PATENT DOCUMENT

Publication Number: US-9071302-B2
Application Number: US-201113226367-A
Country: US
Kind Code: B2

Title: Radio-frequency power amplifier circuitry with power supply voltage optimization capabilities

Abstract:
Electronic devices with wireless communications capabilities are provided. The electronic device may include storage and processing circuitry, power amplifier circuitry, power supply circuitry, etc. The storage and processing circuitry may direct the power amplifier circuitry to operate using a desired power mode, in allocated resource blocks within a particular frequency channel, and at a given output power level. The power supply circuitry may bias the power amplifier circuitry with a power supply voltage. The electronic device may be subject to in-band emissions requirements and adjacent channel leakage requirements that restrict the power levels produced by the device on frequencies that are not allocated to the device. The electronic device may optimize the power amplifier supply voltage based on allocated resource blocks by minimizing the supply voltage to reduce power consumption while ensuring that emissions requirements are satisfied.

Claims:
What is claimed is: 
     
       1. Circuitry on a portable electronic device, comprising:
 radio-frequency transceiver circuitry configured to transmit radio-frequency signals in resource blocks within a frequency band containing multiple resource blocks; 
 a radio-frequency power amplifier that amplifies radio-frequency signals that are wirelessly transmitted from the radio-frequency transceiver circuitry in the resource blocks; 
 adjustable power supply circuitry that supplies an adjustable power supply voltage to the radio-frequency power amplifier; and 
 storage and processing circuitry configured to adjust the adjustable power supply voltage supplied by the adjustable power supply circuitry to the radio-frequency power amplifier based at least partly on how many of the resource blocks are being used for wirelessly transmitting the radio-frequency signals, wherein the storage and processing circuitry increases the adjustable power supply voltage for resource blocks located at edges of the frequency band and decreases the adjustable power supply voltage for resource blocks located near a center of the frequency band. 
 
     
     
       2. The circuitry defined in  claim 1  wherein the storage and processing circuitry is configured to store calibration data specifying adjustments to make to the adjustable power supply voltage using the adjustable power supply circuitry based at least partly on how many of the resource blocks are being used for wirelessly transmitting the radio-frequency signals. 
     
     
       3. The circuitry defined in  claim 1  wherein the amplified radio-frequency signals are transmitted in the resource blocks at an output power level and wherein the storage and processing circuitry is configured to adjust the adjustable power supply voltage supplied by the adjustable power supply circuitry to the radio-frequency power amplifier based at least partly on the output power level. 
     
     
       4. The circuitry defined in  claim 1  wherein the frequency band comprises Long Term Evolution (LTE) band 13 and wherein the storage and processing circuitry is configured to adjust the adjustable power supply voltage supplied by the adjustable power supply circuitry to the radio-frequency power amplifier based at least partly on how many resource blocks within LTE band 13 are being used for wireless transmitting the radio-frequency signals. 
     
     
       5. The circuitry defined in  claim 1  wherein the radio-frequency transceiver circuitry is configured to communicate with a base station that allocates to the portable electronic device a selected number of the resource blocks within the frequency band and wherein the storage and processing circuitry is configured to adjust the adjustable power supply voltage supplied by the adjustable power supply circuitry to the radio-frequency power amplifier based at least partly on the selected number of resource blocks. 
     
     
       6. The circuitry defined in  claim 1  wherein the frequency band is subject to adjacent band emissions requirements associated with limits on interference between the frequency band and adjacent frequency bands, wherein the resource blocks are subject to in-band emissions requirements associated with limits on interference between resource blocks within the frequency band, and wherein the storage and processing circuitry is configured to store calibration data specifying adjustments that are made to the adjustable power supply voltage to conserve power while satisfying the adjacent band emissions requirements and the in-band emissions requirements. 
     
     
       7. The circuitry defined in  claim 6  wherein the calibration data that is stored specifies adjustments that are made to the adjustable power supply voltage to minimize the adjustable power supply voltage to conserve power while ensuring that the adjustable power supply voltage has a value sufficient to ensure that the amplified radio-frequency signals satisfy the adjacent band emissions requirements and the in-band emissions requirements. 
     
     
       8. The circuitry defined in  claim 1  wherein the storage and processing circuitry is configured to increase the adjustable power supply voltage in response to identifying an increase in how many of the resource blocks are being used for wirelessly transmitting the radio-frequency signals. 
     
