Device  10  may use a wired or wireless path to communicate with a personal computer or other computing equipment. The computing equipment may be, for example, a computer that has an associated wireless access point (router) or an internal or external wireless card that establishes a wireless connection with device  10 . The computer may be a server (e.g., an internet server), a local area network computer with or without internet access, a user&#39;s own personal computer, a peer device (e.g., another portable electronic device  10 ), or any other suitable computing equipment. 
     Device  10  can also communicate with wireless network equipment, such as cellular telephone base stations, cellular towers, wireless data networks, computers associated with wireless networks, etc. Such wireless networks may include network management equipment that monitors the wireless signal strength of the wireless handsets such as device  10  that are in communication with the network. To improve the overall performance of the network and to ensure that interference between handsets is minimized, the network management equipment may send power adjustment commands (sometimes referred to as transmit power control commands) to each handset. The transmit power control settings that are provided to the handsets direct handsets with weak signals to increase their transmit powers, so that their signals will be properly received by the network. At the same time, the transmit power control settings may instruct handsets whose signals are being received clearly at high power to reduce their transmit power control settings. This reduces interference between handsets and allows the network to maximize its use of available wireless bandwidth. 
     When devices such as device  10  receive transmit power control settings from the network or at other suitable times, each device  10  may make suitable transmission power adjustments. For example, a device may adjust the power level of signals transmitted from transceiver circuitry to radio-frequency power amplifiers on the device and may adjust the radio-frequency power amplifiers. Adjustments such as these may include gain mode settings adjustments and power supply voltage adjustments. 
     The output signals from the power amplifiers on devices  10  are wirelessly transmitted from device  10  to suitable receivers using antennas on devices  10 . The settings for wireless communications circuitry  18  may include gain mode adjustments that control the gain settings of power amplifiers. For example, a gain mode adjustment may control whether a power amplifier is operating in a high gain mode in which all power amplifier stages that are available are being used or a low gain mode in which one or more of the gain stages on the power amplifier have been shut down to conserve power. Power supply voltage adjustments may be used to help minimize power consumption at a given gain setting. In typical circuit architectures, a transceiver circuit may supply radio-frequency signals to the input of a power amplifier for transmission through an antenna. The power at which the transceiver circuit outputs these radio-frequency signals establishes an input power level (sometimes referred to herein as Pin) for the power amplifier. Input power adjustments (adjustments to Pin) can be made to adjust the power of radio-frequency signals transmitted by device  10 . 
     The antenna structures and wireless communications devices of device  10  may support communications over any suitable wireless communications bands. For example, wireless communications devices  18  may be used to cover communications frequency bands such as cellular telephone voice and data bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and the communications band data at 2170 MHz band (commonly referred to as a UMTS or Universal Mobile Telecommunications System 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, and the global positioning system (GPS) band at 1550 MHz. 
     Device  10  can cover these communications bands and other suitable communications bands with proper configuration of the antenna structures in wireless communications circuitry  18 . 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. 
     Illustrative wireless communications circuitry that may be used in circuitry  18  of  FIG. 1  in device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , wireless communications circuitry  44  may include one or more antennas such as antennas  62 . Data signals that are to be transmitted by device  10  may be provided to baseband module  52  (e.g., from storage and processing circuitry  12  of  FIG. 1 ). Baseband module  52  may be implemented using a single integrated circuit (e.g., a baseband processor integrated circuit) or using multiple circuits. Baseband processor  52  may receive signals to be transmitted over antenna  62  at input line  89  (e.g., from storage and processing circuitry  12 ). Baseband processor  52  may provide signals that are to be transmitted to transmitter circuitry within RF transceiver circuitry  54 . The transmitter circuitry may be coupled to power amplifier circuitry  56  via path  55 . Control path  88  may receive control signals from storage and processing circuitry  12  ( FIG. 1 ). These control signals may be used to control the power of the radio-frequency signals that the transmitter circuitry within transceiver circuitry  54  supplies to the input of power amplifiers  56  via path  55 . This transmitted radio-frequency signal power level is sometimes referred to herein as Pin, because it represents the input power to power amplifier circuitry  56 . 
