HK1190004B - Apparatus and methods for envelope tracking calibration - Google Patents

Description

Apparatus and method for envelope tracking calibration

Technical Field

Embodiments of the present invention relate to electronic systems, and more particularly, to Radio Frequency (RF) electronics.

Background

A power amplifier may be included in a mobile phone to amplify an RF signal for transmission. For example, in mobile phones with Time Division Multiple Access (TDMA) architectures, such as those found in the global system for mobile communications (GSM), Code Division Multiple Access (CDMA), and wideband code division multiple access (W-CDMA) systems, power amplifiers may be used to amplify RF signals for transmission via an antenna. Managing the amplification of RF signals is important because the desired transmit power level may depend on how far the user is from the base station and/or the mobile environment. Power amplifiers may also be used to help adjust the power level of an RF signal over time to avoid signal interference from transmissions during an assigned receive timeslot.

The power efficiency of a power amplifier at a particular input power level may be a function of various factors including circuit components and layout, power amplifier load, and/or power amplifier supply voltage. To help improve the efficiency of the power amplifier, a technique known as envelope tracking may be used in which the level of the power supply to the power amplifier is varied with respect to the envelope of the RF signal. Therefore, when the envelope of the RF signal increases, the voltage supplied to the power amplifier may increase. Likewise, when the envelope of the RF signal decreases, the voltage supplied to the power amplifier may decrease, thereby reducing power consumption.

Disclosure of Invention

In certain embodiments, the present disclosure relates to a method of calibrating an envelope tracking system. The method includes generating a supply voltage for the power amplifier using an envelope tracker having an envelope shaping table generated at a desired gain compression of the power amplifier. The method also includes operating a supply voltage of the power amplifier at a first voltage level associated with substantially no-gain compression of the power amplifier. The method further includes measuring an output power of the power amplifier at a first voltage level; reducing the voltage level of the supply voltage one or more times and measuring the output power at each voltage level; determining a second voltage level of the power amplifier associated with a gain compression approximately equal to the desired gain compression; and calibrating the envelope tracker based on the determination.

In various embodiments, the method further comprises scaling an amplitude of the envelope signal to generate a scaled envelope signal, the supply voltage being generated based at least in part on the scaled envelope signal.

In some embodiments, the envelope shaping table comprises shaping data relating a plurality of scaled envelope signal amplitudes to a plurality of supply voltage levels.

In many embodiments, the method further comprises generating the supply voltage from the battery voltage using the shaped data and the scaled envelope signal.

According to several embodiments, the shaping data is in a digital format, and the method further comprises converting the shaping data to an analog format.

In some embodiments, reducing the voltage level of the supply voltage includes changing calibration data of the envelope tracker to reduce the supply voltage.

In some embodiments, calibrating the envelope tracker based on the determination includes selecting a value of the calibration data that is approximately equal to a value of the calibration data corresponding to the second voltage level.

According to many embodiments, scaling the amplitude of the envelope signal comprises multiplying the envelope signal by a scaling factor determined at least in part by the calibration data.

In various embodiments, the scaling factor is also determined by a power control signal from the transceiver.

In some embodiments, measuring the output power of the power amplifier at the first voltage level includes measuring the output power using a directional coupler and a power detector electrically coupled to an output of the power amplifier.

In many embodiments, the first voltage level is approximately equal to the maximum supply voltage of the power amplifier.

According to several embodiments, reducing the voltage level of the supply voltage one or more times comprises reducing the level in discrete steps.

In various embodiments, reducing the level of the supply voltage one or more times and measuring the output power at each voltage level includes continuously reducing the voltage level and measuring the output power at a plurality of discrete voltage levels.

In certain embodiments, the present disclosure relates to a computer-readable storage medium comprising instructions that, when executed by a processor, perform a method of calibrating an envelope tracking system. The method includes generating a supply voltage for a power amplifier using an envelope tracker having an envelope shaping table generated at a desired gain compression of the power amplifier. The method also includes operating a supply voltage of the power amplifier at a first voltage level associated with substantially no-gain compression of the power amplifier. The method further comprises measuring an output power of the power amplifier at a first voltage level; reducing the voltage level of the supply voltage one or more times and measuring the output power at each voltage level; determining a second voltage level of the power amplifier associated with a gain compression approximately equal to the desired gain compression; and calibrating the envelope tracker based on the determination.

In certain embodiments, the present disclosure relates to a power amplifier system comprising: a power amplifier; and an envelope tracker configured to generate a supply voltage of the power amplifier. The envelope tracker includes a shaping module having an envelope shaping table generated at a desired gain compression of the power amplifier; and a scaling module configured to scale the amplitude of the envelope signal and to provide the scaled envelope signal amplitude to the shaping module. The power amplifier further includes: a directional coupler electrically connected to an output of the power amplifier; a power detector electrically connected to the directional coupler and configured to measure an output power of the power amplifier using the directional coupler; and a calibration module configured to provide calibration data to the scaling module to thereby vary the scaled envelope signal amplitude generated by the scaling module. The calibration module is configured to set the calibration data to a first value corresponding to a voltage level of the supply voltage associated with substantially no gain compression and to reduce the voltage level of the supply voltage by changing the calibration data until the power detector indicates that the gain compression of the power amplifier is approximately equal to the desired gain compression.

In various embodiments, the envelope shaping table includes shaping data relating a plurality of scaled envelope signal amplitudes to a plurality of supply voltage levels.

In some embodiments, the power amplifier system further comprises a modulator configured to generate the supply voltage from the battery voltage using the shaping data.

In many embodiments, the power amplifier system further comprises a digital-to-analog converter for converting the shaped data to analog data for use by the modulator.

According to several embodiments, the power amplifier system further comprises a power control module electrically connected to the power detector.

In some embodiments, the scaling module is further configured to receive a power control signal from the power control module and to vary the scaled envelope signal amplitude using the power control signal.

In some embodiments, the scaling module is configured to multiply the calibration data by the power control signal to generate a scaling factor and to multiply the amplitude of the envelope signal by the scaling factor to generate a scaled envelope signal amplitude.

In various embodiments, the first value of the calibration data corresponds to about a maximum supply voltage of the power amplifier.