     
       9. The circuitry defined in  claim 1  wherein the storage and processing circuitry is configured to decrease the adjustable power supply voltage in response to identifying a decrease in how many of the resource blocks are being used for wirelessly transmitting the radio-frequency signals. 
     
     
       10. The circuitry defined in  claim 1  wherein the storage and processing circuitry is configured to increase the adjustable power supply voltage in response to identifying that the resource blocks being used for wireless transmitting the radio-frequency signals are located at an edge of the frequency band. 
     
     
       11. The circuitry defined in  claim 1  further comprising:
 a duplexer that receives the amplified radio-frequency signals from the radio-frequency power amplifier, wherein the storage and processing circuitry is configured to adjust the adjustable power supply voltage based at least partly on insertion loss from the duplexer. 
 
     
     
       12. A method of operating a wireless device that is allocated a number of Long-Term-Evolution (LTE) resource blocks within a LTE frequency band having multiple LTE resource blocks, the method comprising:
 with radio-frequency transceiver circuitry, transmitting radio-frequency signals in the LTE resource blocks within the LTE frequency band; 
 with a radio-frequency power amplifier, amplifying radio-frequency signals in at least some of the LTE resource blocks; 
 with adjustable power supply circuitry, supplying an adjustable power supply voltage to the radio-frequency power amplifier; 
 with storage and processing circuitry, adjusting the adjustable power supply voltage supplied by the adjustable power supply circuitry to the radio-frequency power amplifier based at least partly on how many of the LTE resource blocks in the LTE frequency band are allocated to the wireless device; and 
 with the storage and processing circuitry, controlling the adjustable power supply circuitry to increase the adjustable power supply voltage when one or more of the allocated LTE resource blocks are located at edges of the LTE frequency band and to decrease the adjustable power supply voltage when the allocated LTE resource blocks are located near a center of the LTE frequency band. 
 
     
     
       13. The method defined in  claim 12  wherein adjusting the adjustable power supply voltage comprises increasing the adjustable power supply voltage in response to identifying an increase in how many of the resource blocks are being used for wirelessly transmitting the radio-frequency signals. 
     
     
       14. The method defined in  claim 12 , wherein the frequency band is subject to adjacent band emissions requirements associated with limits on interference between the frequency band and adjacent frequency bands, wherein the resource blocks are subject to in-band emissions requirements associated with limits on interference between resource blocks within the frequency band, and wherein adjusting the adjustable power supply voltage comprises:
 adjusting the adjustable power supply voltage to minimize power consumption while satisfying the adjacent band emissions requirements and the in-band emissions requirements. 
 
     
     
       15. The method defined in  claim 12 , wherein the LTE resource blocks in the LTE frequency band that are allocated to the wireless device are allocated to the wireless device by a wireless base station. 
     
     
       16. Wireless communications circuitry configured to communicate with a base station in resource blocks within a frequency band containing multiple resource blocks, wherein the frequency band is subject to adjacent band emissions requirements associated with limits on interference between the frequency band and adjacent frequency bands, and wherein the resource blocks are subject to in-band emissions requirements associated with limits on interference between resource blocks within the frequency band and wherein the frequency band has a center frequency and edge frequencies, the wireless communications circuitry comprising:
 an antenna; 
 a radio-frequency power amplifier that amplifies radio-frequency signals that are transmitted from the electronic device to the base station using a plurality of resource blocks; 
 adjustable power supply circuitry that supplies an adjustable power supply voltage to the power amplifier circuitry; and 
 storage and processing circuitry configured to adjust the adjustable power supply voltage supplied by the adjustable power supply circuitry to the radio-frequency power amplifier based on where the plurality of resource blocks are located within the frequency band to minimize power consumption while satisfying the adjacent band emissions requirements and the in-band emissions requirements by:
 increasing the adjustable power supply voltage when the plurality of resource blocks are near the edge frequencies of the frequency band; and 
 reducing the adjustable power supply voltage when the plurality of resource blocks are near the center frequency of the frequency band. 
 
 
     
     
       17. The wireless communications circuitry defined in  claim 16  wherein the storage and processing circuitry is configured to adjust the adjustable power supply voltage based at least partly on how many of the resource blocks are being used to communicate with the base station. 
     