     During data transmission, power amplifier circuitry  56  may boost the output power of transmitted signals to a sufficiently high level to ensure adequate signal transmission. Radio-frequency (RF) output stage circuitry  57  may contain radio-frequency switches and passive elements such as duplexers and diplexers. The switches in RF output stage circuitry  57  may, if desired, be used to switch circuitry  44  between a transmitting mode and a receiving mode. Duplexer and diplexer circuits and other passive components in RF output stage may be used to route input and output signals based on their frequency. 
     Matching circuitry  60  may include a network of passive components such as resistors, inductors, and capacitors and ensures that antenna structures  62  are impedance matched to the rest of the circuitry  44 . Wireless signals that are received by antenna structures  62  may be passed to receiver circuitry in transceiver circuitry  54  over a path such as path  64 . 
     Each power amplifier (e.g., each power amplifier in power amplifiers  56 ) may include one or more power amplifier stages such as stages  70 . 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  70 . Stages  70  may have control inputs such as inputs  72  that receive control signals. The control signals may be provided using a control signal path such as path  76 . In a typical scenario, storage and processing circuitry  12  ( FIG. 1 ) may provide control signals to stages  70  using a path such as path  76  and paths such as paths  72 . The control signals from storage and processing circuitry  12  may be used to selectively enable and disable stages  70 . 
     By enabling and disabling stages  70  selectively, the power amplifier may be placed into different gain modes. For example, the power amplifier may be placed into a high gain mode by enabling all three of power amplifier stages  70  or may be placed into a low gain mode by enabling two of the power amplifier stages. Other configurations may be used if desired. For example, a very low gain mode may be supported by turning on only one of three gain stages or arrangements with more than three gain mode settings may be provided by selectively enabling other combinations of gain stages (e.g., in power amplifiers with three or more than three gains stages). 
     Adjustable power supply circuitry such as adjustable power supply circuitry  78  may be powered by voltage source  83 . Voltage source  83  may be, for example, a battery such as battery  14  of  FIG. 1 . Source  83  may supply a positive battery voltage to adjustable power supply circuitry  78  at positive power supply terminal  82  and may supply a ground voltage to adjustable power supply circuitry  78  at ground power supply terminal  84 . Source  83  may be implemented using a lithium ion battery, a lithium polymer battery, or a battery  14  of any other suitable type. 
     Initially, the voltage supplied by battery source  83  may be high. As the battery becomes depleted, the voltage supplied by the battery will tend to drop. By using adjustable power supply circuitry  78 , the amount of voltage Vcc that is supplied to power amplifier circuitry  56  over power supply voltage path  86  may be maintained at a desired value. For example, power supply circuitry  78  may, under appropriate conditions, receive a raw battery voltage from source  83  that drops with time and may produce a relatively constant output power Vcc on output path  86 . This may help to avoid wasteful situations in which the circuitry of power amplifiers  56  is supplied with excessive voltages while the battery of source  83  is fresh. Such excessive voltages may lead to wasteful power consumption by circuitry  56 . 
     Adjustable power supply circuitry  78  may be controlled by control signals received over a path such as path  80 . The control signals may be provided to adjustable power supply circuitry  78  from storage and processing circuitry  12  ( FIG. 1 ) or any other suitable control circuitry. The control signals on path  80  may be used to adjust the magnitude of the positive power supply voltage Vcc that is provided to power amplifier circuitry  56  over path  86 . These power supply voltage adjustments may be made at the same time as gain mode adjustments are being made to the power amplifier circuitry  56  and at the same time that adjustments are being made to the power (Pin) on path  55 . By making power supply voltage adjustments, gain level adjustments to power amplifier circuitry  56 , and adjustments to the input power Pin at the input of power amplifier circuitry  56 , power consumption by power amplifier circuitry  56  can be minimized and battery life may be extended under a variety of operating conditions. 