In some embodiments, the power amplifier further comprises a duplexer having an input electrically connected to the output of the power amplifier and the directional coupler, and an output electrically connected to the antenna.

In certain embodiments, the present disclosure relates to a method of calibrating a power amplifier system. The method includes generating a supply voltage for the power amplifier using an envelope tracker having an envelope shaping table generated at a desired gain compression of the power amplifier. The method also includes operating a supply voltage of a power amplifier at a first voltage level and a first input power level associated with a target power of the power amplifier. The method also includes measuring an output power of the power amplifier at a first input power level to determine a power gain; increasing the input power of the power amplifier one or more times and measuring the output power at each input power level; determining a second input power level corresponding to a gain compression of the power amplifier approximately equal to the desired gain compression; and calibrating the power amplifier system based on the determination.

In various embodiments, the method further comprises using the calibration data to change a gain of a variable gain amplifier configured to drive an input of the power amplifier.

In some embodiments, increasing the input power of the power amplifier one or more times comprises changing the calibration data to increase the gain of the variable gain amplifier one or more times.

In many embodiments, calibrating the power amplifier system based on the determination includes selecting a value of the calibration data that is approximately equal to a value of the calibration data corresponding to the second input power level.

In some embodiments, the method further comprises using a power control signal from the transceiver to further control the gain of the variable gain amplifier.

According to many embodiments, the method further comprises controlling the gain of the variable gain amplifier by multiplying the calibration data by the power control signal.

In several embodiments, measuring the output power of the power amplifier at the first input power level to determine the power gain includes measuring the output power using a directional coupler and a power detector electrically coupled to an output of the power amplifier.

In certain embodiments, the present disclosure relates to a computer-readable storage medium comprising instructions that, when executed by a processor, perform a method of calibrating a power amplifier. The method includes generating a supply voltage for a power amplifier using an envelope tracker having an envelope shaping table generated at a desired gain compression of the power amplifier. The method also includes operating a supply voltage of a power amplifier at a first voltage level and a first input power level associated with a target power of the power amplifier. The method also includes measuring an output power of the power amplifier at a first input power level to determine a power gain; increasing the input power of the power amplifier one or more times and measuring the output power at each input power level; determining a second input power level corresponding to a gain compression of the power amplifier approximately equal to the desired gain compression; and calibrating the power amplifier system based on the determination.

In certain embodiments, the present disclosure relates to a power amplifier system comprising a power amplifier; a variable gain amplifier configured to drive an input of the power amplifier; and an envelope tracker configured to generate a supply voltage for the power amplifier. The envelope tracker includes an envelope shaping table generated at a desired gain compression of the power amplifier. The power amplifier system further includes a directional coupler electrically connected to an output of the power amplifier; a power detector electrically connected to the directional coupler and configured to measure an output power of the power amplifier using the directional coupler; and a calibration module configured to provide calibration data to the variable gain amplifier to control an input power of the power amplifier. The calibration module is configured to set the calibration data to a first value corresponding to the voltage level of the supply voltage and the input power of the power amplifier associated with the target power of the power amplifier, and to increase the input power of the power amplifier by changing the calibration data until the power detector indicates that the gain compression of the power amplifier is approximately equal to the desired gain compression.

In various embodiments, the power amplifier system further comprises a power control module electrically connected to the power detector.

In some embodiments, the power control module is configured to generate a power control signal for controlling the gain of the variable gain amplifier.

In many embodiments, the power amplifier system includes a multiplier for multiplying the calibration data by the power control signal to generate a gain control signal for controlling the gain of the variable gain amplifier.

According to some embodiments, the power amplifier system further comprises a duplexer having an input electrically connected to the output of the power amplifier and the directional coupler, and an output electrically connected to the antenna.

Drawings

Fig. 1 is a schematic block diagram of an example wireless device that may include one or more power amplifier modules.

Fig. 2 is a schematic block diagram of one example of a power amplifier system with an envelope tracker.

Fig. 3A-3B show two examples of power supply voltage versus time.

Fig. 4 is a schematic block diagram of another example of a power amplifier system with an envelope tracker.

Fig. 5 is a graph of supply voltage and gain versus input power for one example.

Fig. 6 is a schematic block diagram of a power amplifier system according to an embodiment.

Fig. 7 is a schematic block diagram of a power amplifier system according to another embodiment.

Fig. 8 is a flow diagram illustrating calibration of a power amplifier system according to one embodiment.

Fig. 9 is a flow chart illustrating calibrating a power amplifier system according to another embodiment.

Detailed description of the preferred embodiments

Any headings, if any, provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.

When the power amplifier supply voltage is varied with respect to the envelope of the RF signal, it can be difficult to maintain certain performance characteristics of the power amplifier. For example, variations in the inter-component variation (part-to-part component variation) in the system can produce misalignment (mismatch) between the envelope voltage and the associated power supply voltage generated by the envelope tracker, thereby making it difficult to maintain relatively constant gain compression when tracking the envelope signal over a wide dynamic range. Although the power amplifier may be calibrated to try to compensate for this error, the calibration may be complicated by variations in the DC bias voltage, insertion loss, and/or gain in the envelope and signal path.

There is a need for an improved power amplifier. Furthermore, there is a need for an improved apparatus and method for envelope tracking calibration.

Fig. 1 is a schematic block diagram of an example wireless device 11 that may include one or more power amplifier modules. The wireless device 11 may include a power amplifier implementing one or more features of the present disclosure.

The example wireless device 11 depicted in fig. 1 may represent a multi-band and/or multi-mode device such as a multi-band/multi-mode mobile phone. As an example, the Global System for Mobile (GSM) communications standard is a model of digital cellular communications used in many parts of the world. GSM mode mobile phones can operate in one or more of the following four frequency bands: 850MHz (about 824-. Variants of the GSM band and/or regional/national implementations are also used in different parts of the world.

Code Division Multiple Access (CDMA) is another standard that may be implemented in mobile telephone devices. In some embodiments, CDMA devices may operate in one or more of the 800MHz, 900MHz, 1800MHz, and 1900MHz bands, while some WCDMA and Long Term Evolution (LTE) devices may operate over, for example, approximately 22 radio spectrum bands.