     
       18. The wireless communications circuitry defined in  claim 16  wherein the storage and processing circuitry is configured to increase the adjustable power supply voltage in response to identifying an increase in how many resource blocks are being used to communicate with the base station.

Description:
BACKGROUND 
     This invention relates generally to wireless communications circuitry, and more particularly, to ways in which to optimize wireless communications performance by making power amplifier power supply voltage adjustments. 
     Integrated circuits often have wireless communications circuitry that includes radio-frequency power amplifiers. Radio-frequency power amplifiers are used to amplify radio-frequency signals for wireless transmission in a desired channel. 
     Radio-frequency power amplifiers typically exhibit reduced power consumption at lower supply voltages. Lowering the supply voltage that biases the power amplifiers directly decreases the supply current that flows through the radio-frequency power amplifiers, thereby saving power. Lowering the supply voltage, however, degrades power amplifier linearity. Degrading power amplifier linearity in this way may undesirably increase radio-frequency emissions on frequencies that are outside the transmission frequencies. 
     It would therefore be desirable to be able to provide improved power supply biasing capabilities to wireless devices. 
     SUMMARY 
     Electronic devices may include wireless communications circuitry. The wireless communications circuitry may include storage and processing circuitry, radio-frequency input-output circuits, radio-frequency power amplifier circuitry, adjustable power supply circuitry, and other wireless circuits. 
     The radio-frequency input-output circuits may feed signals to the power amplifier circuitry. The power amplifier circuitry may amplify the signals prior to wireless transmission. The power amplifier circuitry may include multiple power amplifier stages. The storage and processing circuitry may control these stages to place the power amplifier circuitry in a desired power mode. For example, the power amplifier may be placed into a high power mode by enabling all of the power amplifier stages or may be placed into a low power mode by enabling one of the power amplifier stages. The power mode may also be adjusted by adjusting a bias voltage or bias current to each stage of the power amplifier. 
     The storage and processing circuitry may bias the power amplifier circuitry at a desired positive power supply voltage. The power supply voltage may be supplied to each of the power amplifier stages. Adjustments to the power supply may be made to ensure that emissions requirements are satisfied while minimizing power consumption. 
     A wireless electronic device may communicate with a base station via radio-frequency signals in a frequency channel (e.g., a range of frequencies). The base station may allocate resource blocks within the frequency channel to the wireless electronic device. Each resource block may correspond to a range of frequencies within the frequency channel. To communicate with the base station, the wireless electronic device may transmit radio-frequency signals in the allocated resource blocks. 
     The wireless electronic device may be subject to emissions requirements such as adjacent channel leakage ratio (ACLR) requirements and in-band emissions requirements. The adjacent channel leakage ratio requirements may limit the amount of power generated by the wireless device on frequencies outside of the transmission frequency channel. The in-band emissions requirements may limit the amount of power generated by the wireless device in resource blocks within the frequency channel that are not allocated to the device. 
     The amount of undesired emissions (e.g., radio-frequency signals generated outside of allocated resource blocks) produced by the wireless electronic device may be controlled by adjusting the supply voltage provided to the power amplifier. To optimize the power amplifier supply voltage, the wireless device may minimize the supply voltage to reduce power consumption while ensuring that emissions requirements are satisfied. 
     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 that may communicate with a base station in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram of an illustrative electronic device with wireless communications circuitry in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram showing an illustrative frequency band that is partitioned into resource blocks in accordance with an embodiment of the present invention. 
         FIG. 4  is a graph illustrating how power amplifier supply voltage may be adjusted to satisfy emissions requirements in accordance with an embodiment of the present invention. 
         FIG. 5  is a graph illustrating how power amplifier supply voltage may be adjusted based on allocated resource blocks in accordance with an embodiment of the present invention. 
         FIG. 6  is a graph illustrating how power amplifier supply voltage may be adjusted based on the location of allocated resource blocks in accordance with an embodiment of the present invention. 
         FIG. 7  is a graph illustrating how duplexer insertion loss may vary with frequency in accordance with an embodiment of the present invention. 