     Consider, as an example, a situation in which device  10  has received a transmit power command from a wireless base station that specifies a desired level of radio-frequency power to be transmitted by device  10 . Storage and processing circuitry  12  can determine appropriate settings for wireless circuitry  44  that ensure that the desired power is transmitted through antenna  62 , while minimizing power consumption. If, for example, the desired amount of transmitted power is relatively low, power may be conserved by turning off one or more of stages  70  in power amplifier circuitry  56 . Power can also be conserved by reducing the power supply voltage Vcc that is supplied on path  86  when the maximum power supply voltage level is not required. Adjustments to Pin on path  55  may be made to ensure that performance requirements are met. 
     Adjustments such as these may be made by supplying control signals from storage and processing circuitry  12  to transceiver circuits  54  via path  88 , power amplifiers  56  via path  76 , and to adjustable power supply circuitry  78  via path  80 . In particular, control signals may be provided from storage and processing circuitry  12  to power amplifier circuitry  56  on path  76  that adjust the gain level of the power amplifier (e.g., by turning on and off certain gain stages  70  in power amplifier circuitry  56 ). Additional adjustments to the performance of the power amplifier circuitry  56  may be made by using path  86  to supply a desired adjustable power supply voltage Vcc to power amplifier circuitry  56  from adjustable power supply circuitry  78  in accordance with control signals supplied on path  80 . For example, if it is not necessary to operate the active amplifier stages in amplifier circuitry  56  at maximum gain, power can be conserved by lowering the power supply voltage Vcc to the active gain stages. At the same time, the magnitude of Pin on path  55  can be controlled. 
     During adjustments to transceiver circuitry  54 , power amplifier circuitry  56 , and power supply circuitry  78 , storage and processing circuitry  13  can take steps to satisfy desired operating constraints on power amplifier circuitry  56  such as minimum desired output power settings and minimum values of adjacent channel leakage ratio (the ratio of transmitted power to adjacent channel power). 
     Wireless communications circuitry  44  of  FIG. 2  may include circuitry for supporting any suitable types of wireless communications. For example, circuitry  44  may include circuits for supporting traditional cellular telephone and data communications (sometimes referred to as “2G” communications). An example of 2G cellular telephone systems are those based on the Global System for Mobile Communication (GSM) systems. Circuitry  44  may also include circuits for supporting newer communications formats (sometimes referred to as “3G” communications). These newer formats may support increased communications speeds and may be used for both data and voice traffic. Such formats may use wide band code-division multiple access (CDMA) technology. 
     Adjustable power supply circuitry  78  may be implemented using a DC/DC converter or any other suitable power conversion circuit. Circuitry  78  may receive a relatively higher voltage Vccbatt from battery  83  over power supply path  82  and may produce a corresponding regulated power supply voltage Vcc at a relatively lower voltage Vcc at output path  86 . In a typical arrangement, the battery voltage Vccbatt may range from about 4.3 volts to about 3.4 volts and output voltage Vcc may range from about 3.4 volts to 3.1 volts. The voltage Vcc may be adjusted based on control signals received over path  80 . Voltage Vcc may be adjusted continuously (e.g., to provide any desired output voltage in the range of 3.1 to 3.4 volts or other suitable range) or may be set to one of two or more discrete levels (e.g., 3.1 volts, 3.4 volts, etc.). 
     Power amplifier circuitry  56  may include multiple power amplifiers each of which handles a different communications band (e.g., bands at communications frequencies such as 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz). If desired, some or all of power amplifiers in circuitry  56  may handle multiple communications bands (e.g., adjacent bands). 
     Power amplifier circuitry  56  may receive control signals over path  76 . The control signals may be used to selectively turn on and off particular blocks of circuitry within each power amplifier. This type of adjustment may be used to place each power amplifier  56  in a desired gain mode. In a bimodal arrangement, each power amplifier may be placed in either a high gain mode or a low gain mode. If desired, other types of multimode arrangements may be supported (e.g., arrangements in which power amplifiers  56  can be adjusted to operate at three or more different gain settings.) 