One or more features of the present disclosure may be implemented in the previous example modes and/or frequency bands, as well as in other communication standards. For example, 3G, 4G, LTE, and LTE-advanced are non-limiting examples of such standards.

In some embodiments, wireless device 11 may include a duplexer 12, a transceiver 13, an antenna 14, a power amplifier 17, a control component 18, a computer-readable medium 19, a processor 20, a battery 21, and an envelope tracker 22.

The transceiver 13 may generate an RF signal for transmission via the antenna 14. In addition, the transceiver 13 may receive incoming RF signals from the antenna 14.

It should be understood that various functions associated with the transmission and reception of RF signals may be implemented by one or more components collectively represented in fig. 1 as transceiver 13. For example, the transmit and receive functions may be provided by separate components.

Likewise, it should be understood that various antenna functions associated with the transmission and reception of RF signals may be implemented by one or more components collectively represented in fig. 1 as antenna 14. For example, a single antenna may be configured to provide both transmit and receive functions. In yet another example, the transmit and receive functions may be provided by separate antennas. In yet another example, different bands associated with wireless device 11 may be equipped with one or more antennas.

In fig. 1, one or more signals from transceiver 13 are depicted as being provided to antenna 14 via one or more transmission paths 15. In the illustrated example, the different transmission paths 15 may represent output paths associated with different bands and/or different power outputs. For example, the two example power amplifiers 17 shown may represent amplification associated with different power output configurations (e.g., low power output and high power output), and/or amplification associated with different bands. Although fig. 1 shows the wireless device 11 as including two transmission paths 15, the wireless device 11 may be adapted to include more or fewer transmission paths 15.

In fig. 1, one or more detected signals from antenna 14 are depicted as being provided to transceiver 13 via one or more receive paths 16. In the illustrated example, the different receive paths 16 may represent paths associated with different bands. For example, the four example paths 16 shown may represent four-band capabilities provided by some wireless devices. Although fig. 1 shows the wireless device 11 as including four receive paths 16, the wireless device 11 may be adapted to include more or fewer receive paths 16.

To facilitate switching between receive and transmit paths, the duplexer 12 may be configured to electrically connect the antenna 14 to a selected transmit or receive path. Thus, the duplexer 12 may provide a number of switching functions associated with the operation of the wireless device 11. In some embodiments, the duplexer 12 may include a number of switches configured to provide functionality associated with, for example, switching between different bands, switching between different power modes, switching between transmit and receive modes, or some combination thereof. The duplexer 12 may also be configured to provide additional functions, including filtering of signals.

Fig. 1 illustrates that in certain embodiments, a control component 18 may be provided, which control component 18 may be configured to provide various control functions associated with the operation of the duplexer 12, power amplifier 17, envelope tracker 22, and/or other operational components. Non-limiting examples of the control assembly 18 are described in more detail herein.

In certain embodiments, processor 20 may be configured to facilitate the various processes described herein. For purposes of description, embodiments of the present disclosure may also be described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. The computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the actions specified in the flowchart and/or block diagram block or blocks.

In certain embodiments, these computer program instructions may also be stored in a computer-readable memory 19, which computer-readable memory 19 may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the action specified in the flowchart and/or block diagram block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the actions specified in the flowchart and/or block diagram block or blocks.

The illustrated wireless device 11 also includes an envelope tracker 22 that may be used to provide a power supply voltage to the one or more power amplifiers 17. For example, the envelope tracker 22 may be configured to control the supply voltage to be provided to the power amplifier 17 based on the envelope of the RF signal to be amplified.

The envelope tracker 22 may be electrically connected to the battery 21, and the envelope tracker 22 may be configured to vary or change the voltage provided to the power amplifier 17 based on the envelope of the RF signal to be amplified. The battery 21 may be any suitable battery for use in the wireless device 11, including, for example, a lithium ion battery. As will be described in detail below, by controlling the voltage supplied to the power amplifier, the power consumption of the battery 21 may be reduced, thereby improving the performance of the wireless device 11. The envelope signal may be provided from the transceiver 13 to the envelope tracker 22. However, the envelope signal may be determined in other ways. For example, the envelope signal may be determined by detecting the envelope of the RF signal using any suitable envelope detector.

Fig. 2 is a schematic block diagram of one example of a power amplifier system 50 having an envelope tracker. The illustrated power amplifier system 50 includes a battery 21, a power amplifier 32, a multi-level supply module 51, a supply voltage selection module 52, and a supply voltage adjustment module 54. As will be described below, the multi-level supply module 51, the supply voltage selection module 52 and the supply voltage adjustment module 54 may collectively operate as an envelope tracker configured to vary or vary the power supply voltage V with respect to the envelope signal_CC。

Power amplifier 32 includes a receiver configured to receive RF signals RF_INAnd is configured to generate an amplified RF signal RF_OUTTo output of (c). Furthermore, the power supply voltage V is used_CCPower amplifier 32 is powered.

The multi-level supply module 51 may generate multiple power supplies from the battery 21. For example, the multi-level supply module 51 may be used to generate n supplies from the battery 21, where n is an integer. Each supply generated by the multi-level supply module 51 may have a level greater than, less than, or equal to the battery voltage. In one embodiment, the multi-level supply module 51 includes a buck-boost converter.

Supply voltage selection module 52 may receive RF signals RF_INAnd may be selected among the supplies generated by the multi-level supply module 51 to provide the supply voltage regulation module 54 with the most appropriate information for tracking the envelopeSupply voltage level of sign. For example, supply voltage selection module 52 may provide supply voltage to supply voltage adjustment module 54 in a relatively small amount that is greater than the envelope voltage. Thereafter, supply voltage adjustment module 54 may provide relatively fine-tuned adjustment of the supply voltage to generate envelope tracking power supply voltage V_CC. By including the multi-level supply block 51, the supply voltage selection block 52 and the voltage regulation block 54, limitations on the design of the envelope tracking system may be reduced, thereby allowing for a system with greater flexibility and improved power efficiency relative to a scheme employing only a single tracking or selection block.