         FIG. 8  is an illustrative table that may store power supply settings for various output powers and resource block allocations in accordance with an embodiment of the present invention. 
         FIG. 9  is a flow chart of illustrative steps involved in determining optimum supply voltage settings for biasing radio-frequency power amplifier circuitry in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     This relates generally to wireless communications, and more particularly, to biasing wireless communications circuitry at optimum supply voltage levels in wireless electronic devices. 
     The wireless electronic devices that are biased in this way 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 a scenario in which a wireless electronic device  10  may communicate with a base station  6  over a wireless communications link  8 . Wireless communications link  8  may be established by radio-frequency transmissions between base station  6  and wireless electronic device  10 . Wireless communications link  8  may serve as a data connection over which wireless electronic device  10  may send and receive data from base station  6 . The radio-frequency transmissions may be sent using cellular standards such as the 3GPP Long Term Evolution (LTE) protocol. 
       FIG. 2  shows an illustrative electronic device that includes wireless communications circuitry. As shown in  FIG. 2 , device  10  may include one or more antennas such as antennas (antenna structures)  34  and may include radio-frequency (RF) input-output circuits  12 . During signal transmission operations, circuitry  12  may supply radio-frequency signals that are transmitted by antennas  34 . During signal reception operations, circuitry  12  may accept radio-frequency signals that have been received by antennas  34 . 
     The antenna structures and wireless communications circuitry of device  10  may support communications over any suitable wireless communications bands. For example, the wireless communications circuitry 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 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, and the global positioning system (GPS) band at 1575 MHz. The wireless communications bands used by device  10  may include the so-called LTE (Long Term Evolution) bands. The LTE bands are numbered (e.g., 1, 2, 3, etc.) and are sometimes referred to as E-UTRA operating bands. 
     Device  10  can cover these communications bands and other suitable communications bands with proper configuration of the antenna structures in the wireless communications circuitry. 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 services, 3 G communications protocols, 4 G communications protocols such as LTE, etc. 
     Data signals that are to be transmitted by device  10  may be provided to baseband module  18 . Baseband module  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 over antenna  34  over path  13  from storage and processing circuitry  16 . Baseband processor  18  may provide signals that are to be transmitted to transmitter circuitry within RF transceiver circuitry  14 . The transmitter circuitry may be coupled to radio-frequency power amplifier circuitry  20  via transmit 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 circuitry 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 circuits  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. 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 ensures that antenna structures  34  are impedance matched to the rest of the wireless circuitry. Wireless signals that are received by antenna structures  34  may be passed to receiver circuitry in transceiver circuitry  14  over a receive 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 by enabling all three of power amplifier stages  22  or may be placed into a low power 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). As another example, the power amplifier may be placed into a high power mode by increasing bias currents 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  to power amplifier circuitry  20  that adjust bias currents provided to amplifiers  22 ). By adjusting the power mode of the amplifier, the output power capabilities of power amplifier circuitry  20  may be adjusted to maximize efficiency (e.g., for a given desired 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 circuits  14 , etc.). 
     Storage and processing circuitry  16  may maintain a table of 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 . Based on the known operating conditions of circuitry  44  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 output  30  of duplex filter  28 ), the desired transmit frequency, resource block allocation (e.g., how many resource blocks are allocated to the device and/or the locations of the resource blocks within a frequency channel), and based on the values of the 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 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  and terminal  42  over path  42 . These power supply voltage adjustments may be made during testing and during normal operation of device  10 . 
       FIG. 3  shows how a channel (band)  54  may be partitioned in frequency into resource blocks  52 . Channel  54  may be a frequency range in which device  10  may communicate with base station  6 . For example, channel  54  may be LTE band 9, band 13, etc. Channel  54  may be bounded by a low frequency f L  and a high frequency f H . For example, LTE band 9 may have a low frequency f L  of approximately 1750 MHz and a high frequency f H  of approximately 1785 MHz. 