     Components such as power amplifiers  56  do not always need to run at the maximum available battery voltage Vccbatt. Operating such components at battery voltages such as these can therefore waste power. To minimize the amount of wasted power, DC/DC converter circuitry  78  may be used to convert the unregulated and fluctuating voltage Vccbatt from its sometimes relatively high voltage levels to a more moderate power supply voltage level Vcc. The value of Vcc might be, for example, 3.1 volts or 3.4 volts (as an example). Because Vcc is significantly less than the maximum value of Vccbatt, power amplifiers  56  will not be overpowered and may therefore be powered efficiently. 
     If desired, the magnitude of power supply voltage Vcc may be adjusted in real time by storage and processing circuitry  12  to help minimize power consumption. A graph showing how an adjustable power supply circuit such as an adjustable dc-to-dc converter with a continuously variable output voltage Vcc may provide a radio-frequency power amplifier with suitable power supply voltages Vcc at various different power amplifier gain settings according to required values of transmitted radio-frequency power Pout is shown in  FIG. 3 . 
     As shown in  FIG. 3 , a power amplifier such as one of power amplifiers  56  may be characterized by two gain settings (as an example). In the  FIG. 3  example, various gain stages in power amplifier  56  may be selectively enabled so that power amplifier may be set to operate in one of two gain modes. In high gain mode, the power amplifier may be characterized by line “H.” In low gain mode, the power amplifier may be characterized by line “L.” 
     The curve of  FIG. 3  shows how the power supply voltage Vcc for the power amplifier may be reduced to minimize power consumption. The amount of power that may be saved depends, in general, on the amount of output power that is required at the output of power amplifier  56 . When required (e.g., in accordance with a wireless network TPC instruction or other requirement), the power amplifier may be operated in its maximum gain mode and at its highest operating voltage Vcc. For example, when an output power of 24 dBm is required (in the  FIG. 3  example), the power amplifier may be placed in its high gain mode and may be powered with a power supply voltage of V 1  (point 100 on line H). When a lower output power is required, such as 20 dBm, it is no longer necessary to operate the power amplifier at V 1 . Rather, the power supply voltage for the power amplifier may be reduced to a Vcc value of V 2  (point  102  on line H). This helps reduce power consumption. If an output power of 5 dBm is required, power consumption can be reduced further by placing the power amplifier in its low gain mode and reducing the power supply voltage to V 3  (point  104 ). 
     As the example of  FIG. 3  illustrates, both gain mode adjustments and power amplifier power supply voltage adjustments can be used in reducing power consumption for power amplifier  56 . If desired, the potential inefficiencies of DC/DC converter  78  under certain operating conditions may be taken into account when making adjustments of this type. The efficiency of DC/DC converter  78  and other power regulator circuitry may be affected by the operating voltage Vcc and operating current Icc that DC/DC converter  78  produces at its output. At high output voltages Vcc and high output currents Icc, adjustable power supply circuitry such as DC/DC converters may operate at peak efficiency. At lower Vcc and Icc levels, efficiency tends to drop. It may therefore be most efficient to reduce power supply voltage Vcc only in situations in which the power amplifier power savings that are obtained by reducing Vcc are not offset by increases in power consumption in DC/DC converter  78 . When Vcc is reduced, the values of power supply current and voltage that are used in powering power amplifier  56  tend to fall and overall power consumption will be reduced, so long as the reductions in power amplifier power consumption are not overwhelmed by power losses due to operating power supply circuitry  78  in an inefficient regime. 
     During operation of device  10 , storage and processing circuitry  12  may control the power supply voltage from power supply  78  in accordance with the graph of  FIG. 3 . Dashed lines  106  and  108  indicate how it may be desirable to incorporate hysteresis into the control algorithm. Hysteresis in the curve of  FIG. 3  may help transmitter circuitry in transceiver circuits  54  to satisfy phase discontinuity specifications. 
     The performance of wireless circuitry  18  in device  10  such as wireless circuitry  44  of  FIG. 2  varies as a function of operating frequency. As a result, circuitry  44  will exhibit more “headroom” at some operating frequencies than others. The additional margin that exists at particular operating frequencies represents a potential for additional power savings. The highest levels of amplifier performance typically require correspondingly large power supply voltages. As a result, if there is not much performance margin at a particular operating frequency, it can be difficult or impossible to reduce the power supply voltage for the power amplifier to conserve power. On the other hand, at frequencies at which there is sufficient operating margin, power consumption by the power amplifier circuitry can be minimized by reducing the power supply voltage as described in connection with  FIG. 3 . 