As shown in fig. 2, supply voltage regulation module 54 may be electrically connected in a feedback arrangement to help reinforce power supply V with respect to the envelope of the RF signal_CCThe tracking of (2). Supply voltage regulation module 54 may include one or more amplifiers configured to provide linear tracking of the envelope signal to generate power supply voltage V_CC. In some embodiments, one or more amplifiers may be electrically connected with one or more adders to help generate an error signal that may be added to the supply voltage selected by supply voltage selection module 52. Although FIG. 2 shows a configuration in which the power supply voltage V is supplied_CCA feedback arrangement is provided as an input back to the supply voltage regulation module 54, but in some embodiments a feed-forward arrangement may be used.

Although not shown in fig. 2, the power amplifier system 50 may include a delay block to compensate for generating the power supply voltage V_CCThe delay of (2). For example, the delay block may be included in the RF signal RF_INAnd the input of power amplifier 32 to assist the signal amplified by power amplifier 32 with the power supply voltage V_CCAnd (6) aligning.

Fig. 3A-3B show two examples of power supply voltage versus time.

In fig. 3A, graph 47 shows the RF signal 41 and the voltage of the power amplifier supply 43 versus time. The RF signal 41 has an envelope 42.

The power supply voltage 43 of the power amplifier may be configured to have a voltage greater than the voltage of the RF signal 41. For example, providing a supply voltage to the power amplifier having a voltage magnitude less than the voltage magnitude of the RF signal 41 may clip (clip) the RF signal, thereby creating signal distortion and/or other problems. Thus, the power supply voltage 43 may be selected to have a voltage magnitude that is larger than the voltage magnitude of the envelope 42 of the RF signal 41. However, it may be desirable to reduce the voltage difference between the supply voltage 43 and the envelope 42 of the RF signal 41, as the area between the power amplifier supply 43 and the envelope 42 of the RF signal 41 may represent lost energy, which may reduce battery life and increase the amount of heat generated in the mobile device.

In fig. 3B, graph 48 shows the RF signal 41 and the voltage of the power amplifier supply 44 versus time. Unlike the power amplifier supply 43 of fig. 3A, the power amplifier supply 44 of fig. 3B varies with respect to the envelope 42 of the RF signal 41. The region between the power amplifier supply 44 and the envelope 42 of the RF signal 41 in fig. 3B is smaller than the region between the power amplifier supply 43 and the envelope 42 of the RF signal 41 in fig. 3A, and thus the graph 48 in fig. 3B may be associated with a power amplifier system with higher energy efficiency. Fig. 3B may represent the output of one example of an envelope tracking system, such as the envelope tracking system described herein.

Fig. 4 is a schematic block diagram of yet another example of a power amplifier system 60 having an envelope tracker 22. The illustrated power amplifier system 60 includes the envelope tracker 22, the power amplifier 32, the inductor 62, the bypass capacitor 63, the impedance matching block 64, the duplexer 12, and the antenna 14.

The power amplifier 32 may receive the RF signal RF_INAnd generates an amplified RF signal RF_OUT. The envelope tracker may receive the RF signal RF_INAnd may generate a power amplifier supply voltage V for power amplifier 32 that tracks the envelope signal_CC。

The illustrated power amplifier 32 includes a bipolar transistor 61 having an emitter, a base, and a collector. Bipolar crystalThe emitter stage of the tube 61 may be electrically connected to a first voltage supply V₁Which may be, for example, a ground supply (ground supply) or a node. Furthermore, the RF input signal RF_INMay be provided to the base of the bipolar transistor 61. The bipolar transistor 61 may amplify the RF signal RF_INTo generate an amplified RF signal RF at the collector_OUT. The bipolar transistor 61 may be any suitable device. In one embodiment, the bipolar transistor 61 is a Heterojunction Bipolar Transistor (HBT).

Power amplifier 32 may be configured to provide amplified RF signal RF to duplexer 12_OUT. An impedance matching block 64 may be used to help terminate the electrical connection between the power amplifier 32 and the duplexer 12. For example, the impedance matching block 64 may be used to increase power transfer and/or decrease the amplified RF signal RF_OUTIs reflected. In some embodiments, inductor 62 may be configured to operate as part of impedance matching block 64.

An inductor 62 may be included to help bias the power amplifier 32 to the power amplifier supply voltage Vcc generated by the envelope tracker 22. The inductor 62 may comprise a first terminal electrically connected to the envelope tracker 22 and a second terminal electrically connected to the collector of the bipolar transistor 61. Bypass capacitor 63 may have an electrical connection to power supply V_CCAnd is electrically connected to a first voltage supply V₁And may perform a variety of functions. For example, the inclusion of bypass capacitor 63 may reduce supply voltage V_CCAnd/or stabilize the output of power amplifier 32. In addition, a bypass capacitor 63 may be used to provide RF and/or AC ground for inductor 62.

Although fig. 4 illustrates one embodiment of power amplifier 32, those skilled in the art will appreciate that the teachings described herein are applicable to a wide variety of power amplifier configurations, including, for example, multi-stage power amplifier configurations and power amplifiers employing other transistor configurations. For example, in some embodiments, the bipolar transistor 61 may be omitted and a Field Effect Transistor (FET), such as a silicon FET, gallium arsenide (GaAs) High Electron Mobility Transistor (HEMT), or a Lateral Diffusion Metal Oxide Semiconductor (LDMOS) transistor may be employed.

Fig. 5 is a graph 70 showing one example of supply voltage and gain versus input power. The graph 70 includes a first curve 71 showing the power supply voltage of the power amplifier in volts versus the input power in dBm. Curve 70 also includes a second curve 72 showing power amplifier gain in dB versus power amplifier input power in dBm for the power amplifier.

The first and second curves 71, 72 show that the gain of the power amplifier may be kept relatively constant when the input power is increased by increasing the power supply voltage level of the power amplifier relative to the input power. For example, by increasing the power supply voltage from about 1V to about 6V while increasing the input power level from about-15 dBm to about 22dBm, the gain shown in the second curve 72 remains relatively constant at an amplitude of about 13.25 dB.