     The available bandwidth of channel  54  may be partitioned into any desired number of resource blocks  52  (e.g., resource blocks  52  may be frequency ranges within the frequency channel). For example, an LTE channel may be partitioned into 50 resource blocks  52  that are allocated to wireless electronic devices by a base station. Wireless electronic device  10  may communicate with a base station by transmitting radio-frequency signals on the frequencies associated with resource blocks that are allocated to the wireless electronic device. The data rate at which device  10  may communicate with the base station may correspond to the number of resource blocks that have been allocated to device  10  (e.g., the bandwidth allocated to device  10 ). 
     Wireless device  10  may be expected to transmit radio-frequency signals only in resource blocks that have been allocated to the device. However, power amplifier circuitry  20  may undesirably produce radio-frequency signals on frequencies that have not been allocated to power amplifier circuitry  20 . For example, the output signal of power amplifier circuitry  20  may include intermodulation components at frequencies outside of the transmission frequency range (e.g., outside of the allocated resource blocks). The wireless emissions produced at frequencies outside of the transmission frequency range may sometimes be referred to as spectral regrowth. The amount of wireless emissions produced at frequencies outside of the transmission frequency range may depend on the linearity of power amplifier circuitry  20  (e.g., how linearly power amplifier circuitry  20  amplifies input signals). 
     The linearity of power amplifier circuitry  20  may be dependent on the supply voltage provided to the power amplifier. For example, if the supply voltage is too low, then the power amplifier may have insufficient headroom to linearly amplify input signals. In this scenario, input signals that are too large may result in amplified output voltages that are limited by the power supply voltage (sometimes referred to as gain compression). The gain of power amplifier circuitry  20  may therefore be dependent on the amplitude of the input voltage. In other words, the output signal of the amplifier may no longer linearly correspond to the input signal. Non-linear amplification by power amplifier circuitry  20  may produce spectral content on frequencies that are not present in the input signal. 
     By adjusting supply voltage Vcc provided to power amplifier circuitry  20  over path  42  (e.g., as shown in  FIG. 2 ), wireless electronic device  10  may adjust the linearity of the power amplifier, thereby controlling the power levels of radio-frequency signals produced at frequencies that are not allocated to device  10 .  FIG. 4  shows an illustrative scenario in which a wireless device  10  that is allocated resource block  52 A within channel  54  may adjust the supply voltage supplied to power amplifier circuitry  20  to reduce undesirable spectral content such as spectral regrowth (e.g., to reduce radio-frequency signals produced on frequencies outside of resource block  52 A). In  FIG. 4 , an illustrative output power spectrum (e.g., output power levels at various frequencies) of device  10  at various supply voltages is shown. 
     In the example of  FIG. 4 , wireless device  10  may transmit radio-frequency signals in allocated block  52 B at an output power Pout. Pout may be a minimum power level required to communicate with a base station (e.g., the base station may be unable to properly receive radio-frequency transmissions from device  10  that have a power level lower than Pout). Curves  62 ,  64 , and  66  may represent output power levels of power amplifier circuitry  20  for various frequencies and at respective supply voltages. Curve  62  may represent the output power of power amplifier circuitry  20  at a relatively low supply voltage (e.g., approximately 0.5 V). Curve  64  may represent the output power of power amplifier circuitry  20  at a moderate supply voltage (e.g., approximately 2.0 V). Curve  66  may represent the output power of power amplifier circuitry  20  at a relatively large supply voltage (e.g., approximately 3.0 V). These examples are merely illustrative, curves  62 - 66  may represent any desirable power amplifier supply voltages in which the supply voltage of curve  66  is greater than the supply voltage of curve  64  and in which the supply voltage of curve  64  is greater than the supply voltage of curve  62 . 
     Output power levels of device  10  in each resource block may depend on the separation in the frequency domain between that resource block and the frequencies of transmission (e.g., the frequencies in allocated resource block  52 A). Output power levels for frequencies that are outside of allocated resource block  52 A may decrease with increased separation in frequency from the transmission frequency range (e.g., from allocated resource block  52 A). For example, the output power levels in resource blocks  52  for curve  62  may be less than the output power levels in resource blocks  52 B (e.g., because resource blocks  52  may be farther from the transmission frequency range than resource blocks  52 B). 