     An important performance characteristic in many wireless systems is so-called adjacent channel leakage ratio (ACLR). ACLR values are a measure of how well adjacent channels are isolated from each other. When adjacent channels are well isolated from each other, ACLR values will be low (e.g., less than −33 dBc or even lower). When signals from one channel spill over into an adjacent channel, ACLR will be high (e.g., more than −33 dBc). 
     A graph showing how ACLR may vary as a function of frequency in a given communications band is shown in  FIG. 4 . In the example of  FIG. 4 , device  10  is transmitting signals in a series of communications channels in a communications band that extends from lower frequency f 1  to higher frequency f 2 . This range of frequencies may be associated with any suitable communications band (e.g., the transmission frequencies associated with a 1900 MHz band, as an example). In  FIG. 4 , ACLR values are plotted as a function of device operating frequency f. Dashed line  110  indicates a typical carrier-imposed ACLR requirement of −33 dBc. When operating wireless devices in the network of a carrier that imposes a −33 dBc ACLR requirement, all portions of ACLR curve  114  must be less than −33 dBc (i.e., curve  114  must lie under dashed line  110  in the graph of  FIG. 4 ). Other carriers may impose more stringent or more lenient specifications. Moreover, a device manufacturer may decide to impose different standards. As an example, a device manufacturer may institute a self-imposed ACLR specification of −40 dBc, as illustrated by dashed line  112 . The device manufacturer may impose a more stringent ACLR specification than the carrier to ensure that users of devices such as device  10  will be provided with high quality signals and to allow for manufacturing variations in device  10 . 
     As the example of  FIG. 4  demonstrates, some frequencies, such as frequency fe are associated with particularly good adjacent channel leakage ratios, whereas other frequencies, such as frequency fh are associated with relatively poorer adjacent channel leakage ratios. As indicated by lines  116  and  118 , there is more operating margin at frequency fe than at frequency fh. Because of the additional overhead available at frequency fe, it is possible to reduce the power supply voltage Vcc for power amplifier circuitry  56  when device  10  is transmitting a radio-frequency signal in the channel at frequency fe. There is less overhead available at frequency fh, so little or no reduction to Vcc at fh may be made. By operating power amplifier circuitry  56  at a relatively high value of Vcc at frequency fh, the linearity of power amplifier circuitry  56  may be maximized, thereby helping device  10  produce its best possible ACLR value at fh. The reduced value of Vcc that is used at frequency fe may somewhat reduce the linearity of power supply circuitry  56  at frequency fe, causing power supply circuitry  56  to exhibit more adjacent channel leakage. This, in turn, will cause the ACLR value at frequency fe to increase, using up the operating margin  116 . Using margin  116  in this way allows the Vcc value at frequency fe to be reduced, thereby conserving power. 
     If desired, the output power from transceiver circuitry  54  (Pin) may be adjusted to compensate for frequency-dependent fluctuations in output power. Storage and processing circuitry  12  may make these adjustments by supplying control signals to control path  88  ( FIG. 2 ). 
     A graph showing how Pin may be adjusted as a function of frequency to ensure that a particular constant output voltage Pout-desired is produced at the output of power amplifiers  56  (and antennas  62 ) is shown in  FIG. 5 . As the graph of  FIG. 5  demonstrates, a given communications band (ranging from frequency f 1  to frequency f 2 ) may have some frequencies such as frequency fa in which power amplifier circuitry  56  is characterized by a relatively low gain Ga, so that a relatively large Pin value is needed at the output of transceiver circuits  54 . At other frequencies in the same band, such as frequency fb, power amplifier circuitry  56  is characterized by a relatively higher gain Gb, so that a relatively small Pin value can be supplied at the output of transceiver circuits  54 . In both situations, the combination of Pin and amplifier gain result in the same output power level (Pout-desired). 