When performing envelope tracking, a relatively constant gain compression of the power amplifier may be maintained by controlling the difference between the power supply voltage level and the input power of the envelope signal. To help control the magnitude of the power supply voltage relative to the magnitude of the envelope signal, the envelope tracker may include an envelope shaping table (profiling table) generated at target gain compression that includes data relating a plurality of desired voltage supply magnitudes to a plurality of envelope signal magnitudes.

When using an envelope shaping table, part-to-part variations in components in the power amplifier system may introduce variations that may produce misalignment between the generated power supply voltage and the actual input power. For example, bias voltage, power amplifier gain error, and/or various other factors may cause misalignment between the magnitude of the power supply and the input power of the envelope signal. For various reasons, it is difficult to compensate for these errors using conventional calibration techniques. For example, the power amplifier may include a duplexer electrically connected between the output of the power amplifier and the antenna, and variations in insertion loss of the duplexer may make it difficult to correlate the power measurement at the antenna with the power supply voltage of the power amplifier. Thus, duplexer loss uncertainty and/or other losses between the power amplifier output and the antenna may complicate calibration.

To accommodate (acomod) inter-part variation and/or other contributing factors to envelope magnitude misalignment, the power amplifier system may be designed to include a margin (margin) to account for envelope magnitude misalignment errors. For example, gain compression may exist around the maximum output power level of the amplifier, and may introduce distortion in the RF signal, and the power amplifier may be operated at an increased power supply voltage to provide additional active space (headroom) to prevent distortion. However, increasing the power supply voltage reduces the efficiency of the power amplifier.

There is a need to improve the calibration of power amplifier systems to increase power amplifier efficiency and to avoid distortion of the amplified RF signal due to envelope amplitude misalignment. Additionally, there is a need for a calibration scheme with relatively fast calibration times, thereby reducing calibration costs in a factory setting and/or allowing dynamic use of calibration methods in a mobile device operating environment. Additionally, there is a need for an improved calibration system that can account for duplexer loss uncertainty and/or loss between the output of the power amplifier and the antenna.

Fig. 6 is a schematic block diagram of a power amplifier system 98 in accordance with one embodiment. The power amplifier system 98 includes a duplexer 12, a transceiver 13, an antenna 14, a battery 21, an envelope tracker 22, a power amplifier input stage or Variable Gain Amplifier (VGA) 31, a power amplifier 32, and a directional coupler 88.

The illustrated envelope tracker 22 includes a calibration module 80, a scaling module 81, a shaping table module 82, a digital-to-analog converter 83, a modulator 84, and a multiplier 87. The illustrated transceiver 13 includes a power control module 85 and a power detector 86. As will be described in detail below, the calibration module 80 of the envelope tracker 22 may be used to calibrate the envelope tracker 22 to accommodate envelope magnitude misalignments.

The transceiver 13 is shown configured to provide an envelope signal to the envelope tracker 22 and an RF signal RF to the VGA31_IN. The transceiver 13 includes a power control module 85 that may be used to adjust the power level of the power amplifier system 98. For example, the power control module 85 may provide a first power control signal or Gain Control Level (GCL) to the VGA31, which may be used to control the gain of the VGA 31. In addition, the power control module 85 may provide a second power control signal or Power Control Level (PCL) to the envelope tracker 22, which may be used to scale the amplitude of the envelope signal. Power control module 85 may be used to control the power level of power amplifier system 98 and/or control other power settings over various power modes, as well as to compensate for various systems and/or operational parameters that may affect power performance.

To help enhance the accuracy of the power control module 85, the transceiver 13 may include a power detector 86. The power detector 86 may be electrically coupled to a directional coupler 88 at the output of the power amplifier 32 to improve the accuracy of the output power measurement. For example, directional coupler 88 may be located between the output of power amplifier 32 and the input of duplexer 12, thereby allowing power detector 86 to generate a power measurement that does not include the insertion loss of duplexer 12. However, in some embodiments, the directional coupler 88 need not be located directly at the output of the power amplifier 32. For example, fig. 6 has shown in phantom an alternate location of the directional coupler 88 between the duplexer 12 and the antenna 14.

The scaling module 81 may receive a Power Control Level (PCL) from the power control module 85 and may scale the amplitude of the envelope signal using the PCL. The scaled or amplified envelope signal may be provided to a shaping table module 82, which may include a shaping table having shaping data relating a plurality of scaled envelope signal amplitudes to a plurality of target supply voltage levels. The shaping table may be generated at a particular target gain compression, as described above with reference to fig. 5.

The shaping table module 82 may generate a signal including data indicative of the desired supply voltage level and provide the signal to the modulator 84. In embodiments where the signal is in a digital format, such as in a configuration where the signal corresponds to an entry from a shaping table, a digital-to-analog converter 83 may be used to convert the signal to an analog format. The modulator 84 may be electrically connected to the battery 21 and may use data related to the target supply voltage level from the shaping table module 82 to generate the power supply voltage V for the power amplifier 32_CC。

The envelope tracker 22 includes a calibration module 80 that includes calibration data that can be set to various values. The calibration data may be provided to a scaling module 81, which may scale the amplitude of the envelope signal using the calibration data before providing the scaled amplitude signal to the shaping table module 82. For example, as shown in fig. 6, the multiplier 87 may be configured to multiply the calibration data from the calibration module 80 by the Power Control Level (PCL) from the power control module 85 and by the envelope signal to generate a scaled envelope signal. However, the scaling module 81 may scale the envelope signal in any suitable manner using the calibration data.

Calibration module 80 may calibrate envelope tracker 22 using the calibration data to correct for envelope magnitude misalignment using a multi-step calibration process. For example, calibration module 80 may begin by setting the calibration data to a value that scales the value of the envelope signal value by a relatively large amount, thereby directing shaping table module 82 to supply power to voltage V_CCSet to a relatively high value, such as the maximum power supply voltage of the power amplifier. The relatively high voltage of the power supply may correspond to substantially no gain compression of power amplifier 32.

When the power amplifier system is configured for substantially no gain compression as described above, the power detector 86 may be configured to measure the output power of the power amplifier 32. Thereafter, the calibration module 80 may change the state or value of the calibration data, thereby directing the target supply voltage generated by the shaping table module 82 downward. For example, the scaling module 81 may use the calibration data to reduce the scaling factor, thereby causing the shaping table module 82 to lower the target power supply voltage.