     Wireless device  10  may be subject to requirements that limit the maximum power levels of radio-frequency signals that are produced in resource blocks of a given frequency channel that are not allocated to device  10  (sometimes referred to as in-band emissions requirements). Wireless device  10  may be required to maintain in-band emissions below P IN-BAND  (e.g., output power produced by device  10  may be required to remain below P IN-BAND  for frequencies within channel  54  that have not been allocated to device  10 ). If device  10  were to produce radio-frequency signals in adjacent resource blocks  52 B with power levels greater than P IN-BAND  (as shown by curve  62 ), the operation of another device operating in resource blocks  52 B may be disrupted (as an example). The in-band emissions requirements may be determined by the ability of base station  6  to distinguish between transmission signals and interfering signals. 
     Device  10  may be required to maintain out-of-channel emissions below P ACLR  (e.g., output power produced by device  10  may be required to remain below P ACLR  for frequencies outside of channel  54 ). The adjacent channel leakage requirements may be determined by the ability of radio-frequency receivers in other base stations or in other electronic devices to distinguish between transmission signals and interfering signals. 
     The in-band emission requirements may be less restrictive than the adjacent channel leakage requirements. For example, P IN-BAND  may be 3 dB below P out  while P ACLR  may be 33 dB below P out . The in-band emission requirements may be less restrictive because base station  6  may be able to consume additional power to distinguish between transmission signals and interfering signals, while base stations of different standards may have unknown reception capabilities (as examples). 
     As shown by curve  62 , device  10  that operates at a relatively low supply voltage such as 0.5 V may generate undesired radio-frequency signals in adjacent resource blocks  52  and  52 B that are higher than P IN-BAND  (e.g., due to non-linear amplification of the radio-frequency signals in allocated resource block  52 A). To prevent the undesired radio-frequency signals from interfering with radio-frequency communications in adjacent resource blocks  52  and  52 B, device  10  may increase the power supply voltage provided to power amplifier circuitry  20 . As shown by curves  64  and  66 , by increasing the supply voltage provided to power amplifier circuitry  20 , the power levels of in-band emissions produced by device  10  may be reduced to levels that are below P IN-BAND  while maintaining output transmission power levels at desired output level P out  (e.g., because the linearity of power amplifier circuitry  20  may be improved by increasing the supply voltage). 
     It may be desirable to minimize the power consumed by wireless device  10  while maintaining satisfactory performance. For example, device  10  may be a mobile device that receives power from a battery or other power source that may have a limited amount of available power. In this scenario, it may be desirable to improve battery life by minimizing power consumption while satisfying in-band emissions requirements and adjacent channel emissions requirements. Electronic device  10  may therefore provide the optimal power supply voltage represented by curve  64  to power amplifier circuitry  20  (e.g., a minimum power supply voltage that produces acceptable in-band emissions levels). 
     The amount of undesired signal power produced on frequencies outside of the transmission frequency range may vary based on the bandwidth of the frequency range. As an example, intermodulation between transmit frequencies may accumulate with increased transmission bandwidth. It may be desirable to optimize the power supply voltage provided to power amplifier circuitry  20  based on the number of resource blocks allocated to device  10  (e.g., because each additional resource block may increase the frequency range of radio-frequency transmissions and thereby increase undesired radio-frequency emissions). 
       FIG. 5  shows a scenario in which wireless electronic device  10  may adjust the power amplifier supply voltage based on the number of resource blocks (e.g., resource blocks  52  of  FIG. 4 ) that are assigned to device  10 . In the example of  FIG. 5 , device  10  may be assigned most of the available resource blocks. The resource blocks assigned to device  10  may cover a frequency range  72  that covers almost all of the available bandwidth in channel  54  (e.g., frequency range  72  may include most of the frequencies between f L  and f H ). As an example, frequency range  72  may occupy 48 of 50 available resource blocks, leaving two unallocated resource blocks  52 C at the edges of channel  54 . 
     Curve  74  shows an illustrative output power spectrum of device  10  that provides power amplifier circuitry  20  with a first power supply voltage (e.g., 2.0 V). As shown by curve  74 , at the first power supply voltage, power amplifier circuitry  20  may produce acceptable power levels in resource blocks  52  that are not allocated to device  10  (e.g., power levels of signals produced in resource blocks  52 C may be less than P IN-BAND  and satisfy in-band emissions requirements). However, power amplifier circuitry  20  may produce out-of-channel signals (e.g., radio-frequency signals with frequencies less than f L  or greater than f H ) that have unacceptable power levels. For example, adjacent channel leakage requirements may be more restrictive than in-band emissions requirements (e.g., P ACLR  may be less than P IN-BAND ) and power amplifier circuitry  20  may produce power level P 1  at frequency f 1  that violates adjacent channel leakage ratio (ACLR) requirements (e.g., P 1  may be greater than P ACLR ). 