     The reductions in operating voltage Vcc that can be made selectively as a function of frequency to take advantage of excess ACLR overhead may be stored in a given device  10  in the form of frequency-dependent power supply voltage offset data. A typical power supply voltage offset curve is shown in  FIG. 6 . As shown in the  FIG. 6  example, there may be particular frequencies at which it is possible to reduce the power supply voltage Vcc considerably and there may be particular frequencies at which little or no reduction to Vcc for power amplifier circuitry  56  is possible while still meeting required performance criteria such as required ACLR values. Because the magnitude of the Vcc reductions that are possible while meeting ACLR specifications depend upon frequency, the Vcc reductions form an offset curve or table. This offset data may be stored in memory in device  10  (e.g., storage and processing circuitry  12 ), so that device  10  can make appropriate Vcc adjustments during normal operation. 
     Characterizing measurements may be made to device  10  in any suitable environment. With one suitable arrangement, some characterizing measurements are made during laboratory testing. These characterizing measurements may then be stored in all devices  10  that are manufactured. Additional characterizing measurements may, if desired, be made during manufacturing (e.g., as part of a testing and calibration process in a factory). Other characterizing and calibration operations may also be performed if desired. 
     Radio-frequency calibration may be performed using any suitable test and measurement equipment. Illustrative equipment that may be used is shown in  FIG. 7 . As shown in  FIG. 7 , electronic device  10  may be characterized using systems such as system  120  that contain test equipment  122 . Equipment  122  may include radio-frequency measurement equipment such as spectrum analyzer equipment, power meter equipment, etc. Equipment  122  may be connected to an antenna connector in device  10  using a radio-frequency transmission line path such as path  124 . The radio-frequency connector in device  10  may, for example, be located between antennas  62  and the output of power amplifier circuitry  56 . Transmission line  124  may be, for example, a coaxial cable. Paths such as path  126  may be formed between device  10  and external equipment. Following testing, test equipment  122  or other suitable equipment may use paths such as path  126  to load calibration information into device  10 . Calibration data may be provided in the form of register settings, firmware, a portion of an operating system, device drivers, or any other suitable data. If desired, some of the calibration settings may be provided using one technique (e.g., as part of the initial software loaded onto device  10 ), whereas additional calibration settings may be provided to device  10  using another technique (e.g., by loading corrective data following test measurements that are made as part of a manufacturing process). 
     A flow chart of illustrative steps that may be made to gather power supply voltage offset data such as the data represented by the voltage offset curve of  FIG. 6  are shown in  FIG. 8 . Operations of the type shown in  FIG. 8  may be performed at any suitable time. For example, the characterizing measurements of the flow chart in  FIG. 8  may be made as part of an initial calibration operation when one or more representative devices  10  are first characterized in a laboratory. Measurements of the type shown in  FIG. 8  may also be performed in a manufacturing environment, if desired. 
     At step  128 , in a measurement system such as system  120  of  FIG. 7 , the output power Pout from power amplifier circuitry  56  may be measured at a given frequency f. The output power Pout may be measured using test equipment  122 , which is coupled to device  10  using transmission line  124 . The measurement at step  128  may be made at a particular power supply voltage Vcc on path  86  and may be made with particular gain stages  70  in power amplifier circuitry  56  enabled. A variety of different Pin values may be used in making the power output measurement of step  128  so as to identify a Pin value at which Pout is equal to Pout-desired ( FIG. 5 ). Data on the current settings of wireless circuitry  44  are then retained. For example, equipment  122  can populate a database table or other data structure with information related to the setting of transceiver circuitry  54  (i.e., the Pin value produced on path  55 ), the setting of power amplifiers  56  (i.e., which stages are enabled), the power supply voltage Vcc that is produced by supply circuitry  78 , and the resulting Pout value measured by equipment  122  over path  124 . 
     At step  130 , at the same frequency f, equipment  122  may be used to make performance characterizing measurements such as measurements of the device&#39;s adjacent channel leakage ratio. Performance measurements (e.g., the measured ACLR value for frequency f, power supply voltage Vcc, and input power Pin) may be stored as part of the measurements results data gathered by test equipment  122 . 