For each reduction in the power supply voltage, the power detector 86 may measure the output power and provide the output power measurement to the power control module 85. Using this information, the calibration module 80, or any other suitable module, may determine when the values of the calibration data correspond to a gain compression approximately equal to the shaping table used to generate the shaping table module 82. For example, when the shaping table of shaping table module 82 is generated at 2dB gain compression, calibration module 80 may determine when the output power measured by power detector 86 is about 2dB less than the output power measured when the power amplifier system is configured in a substantially no gain compression state.

Calibration data associated with power amplifier gain compression equal to the shaping table used to generate the shaping table module 82 may be stored in the power amplifier system, such as in the memory of the envelope tracker 22. The calibration data may be used to compensate for envelope magnitude misalignment of the power amplifier system.

The calibration scheme described above may be relatively low cost, take a relatively short amount of time, and may be used to account for envelope magnitude misalignments from multiple sources. Furthermore, using the power detector 86 for power measurement avoids the need to support calibration using external test equipment.

In some embodiments, the calibration module 80 may be used to perform factory level calibration of the envelope tracker 22 during manufacturing. However, in other embodiments, the calibration module 80 may calibrate the envelope tracker 22 periodically during real-time operation, thereby accounting for dynamic errors from temperature or other environmental factors and/or operating conditions that may dynamically vary envelope magnitude misalignment errors over time. The calibration may be performed during any suitable time window, such as certain times (time instant) when the power amplifier system is not transmitting a signal via the antenna 14.

Fig. 7 is a schematic block diagram of a power amplifier system 99 according to another embodiment. Power amplifier system 99 includes duplexer 12, transceiver 13, antenna 14, battery 21, envelope tracker 22, VGA31, power amplifier 32, and directional coupler 88.

The envelope tracker 22 is shown to include a scaling module 81, a shaping table module 82, a digital-to-analog converter 83 and a modulator 84. The power amplifier system of fig. 7 may be similar to the power amplifier system of fig. 6 described above. However, unlike the power amplifier system 98 shown in fig. 6, the power amplifier system 99 shown in fig. 7 includes a calibration module 90 and a multiplier 91 for controlling the gain of the VGA 31.

The calibration module 90 includes calibration data that can be set to various values. The calibration data may be used to select the gain of VGA31, thereby controlling the input power provided to power amplifier stage 32. As will be described below, the calibration module 32 may be used to correct for envelope magnitude misalignment of the envelope tracker.

Calibration module 90 may use the calibration data to calibrate envelope tracker 22 to correct for envelope magnitude misalignment using a multi-step calibration process. For example, the calibration module 90 may begin by setting the gain of the VGA31 to a maximum power control level, while the envelope tracker 22 may be configured to generate a power supply voltage that is nominal and consistent with the target power of the power amplifier.

When the power amplifier system is configured with the target power, calibration module 90 may change the state of the calibration data, thereby directing the gain of VGA31 upward, thereby increasing the input power of power amplifier 32.

For each increase in input power, the power detector 86 may measure the output power and provide the measurement to the power control module 85. Using this information, the calibration module 90 or any other suitable component of the power amplifier system may determine when the values of the calibration data correspond to a gain compression approximately equal to the gain compression used to generate the shaping table of the shaping table module 82. For example, when the gain of the power amplifier drops below a value associated with the target power due to an increase in the input power, the power amplifier system has exceeded the gain compression point of the power amplifier system.

Calibration data corresponding to when the power amplifier gain compression is approximately equal to the gain compression used to generate the shaping table may be stored in the power amplifier system, such as in the memory of the envelope tracker 22 or the transceiver 13. The calibration data may be used to compensate for envelope magnitude misalignment of the power amplifier system 99. To allow the power control module 85 to also be able to vary the gain of the VGA31, a multiplier 91 may be included so that both the calibration module 90 and the power control module 85 can control the gain of the VGA 31. However, in some embodiments, the multiplier 91 may be replaced with other components, such as an adder, or the multiplier 91 may be omitted.

Fig. 8 is a flow chart illustrating a method 100 of calibrating a power amplifier system according to one embodiment. It should be appreciated that the methods discussed herein may include more or fewer operations, and that the operations may be performed in any order as desired. The method 100 may be used to calibrate a power amplifier system 98 such as that shown in fig. 6.

The method 100 begins at block 102. In a next block 104, a supply voltage for the power amplifier is generated using an envelope tracker that includes a shaping table generated at a desired gain compression. Gain compression in a power amplifier may refer to a reduction in differential gain caused by overdriving the power amplifier beyond the linear region. Thus, the shaping table may be calibrated at a desired gain compression determined to be an acceptable level of gain compression for the design, and the envelope shaping table may map the envelope signal amplitude to a power supply voltage level corresponding to the desired gain compression. The shaping table may comprise shaping data relating the plurality of scaled envelope signal amplitudes to a plurality of target power supply voltage levels.

In a next occurring block 106, a supply voltage of the power amplifier is operated at a first voltage level associated with substantially no gain compression of the PA. For example, the power amplifier may be operated at a maximum power supply voltage, thereby providing maximum active space for the amplified signal and substantially no gain compression.

The method 100 of fig. 8 continues at block 108 where the output power of the power amplifier at the first voltage level is measured. For example, a power detector may be used to measure the output power. One of ordinary skill in the art will appreciate that measuring the output power may include measuring current, voltage, and/or other parameters associated with power calculations, and calculating power therefrom.

In a block 110 that ensues, the voltage level of the supply voltage may be reduced one or more times, and the output power may be measured at each voltage level. The voltage level may be lowered discontinuously and power measurements taken after each lowering. However, in some embodiments, the voltage level may be continuously reduced and measurements may be taken at discrete points or continuously. The power measurement may be made using a power detector or any other suitable component. In one embodiment, the supply voltage is reduced by changing calibration data in a calibration module of the power amplifier system.

The method 100 continues at block 112 where a second voltage level of the power supply is determined that corresponds to a gain compression approximately equal to the gain compression used to generate the envelope shaping table. For example, the voltage level may be decreased until the measured output power drops below the output power at the first supply level by an amount approximately equal to the gain compression of the envelope shaping table.