     To reduce out-of-channel emissions to acceptable power levels, wireless electronic device  10  may adjust the power amplifier supply voltage to control the linearity of power amplifier circuitry  20 . For example, wireless electronic device  10  may adjust power supply circuitry  38  to increase supply voltage Vcc provided to power amplifier circuitry  20 , thereby improving the linearity of power amplifier circuitry  20  and reducing out-of-channel emissions. 
     Curve  76  shows an illustrative output power spectrum for a device  10  that provides a second power amplifier supply voltage to power amplifier circuitry  20 . The second power amplifier supply voltage may correspond to an optimal supply voltage that device  10  may provide to power amplifier circuitry  20  to satisfy emissions requirements while minimizing power consumption. As shown by curve  76 , power amplifier circuitry  20  may produce output power levels that satisfy in-band emissions requirements and out-of-channel emissions requirements. In other words, by increasing the supply voltage provided to power amplifier circuitry  20 , device  10  may reduce wireless emissions in frequencies outside of allocated frequency range  72  to acceptable levels. For example, at the optimal operating supply voltage of curve  76 , power amplifier circuitry  20  may produce radio-frequency signals with power level P 2  at frequency f 1 . Power P 2  may be sufficiently low to satisfy adjacent channel leakage ratio requirements and in-band emissions requirements (e.g., P 2  may be less than P ACLR  and P IN-BAND ). At the optimal power amplifier supply voltage of curve  76 , the maximum output power level for any frequency outside of frequency range  72  may be less than P ACLR  and P IN-BAND . 
     The location of resource blocks within a frequency channel (band) may determine the required linearity of power amplifier circuitry  20 .  FIG. 6  shows an illustrative scenario in which a device  10  that is allocated resource blocks within a frequency range  82  near the boundaries of channel  54  may be subject to more restrictive linearity requirements (e.g., relative to a device  10  such as shown in  FIG. 4  that is allocated resource blocks closer to the center frequencies of channel  54 ). 
     In the example of  FIG. 6 , curves  84  and  86  represent output power spectrums of device  10  with a power amplifier circuitry  20  operating at respective first and second supply voltages. For example, curve  84  may correspond to a first supply voltage of 2 volts and curve  86  may correspond to a second supply voltage of 2.9 volts. 
     As shown by curve  84 , the in-band output power produced by power amplifier circuitry  20  at the first supply voltage may satisfy in-band emissions requirements (e.g., output power produced by device  10  may be less than P IN-BAND  for frequencies within channel  54 ). However, because transmission frequency range  82  is relatively close to the edge of channel  54 , device  10  may produce output power levels that exceed adjacent channel leakage ratio requirements. For example, device  10  may produce output power level P 3  at frequency f 2  that exceeds P ACLR  (e.g., the maximum power allowed by adjacent channel leakage ratio requirements). 
     To satisfy adjacent channel leakage ratio requirements, device  10  may improve power amplifier linearity by increasing the power amplifier supply voltage to the second supply voltage, thereby producing the output power levels corresponding to curve  86 . As shown by curve  86 , at the second supply voltage, device  10  may produce output power levels that satisfy both in-band emissions requirements and adjacent channel leakage ratio requirements (e.g., device  10  may produce output power levels that are below P IN-BAND  for frequencies between f L  and f H  and output power levels that are below P ACLR  for frequencies less than f L  or greater than f H ). 
     Wireless electronic device  10  may include components that undesirably change signal properties of the output signal produced by power amplifier circuitry  20 . For example, output signals that pass through duplex filter (duplexer)  28  as shown in  FIG. 2  may be attenuated due to insertion loss of duplexer  28 . Duplexer  28  may attenuate the radio-frequency output of power amplifier circuitry  20  based on the frequencies of the output.  FIG. 7  shows a diagram illustrating how duplexer insertion loss may change based on output signal frequencies. 
     Resource blocks  52 D and  52 E may correspond to respective frequency ranges. As shown in  FIG. 7 , the insertion loss introduced by duplexer  28  at the frequency range corresponding to resource block  52 D may be approximately L 1  and the insertion loss introduced by duplexer  28  at the frequency range corresponding to resource block  52 E may be approximately L 2 . L 1  may be less than L 2  (e.g., the duplexer may introduce less power loss for resource block  52 D than  52 E). 