     At step  132 , a new frequency in the current band may be selected at which to perform measurements. As shown by line  134 , processing may then loop back to step  128 . After all frequencies f in the current communications band have been measured at a given value of power amplifier power supply voltage Vcc, a new Vcc value may be selected (step  136 ). Processing may then again loop back to step  128 , as indicated by line  138 . 
     The operations of loops  134  and  138  allow test equipment  122  to determine the minimum power supply voltage Vcc that may be used to power the power amplifier circuitry  56  at each frequency f while producing a required output power (Pout-desired). If, as an example, the value of Pout-desired is 24 dBm, the operations of loops  134  and  138  allow identification of those Pin values and Vcc values that will produce a Pout value of  24  dBm at each frequency f. If, at a given voltage Vcc, it is not possible to produce Pout-desired, even at the largest available Pin settings, test equipment  122  may store data indicating the minimum Vcc value that is required to successfully produce Pout-desired. 
     After all voltages Vcc of interest have been covered for the current communications band and corresponding data has been gathered and stored by equipment  122 , processing may proceed to step  140 . During step  140 , test equipment  122  may select an additional communications band of interest. For example, if the 850 MHz band has been covered, processing may proceed to the 900 MHz band. If the 850 MHz and 900 MHz bands have been covered, processing may proceed to the 1800 MHz band, etc. After selecting the next band of interest, processing may loop back to step  128 , as indicated by line  142 . 
     After all communications bands for device  10  have been covered, a power supply voltage offset characteristic such as the data of  FIG. 6  may be computed (step  144 ). During step  144 , test equipment  122  or other suitable computing equipment may analyze the data that has been gathered by test equipment  122  (i.e., the data that has been gathered and stored during steps  128  and  130 ). This data includes information identifying the minimum possible power amplifier supply voltage level (Vcc) that may be used at each frequency to successfully produce Pout-desired, while satisfying performance criteria such as the required ACLR values. 
     The analysis of step  144  may determine that at a particular frequency (e.g., frequency fe of  FIG. 4 ), there is sufficient ACLR operating margin to reduce Vcc substantially. The minimum Vcc value that may be used to produce Pout-desired at this frequency may be less than a nominal operating voltage (e.g., 3.4 volts). Accordingly, the difference between the nominal operating voltage for powering power amplifier circuitry  56  and the minimum Vcc value (e.g., −0.5 volts) will represent the offset voltage value at frequency fe (in this example). At other frequencies, such as at frequency fh of  FIG. 4 , the analysis of step  144  may determine that Vcc cannot be reduced below its nominal operating voltage (e.g., 3.4 volts) while still satisfying Pout-desired and ACLR requirements. In this situation, the offset voltage will be zero (e.g., the offset voltage at frequency fh will be 0 volts). Other frequencies will have intermediate Vcc offset values. 
     The Vcc offset data that is produced at step  144  represents information on the magnitude of the power supply voltage reductions that may be made for each frequency of operation in device  10  to minimize power consumption, while still satisfying minimum output power and ACLR performance constraints. This information may be supplied to devices  10  using any suitable arrangement. For example, voltage offset settings may be stored in devices  10  when devices  10  are initially loaded with software during manufacturing, as part of a software update, using hardware settings, or using any other suitable arrangement. If desired, the same voltage offset data may be stored in each of the devices  10  that is manufactured. In this type of scenario, the voltage offset data represents global power supply voltage reduction settings for power supply  78 . Power supply voltage versus required output power characteristics such as the data of  FIG. 3  may also be stored in each device for use in controlling power supply  78 . 
     Global settings such as these are not specific to a particular device  10 . During manufacturing, it may be desirable to calibrate each device  10  individually. The same test equipment may be used in performing global characterizing measurements and in performing individual characterizing measurements or separate test systems may be used. For example, global characterizing measurements that are used in ascertaining suitable voltage versus output power curves of the type shown in  FIG. 3  and that are used in producing power supply voltage versus frequency data of the type described in connection with the voltage offset curve of  FIG. 6  may be produced with one characterization system (e.g., in a design environment) and additional calibration measurements may be made during manufacturing using another characterization system (e.g., in a manufacturing environment). The same system may also be used for all characterizing measurements if desired. 
