Envelope trackers providing compensation for power amplifier output load variation

• US 10,651,802 B2
• Filed: 02/01/2019
• Issued: 05/12/2020
• Est. Priority Date: 05/12/2017
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Khesbak, Sabah, Drogi, Serge Francois
• Primary Examiner(s): Tran, Pablo N
• Application Number:
  US16/265,097
• Publication Number:
  US 20190165736A1
• Time in Patent Office: 466 Days
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03F 1/0233 by using a signal derived from the output signal, e.g. bootstrapping the voltage supply
• CPC Class Codes: H03F 1/0255 by using a signal derived from the output signal
• CPC Class Codes: H03F 1/0266 by using a signal derived from the input signal
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2200/207 A hybrid coupler being used as power measuring circuit at the output of an amplifier circuit
• CPC Class Codes: H03F 2200/336 A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit
• CPC Class Codes: H03F 2200/36 the amplifier comprising means for increasing the bandwidth
• CPC Class Codes: H03F 2200/387 A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
• CPC Class Codes: H03F 2200/411 the output amplifying stage of an amplifier comprising two power stages
• CPC Class Codes: H03F 2200/417 A switch coupled in the output circuit of an amplifier being controlled by a circuit
• CPC Class Codes: H03F 2200/432 Two or more amplifiers of different type are coupled in parallel at the input or output, e.g. a class D and a linear amplifier, a class B and a class A amplifier
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/471 the voltage being sensed
• CPC Class Codes: H03F 2203/7215 the gated amplifier being switched on or off by a switch at the input of the amplifier
• CPC Class Codes: H03F 2203/7221 the gated amplifier being switched on or off by a switch at the output of the amplifier
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/21 with semiconductor devices only H03F3/245 takes precedence
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H03G 2201/307 being radio frequency signal
• CPC Class Codes: H03G 3/3042 : in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H04B 1/0475 : with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 2001/0408 : with power amplifiers
• CPC Class Codes: H04B 2001/045 : with means for improving efficiency

Abstract

Envelope trackers providing compensation for power amplifier output load variation are provided herein. In certain configurations, a radio frequency (RF) system includes an antenna, a power amplifier that receives a radio frequency signal and outputs an amplified radio frequency signal to the antenna, a plurality of detectors coupled to the power amplifier and operable to generate a plurality of detection signals, and an envelope tracker that controls a supply voltage of the power amplifier based on an envelope of the radio frequency signal. The envelope tracker processes the plurality of detection signals to generate a load variation detection signal indicating a change in an output load of the power amplifier arising from a change in a voltage standing wave ratio (VSWR) of the antenna. Additionally, the envelope tracker adjusts a gain of the power amplifier based on the load variation detection signal.

Claims

1. A radio frequency system comprising:

an antenna;

a power amplifier including an input configured to receive a radio frequency signal and an output configured to provide an amplified radio frequency signal to the antenna;

a plurality of detectors coupled to the power amplifier and configured to generate a plurality of detection signals; and

an envelope tracker configured to control a supply voltage of the power amplifier based on an envelope of the radio frequency signal, and to process the plurality of detection signals to generate a load variation detection signal indicating a change in an output load of the power amplifier arising from a change in a voltage standing wave ratio of the antenna, the envelope tracker further configured to adjust a gain of the power amplifier based on the load variation detection signal.

2. The radio frequency system of claim 1 wherein the envelope tracker is further configured to adjust a voltage level of the supply voltage of the power amplifier based on the load variation detection signal.

3. The radio frequency system of claim 1 wherein the envelope tracker includes an envelope modulator configured to control the supply voltage of the power amplifier based on a shaped envelope signal, and an envelope adjustment circuit configured to generate the shaped envelope signal based on shaping the envelope of the radio frequency signal.

4. The radio frequency system of claim 3 wherein the envelope adjustment circuit includes a shaping table, the envelope adjustment circuit configured to select a gain adjustment value of the shaping table based on the load variation detection signal.

5. The radio frequency system of claim 1 wherein the plurality of detection signals includes an input detection signal and an output detection signal, the envelope tracker further configured to generate the load variation detection signal based on compensating an output load variation indicated by the output detection signal by a nominal output load variation indicated by the input detection signal.

6. The radio frequency system of claim 1 wherein the plurality of detectors include an input voltage detector coupled to the input of the power amplifier, and an output voltage detector coupled to the output of the power amplifier.

7. The radio frequency system of claim 6 wherein the plurality of detectors further include a directional coupler coupled to the output of the power amplifier.

8. The radio frequency system of claim 1 wherein the plurality of detectors include an input voltage detector coupled to the input of the power amplifier, and a directional coupler coupled to the output of the power amplifier.

9. A method of envelope tracking in a mobile device, the method comprising:

amplifying a radio frequency signal using a power amplifier to generate an amplified radio frequency signal for an antenna;

generating a plurality of detection signals using a plurality of detectors coupled to the power amplifier;

controlling a supply voltage of the power amplifier based on an envelope of the radio frequency signal using an envelope tracker; and

compensating the power amplifier for output load variation using the envelope tracker, including processing the plurality of detection signals to generate a load variation detection signal indicating a change in an output load of the power amplifier arising from a change in a voltage standing wave ratio of the antenna, and adjusting a gain of the power amplifier based on the load variation detection signal.

10. The method of claim 9 wherein compensating the power amplifier for output load variation using the envelope tracker further includes adjusting a voltage level of the supply voltage of the power amplifier based on the load variation detection signal.

11. The method of claim 9 wherein compensating the power amplifier for output load variation using the envelope tracker further includes selecting a gain adjustment value of a shaping table based on the load variation detection signal.

12. The method of claim 9 wherein the plurality of detection signals includes an input detection signal and an output detection signal, the method further comprising generating the load variation detection signal based on compensating an output load variation indicated by the output detection signal by a nominal output load variation indicated by the input detection signal.

13. A mobile device comprising:

a front end system including a power amplifier configured to amplify a radio frequency signal to generate an amplified radio frequency signal, and a plurality of detectors coupled to the power amplifier and configured to generate a plurality of detection signals;

an antenna configured to transmit the amplified radio frequency signal; and

a power management system including an envelope tracker configured to control a supply voltage of the power amplifier based on an envelope of the radio frequency signal, and to process the plurality of detection signals to generate a load variation detection signal indicating a change in an output load of the power amplifier arising from a change in a voltage standing wave ratio of the antenna, the envelope tracker further configured to adjust a gain of the power amplifier based on the load variation detection signal.

14. The mobile device of claim 13 further comprising a transceiver configured to generate the radio frequency signal.

15. The mobile device of claim 13 wherein the envelope tracker is further configured to adjust a voltage level of the supply voltage of the power amplifier based on the load variation detection signal.

16. The mobile device of claim 13 wherein the envelope tracker includes a shaping table, the envelope tracker further configured to select a gain adjustment value of the shaping table based on the load variation detection signal.

17. The mobile device of claim 13 wherein the plurality of detection signals includes an input detection signal and an output detection signal, the envelope tracker further configured to generate the load variation detection signal based on compensating an output load variation indicated by the output detection signal by a nominal output load variation indicated by the input detection signal.

18. The mobile device of claim 13 wherein the plurality of detectors include an input voltage detector coupled to an input of the power amplifier, and an output voltage detector coupled to an output of the power amplifier.

19. The mobile device of claim 18 wherein the plurality of detectors further include a directional coupler coupled to the output of the power amplifier.

20. The mobile device of claim 13 wherein the plurality of detectors include an input voltage detector coupled to an input of the power amplifier, and a directional coupler coupled to an output of the power amplifier.