In a next occurring block 114, the envelope tracker is calibrated based on the determination. For example, calibration data corresponding to the state of the system at the second voltage level may be stored and used to calibrate the power amplifier system. The method ends at 116.

Fig. 9 is a flow chart illustrating a method of calibrating a power amplifier system according to another embodiment. It should be appreciated that the methods discussed herein may include more or fewer operations, and that the operations may be performed in any order as desired. The method 150 may be used to calibrate a power amplifier system 99 such as that shown in fig. 7.

The method 150 begins at block 152. In a next block 154, the supply voltage of the power amplifier is generated using an envelope tracker that includes a shaping table generated at a desired gain compression point. The shaping table may comprise shaping data relating a plurality of scaled envelope signal amplitudes to a plurality of desired supply voltage levels.

In a next occurring block 156, the supply voltage of the power amplifier is operated at a first voltage level and a first input power level associated with the target power. For example, the power amplifier may be operated at a supply voltage level lower than the maximum supply voltage, and at a relatively low input power consistent with the target power.

The method 150 of fig. 9 continues at block 158 where the output power of the power amplifier is measured at the first voltage level and the first input power level to determine the power gain. For example, a power detector may be used to measure the output power.

In a block 160 that ensues, the input power to the power amplifier is increased one or more times, and the output power may be measured at each voltage level. The input power may be increased in any suitable manner, such as by changing the gain of a variable gain amplifier configured to drive the input of the power amplifier.

The method 150 continues at block 162 where a second input power level of the power supply is determined that corresponds to a gain compression approximately equal to the gain compression used to generate the envelope shaping table. For example, the input power may be reduced until the gain begins to drop, thereby indicating that the gain compression has exceeded the gain compression used to determine the envelope shaping table.

In a next occurring block 164, the envelope tracker is calibrated based on the determination. For example, calibration data corresponding to a state of the system at the second input power level may be stored and used to calibrate the power amplifier system. The method 150 ends at 166.

Applications of

Some of the above described embodiments have provided examples in relation to mobile phones. However, the principles and advantages of the embodiments may be applied to any other system or apparatus having requirements for a power amplifier system.

Such a power amplifier system may be implemented in various electronic devices. Examples of the electronic device may include, but are not limited to, consumer electronics, components of consumer electronics, electronic test equipment, and the like. Examples of electronic devices may also include, but are not limited to, memory chips, memory modules, circuitry for optical networks or other communication networks, and disk drive circuitry. Consumer electronics products may include, but are not limited to, mobile phones, telephones, televisions, computer monitors, computers, handheld computers, Personal Digital Assistants (PDAs), microwave ovens, refrigerators, automobiles, stereos, cassette recorders or players, DVD players, CD players, VCRs, MP3 players, radios, cameras, digital cameras, portable memory chips, washing machines, dryers, washer/dryers, copiers, facsimile machines, scanners, multifunction peripherals, wristwatches, clocks, and the like. Further, the electronic device may include unfinished products.

Conclusion

Throughout the specification and claims, the words "comprise", "comprising" and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, unless the context clearly requires otherwise; i.e., in the sense of "including, but not limited to". The word "coupled," as used generally herein, refers to two or more elements that may be connected directly or through one or more intervening elements. Also, the word "connected," as used herein generally, refers to two or more elements that may be connected directly or through one or more intervening elements. Moreover, the words "herein," "above," "below," and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Words using the singular or plural number in the above detailed description may also include the plural or singular number, respectively, as the context permits. The word "or" in reference to a list of two or more items covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

Furthermore, conditional language such as, inter alia, "may," "might," "may," "for example," "such as," and the like, as used herein, are generally intended to convey that certain embodiments include, but other embodiments do not include, certain, elements and/or states unless specifically stated to the contrary, or otherwise understood in the context at the time of use. Thus, such conditional language is not generally intended to imply that features, elements, and/or states are in any way required for one or more embodiments or that the one or more embodiments necessarily include (with or without author input or prompting) logic for deciding whether such features, elements, and/or states are included or are to be performed in any particular embodiment.

The above detailed description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. For example, while processes or blocks are presented in a given order, alternative embodiments may perform flows having steps in a different order or employ systems having blocks in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these processes or blocks may be implemented in a variety of different ways. In addition, while processes or blocks are sometimes shown as being performed in series, these processes or blocks may be performed in parallel, or may be performed at different times.

The teachings of the invention provided herein may be applied to other systems, not necessarily the system described herein. The elements and acts of the various embodiments described above can be combined to provide further embodiments.

While specific embodiments of the invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms and modifications as would fall within the scope and spirit of the disclosure.

Claims (30)

1. A method of calibrating an envelope tracking system, the method comprising:

scaling an amplitude of the envelope signal based on a scaling factor to generate a scaled envelope signal, the scaling factor determined at least in part by calibration data of an envelope tracker;

generating a supply voltage for a power amplifier using the envelope tracker having an envelope shaping table generated at a desired gain compression of the power amplifier based at least in part on the scaled envelope signal;

operating a supply voltage of the power amplifier at a first voltage level associated with substantially no-gain compression of the power amplifier;

measuring an output power of the power amplifier at a first voltage level;

after measuring the output power of the power amplifier at the first voltage level, reducing the voltage level of the supply voltage one or more times and measuring the output power at each voltage level until the measured output power is reduced to less than the output power at the first supply level by an amount approximately equal to the desired gain compression;

determining a second voltage level of the power amplifier associated with gain compression approximately equal to the desired gain compression based on the measured output power at each voltage level; and

the envelope tracker is calibrated based on the determined second voltage level.

2. The method of claim 1, wherein the envelope shaping table contains shaping data relating a plurality of scaled envelope signal amplitudes to a plurality of supply voltage levels.

3. The method of claim 2, further comprising generating a supply voltage from the battery voltage using the shaped data and the scaled envelope signal.

4. The method of claim 3, wherein the shaped data is in a digital format, the method further comprising converting the shaped data to an analog format.

5. The method of claim 1, wherein reducing a voltage level of a supply voltage includes changing calibration data of an envelope tracker to reduce the supply voltage.