     Illustrative steps involved in performing global and individual device calibration operations are shown in  FIG. 9 . 
     At step  146 , test equipment may be used to determine global gain settings and power supply voltage settings that may be used to allow devices  10  to reduce power consumption at various required output power levels. For example, at high output power levels such as when operating a device at a 24 dBm output power (point  100  of  FIG. 3 ), a voltage of V 1  may be used in powering radio-frequency power amplifier circuitry and power amplifier circuitry  56  may be operated in a “high” gain mode in which all of its gain stages  70  are enabled. At lower output power levels, power supply voltage Vcc and/or the number of gain stages that are enabled in power amplifier circuitry  56  may be scaled back, as described in connection with  FIG. 3 . 
     The power supply voltage versus output power characteristic of  FIG. 3  is the same for all operating frequencies. At step  148 , the frequency dependence of wireless circuitry  44  may be characterized by performing measurements and calculations of the types described in connection with  FIG. 8 . In particular, during step  148 , additional (offset) changes that may be made to the power supply voltage Vcc may be ascertained for each desired operating frequency. 
     The global characterizing data obtained during steps  146  and  148  may be loaded into devices  10  during manufacturing or at other suitable times (step  150 ). 
     At step  152 , individual characterizing measurements may be made. As these characterizing measurements are being made, each device  10  may use its storage and processing circuitry  12  to implement a control algorithm based on the Vcc and gain versus output power characteristic of  FIG. 3  and the Vcc versus frequency characteristics of  FIG. 6  (with appropriate scaling for different output powers). The calibration measurements of step  152  may be used to produce a family of curves, each of which corresponds to a different output power value. For example, Pout-desired may be decreased in 1 dB steps from 24 dBm to −50 dBm. For each respective Pout-desired setting, the operating frequency f may be swept while the required Pin value for producing the current Pout-desired value may be measured. The characterizing operations of step  152  may therefore serve to produce a family of Pin versus frequency curves for a variety of discrete Pout settings. If desired, characterizing operations may be performed in which calibration data is gathered and represented in different formats (e.g., semi-continuously, using steps of different sizes, performing sweeps of different variables, etc.). 
     The device-specific calibration information that is gathered during step  152  may be stored in the corresponding device  10  at step  154 . For example, a path such as data path  126  of  FIG. 7  or other suitable communications path may be used to store information in storage in device  10  on which Pin values should be produced by transceiver circuitry  54  for each frequency. During operation, this information may be used by device  10  in conjunction with previously-stored information in device  10  on the particular Vcc setting and gain setting from the previously-stored calibration results to select appropriate operating parameters for circuitry  44 . 
     After performing the device-specific calibration operations of step  154 , device  10  may be shipped to a user and used to communicate. For example, a user may use device  10  to make cellular telephone calls and to send and receive cellular telephone non-voice data (step  156 ). During operation, device  10  can use the calibration settings that were obtained at steps  146 ,  148 , and  152 . In particular, device  10  can select which power supply voltage Vcc to use and which gain stages in amplifier circuitry  56  are to be turned on by selecting an appropriate operating point on curves of the type shown in  FIG. 3  based on required output power. Power supply voltage versus frequency characteristics may also be used in controlling the operation of wireless circuitry  44 , as described in connection with  FIG. 6 . 
     If desired, the offset-voltage versus frequency characteristics used by device  10  may be scaled back at lower output powers to avoid over-adjusting Vcc as a function of frequency at lower Pout settings. For example, the offset voltage versus frequency characteristic of device  10  may be fully used at high powers (e.g., at output powers of 24 dBm), but may be phased out gradually at lower powers. This phase out process may be implemented progressively, so that when a particular low output power value is reached (e.g., 16 dBm), the voltage offset versus frequency characteristic is completely phased out and has no further impact (e.g., there is no frequency component to the Vcc adjustments that are made at output powers below 16 dBm). 
     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: 20081030
Publication Date: 20121211
Grant Date: 20121211
Priority Date: 20081030
Inventors: SORENSEN ROBERT
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B1/1607", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W88/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W52/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B1/1607", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 41413090