     The frequency dependent insertion loss introduced by duplexer  28  may affect the relative power levels between a transmitted signal and undesired signals produced by power amplifier nonlinearity. For example, a relatively low duplexer insertion loss L 1  for resource block  52 D may allow device  10  to achieve a desired output power level without increasing amplifier linearity (e.g., because in-band emissions may be attenuated by relatively high insertion loss). Device  10  may reduce the power supply voltage (e.g., Vcc) provided to power amplifier circuitry  20  when device  10  is allocated resource blocks that correspond to frequencies associated with relatively low duplexer insertion loss. Device  10  may increase the power supply voltage (thereby increasing power amplifier linearity) when device  10  is allocated resource blocks associated with relatively high duplexer insertion loss. In this way, power consumption may be minimized while satisfying emissions requirements. 
     To minimize power consumption while ensuring that power emissions requirements are satisfied, device  10  may be provided with calibration table  92  of  FIG. 8 . Table  92  may be stored at locations such as storage and processing circuitry  16 . Table  92  may include entries that identify optimal supply voltages based on desired transmission output power levels and resource blocks that are allocated to device  10 . Higher output power ranges may be assigned optimal supply voltages that are larger than supply voltages assigned to lower output ranges (e.g., because transmitting radio-frequency signals at a relatively high output power level may cause non-linear operation such as clipping). For example, in an output power range of 20-24 dBm, power amplifier circuitry  20  may be provided with a power supply voltage of 2.9 V, while in an output power range of 0-10 dBm, power amplifier circuitry  20  may be provided with a power supply voltage of 1.5 V. 
     In the example of  FIG. 8 , the number of allocated resource blocks may range from one resource block to n resource blocks (e.g., any desirable number of resource blocks within the frequency band) and the allocated resource block location within the frequency band may range from location zero to location m (e.g., any desirable location within the frequency band). 
     The entries of table  92  may identify optimal power amplifier supply voltages based on the number of allocated resource blocks, the locations of the allocated resource blocks within an operating channel, and frequency dependent power loss (e.g., as introduced by components such as duplexer  28 ). The optimal power amplifier supply voltages may be selected to minimize power consumption while power emissions requirements such as adjacent channel leakage ratio requirements and/or in-band emissions requirements are satisfied. 
     To optimize supply voltage Vcc provided to power amplifier circuitry  20  while communicating with a base station  6  on a frequency channel, a wireless electronic device  10  may perform the illustrative steps shown in  FIG. 9 . 
     In step  102 , wireless electronic device  10  may inform base station  6  of data to be transmitted. For example, wireless electronic device  10  may communicate with a base station  6  using a network standard that allocates resource blocks to devices for transmitting data (e.g., using the LTE standard that allocates resource blocks  52  to device  10 ). In this scenario, wireless electronic device  10  may inform base station  6  of data to be transmitted from device  10  to base station  6 . 
     In step  104 , base station  6  may allocate resource blocks to wireless electronic device  10  and inform device  10  of the allocated resource blocks. As examples, base station  6  may allocate four resource blocks located at the center of a frequency channel, 30 resource blocks of the frequency channel, 12 resource blocks located at the end of the frequency channel, or any other desirable number of available resource blocks within the frequency channel. 
     In step  106 , wireless electronic device  10  may optimize the power amplifier supply voltage based on a desired output power and the allocated resource blocks to minimize power consumption while satisfying emissions requirements (e.g., to satisfy in-band emissions requirements and to satisfy adjacent channel leakage requirements). If desired, device  10  may use calibration values stored in storage and processing circuitry  16  (e.g., values stored in entries of table  92 ) to optimize the power amplifier supply voltage. For example, device  10  may retrieve an entry of table  92  that identifies an optimal power supply voltage for the desired transmission output power, the number of allocated resource blocks, and the location of the allocated resource blocks within a frequency channel. 
     In step  108 , wireless electronic device  10  may transmit the data to the base station using the resource blocks allocated to the device and while providing the optimized supply voltage to power amplifier circuitry  20 . The process may then loop back to step  102  to continuously optimize power supply voltages based on resource block allocation. 
     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: 20110906
Publication Date: 20150630
Grant Date: 20150630
Priority Date: 20110906
Inventors: LUM NICHOLAS W.
NOELLERT WILLIAM J.
DIMPFLMAIER RONALD W.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B1/0475", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/0475", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 47753520