6. The method of claim 5, wherein calibrating the envelope tracker based on the determined second voltage level includes selecting a value of calibration data approximately equal to a value of calibration data corresponding to the second voltage level.

7. The method of claim 5, wherein scaling an amplitude of an envelope signal comprises multiplying an envelope signal by the scaling factor determined at least in part by calibration data.

8. The method of claim 7, wherein the scaling factor is further determined by a power control signal from the transceiver.

9. The method of claim 1, wherein measuring the output power of the power amplifier at the first voltage level includes measuring the output power using a directional coupler and a power detector electrically coupled to an output of the power amplifier.

10. The method of claim 1, wherein the first voltage level is approximately equal to a maximum supply voltage of the power amplifier.

11. The method of claim 1, wherein reducing the voltage level of the supply voltage one or more times comprises reducing the level in discrete steps.

12. The method of claim 1, wherein reducing the level of the supply voltage one or more times and measuring the output power at each voltage level includes continuously reducing the voltage level and measuring the output power at a plurality of discrete voltage levels.

13. A power amplifier system, comprising:

a power amplifier;

an envelope tracker configured to generate a supply voltage for the power amplifier, the envelope tracker comprising a shaping module having an envelope shaping table generated at a desired gain compression of the power amplifier, the envelope tracker further comprising a scaling module configured to scale an amplitude of the envelope signal based on a scaling factor and to provide the scaled envelope signal amplitude to the shaping module;

a directional coupler electrically connected to an output of the power amplifier;

a power detector electrically connected to the directional coupler and configured to measure an output power of the power amplifier using the directional coupler; and

a calibration module configured to provide calibration data to the scaling module to thereby vary the scaled envelope signal amplitude generated by the scaling module, the calibration data at least partially determining a scaling factor for the scaling module, the calibration module configured to begin by setting the calibration data to a first value corresponding to a voltage level of the supply voltage associated with substantially no gain compression and to reduce the voltage level of the supply voltage by varying the calibration data until the power detector indicates that the gain compression of the power amplifier is approximately equal to the desired gain compression.

14. The power amplifier system of claim 13 wherein the envelope shaping table contains shaping data relating a plurality of scaled envelope signal amplitudes to a plurality of supply voltage levels.

15. The power amplifier system of claim 14 further comprising a modulator configured to generate a supply voltage from a battery voltage using the shaping data.

16. The power amplifier system of claim 15 further comprising a digital-to-analog converter for converting the shaped data to analog data for use by the modulator.

17. The power amplifier system of claim 13, further comprising a power control module electrically connected to the power detector.

18. The power amplifier system of claim 17 wherein the scaling module is further configured to receive a power control signal from the power control module, the scaling module configured to vary the scaled envelope signal amplitude using the power control signal.

19. The power amplifier system of claim 18, wherein the scaling module is configured to multiply the calibration data by the power control signal to generate a scaling factor and to multiply the amplitude of the envelope signal by the scaling factor to generate a scaled envelope signal amplitude.

20. The power amplifier system of claim 13, wherein the first value of the calibration data corresponds to about a maximum supply voltage of the power amplifier.

21. The power amplifier system of claim 13, further comprising a duplexer having an input electrically connected to the output of the power amplifier and the directional coupler, and an output electrically connected to the antenna.

22. A method of calibrating a power amplifier system, the method comprising:

generating a supply voltage for a power amplifier using an envelope tracker having an envelope shaping table generated at a desired gain compression of the power amplifier;

operating a supply voltage of a power amplifier at a first voltage level and a first input power level associated with a target power of the power amplifier;

measuring an output power of the power amplifier at a first input power level to determine a power gain;

increasing the input power of the power amplifier one or more times after measuring the output power of the power amplifier at the first input power level, and measuring the output power at each input power level;

determining a second input power level corresponding to a gain compression of the power amplifier approximately equal to the desired gain compression based on the output power measured at each voltage level;

calibrating the power amplifier system based on the determined second input power level; and

the calibration data and a power control signal from the transceiver are used to change the gain of a variable gain amplifier configured to drive an input of the power amplifier.

23. The method of claim 22, wherein increasing the input power of the power amplifier one or more times comprises changing the calibration data to increase the gain of the variable gain amplifier one or more times.

24. The method of claim 23, wherein calibrating a power amplifier system based on the determined second input power level comprises selecting a value of calibration data approximately equal to a value of calibration data corresponding to the second input power level.

25. The method of claim 22, further comprising further controlling the gain of the variable gain amplifier using a power control signal from the transceiver.

26. The method of claim 25, further comprising controlling the gain of the variable gain amplifier by multiplying the calibration data by the power control signal.

27. The method of claim 22, wherein measuring the output power of the power amplifier at the first input power level to determine the power gain comprises measuring the output power using a directional coupler and a power detector electrically coupled to an output of the power amplifier.

28. A power amplifier system, comprising:

a power amplifier;

a variable gain amplifier configured to drive an input of the power amplifier;

an envelope tracker configured to generate a supply voltage for the power amplifier, the envelope tracker comprising an envelope shaping table generated at a desired gain compression of the power amplifier;

a directional coupler electrically connected to an output of the power amplifier;

a power detector electrically connected to the directional coupler and configured to measure an output power of the power amplifier using the directional coupler;

a calibration module configured to provide calibration data to the variable gain amplifier to control an input power of the power amplifier, the calibration module configured to begin by setting the calibration data to a first value corresponding to a voltage level of the supply voltage and the input power of the power amplifier associated with a target power of the power amplifier and to increase the input power of the power amplifier by changing the calibration data until the power detector indicates that a gain compression of the power amplifier is approximately equal to a desired gain compression; and

a power control module electrically connected to the power detector and configured to generate a power control signal for controlling a gain of the variable gain amplifier.

29. The power amplifier system of claim 28 wherein the power amplifier system comprises a multiplier for multiplying the calibration data by the power control signal to generate a gain control signal for controlling the gain of the variable gain amplifier.

30. The power amplifier system of claim 28 further comprising a duplexer having an input electrically connected to the output of the power amplifier and the directional coupler, and an output electrically connected to the antenna.