Envelope trackers providing compensation for power amplifier output load variation

• US 10,236,831 B2
• Filed: 05/02/2018
• Issued: 03/19/2019
• 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:
  US15/969,075
• Publication Number:
  US 20180331659A1
• Time in Patent Office: 321 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 a power amplifier that amplifies an RF signal, an output detector coupled to an output of the power amplifier and that generates an output detection signal, an input detector coupled to an input of the power amplifier and that generates an input detection signal, and an envelope tracker that generates a power amplifier supply voltage for the power amplifier based on an envelope of the RF signal. The envelope tracker compensates the power amplifier for output load variation based on the output detection signal and the input detection signal.

Claims

1. A radio frequency system comprising:

a power amplifier including an input configured to receive a radio frequency signal and an output configured to provide an amplified radio frequency signal, the power amplifier configured to receive power from a power amplifier supply voltage;

an output detector coupled to the output of the power amplifier and configured to generate an output detection signal;

an input detector coupled to the input of the power amplifier and configured to generate an input detection signal; and

an envelope tracker configured to generate the power amplifier supply voltage based on an envelope of the radio frequency signal, and to compensate the power amplifier for output load variation based on the output detection signal and the input detection signal.

2. The radio frequency system of claim 1 wherein the output detection signal indicates a voltage gain at the output of the power amplifier, the envelope tracker configured to provide compensation for output load variation based on comparing the voltage gain to a target gain.

3. The radio frequency system of claim 1 wherein the output detection signal indicates both a voltage gain and a forward gain at the output of the power amplifier, the envelope tracker configured to provide compensation for output load variation based on comparing the voltage gain to the forward gain.

4. The radio frequency system of claim 1 wherein the output detection signal indicates both a forward wave and a reverse wave at the output of the power amplifier.

5. The radio frequency system of claim 1 wherein the envelope tracker includes a load variation detector configured to generate a 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 5 wherein the envelope tracker is configured to adjust at least one of a voltage level of the power amplifier supply voltage or a gain of the power amplifier based on the load variation detection signal.

7. The radio frequency system of claim 5 wherein the envelope tracker includes an envelope modulator configured to generate the power amplifier supply voltage 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.

8. The radio frequency system of claim 7 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.

9. The radio frequency system of claim 1 further comprising a duplexing and switching circuit coupled to the output of the power amplifier, the output detector configured to provide output detection prior to the duplexing and switching circuit.

10. A mobile device comprising:

a transceiver configured to generate a radio frequency signal;

a front end system including a power amplifier configured to provide amplification to the radio frequency signal, an output detector configured to generate an output detection signal indicating an output signal condition of the power amplifier, and an input detector configured to generate an input detection signal indicating an input signal condition of the power amplifier; and

a power management system including an envelope tracker configured to generate a power amplifier supply voltage of the power amplifier based on an envelope of the radio frequency signal, the envelope tracker configured to compensate the power amplifier for output load variation based on the output detection signal and the input detection signal.

11. The mobile device of claim 10 further comprising an antenna configured to receive an amplified radio frequency signal from the power amplifier, the envelope tracker configured to compensate the power amplifier for output load variation arising from a voltage standing wave ratio condition of the antenna.

12. The mobile device of claim 10 wherein the output detection signal indicates a voltage gain of the power amplifier, the envelope tracker configured to provide compensation for output load variation based on comparing the voltage gain to a target gain.

13. The mobile device of claim 10 wherein the output detection signal indicates both a voltage gain and a forward gain of the power amplifier, the envelope tracker configured to provide compensation for output load variation based on comparing the voltage gain to the forward gain.

14. The mobile device of claim 10 wherein the envelope tracker includes a load variation detector configured to generate a 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.

15. The mobile device of claim 14 wherein the envelope tracker is configured to adjust at least one of a voltage level of the power amplifier supply voltage or a gain of the power amplifier based on the load variation detection signal.

16. The mobile device of claim 14 wherein the envelope tracker includes an envelope modulator configured to generate the power amplifier supply voltage 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.

17. The mobile device of claim 16 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.

18. A method of envelope tracking in a radio frequency system, the method comprising:

amplifying a radio frequency signal using a power amplifier;

generating an output detection signal indicating an output signal condition of the power amplifier using an output detector of the power amplifier;

generating an input detection signal indicating an input signal condition of the power amplifier using an input detector of the power amplifier;

generating a power amplifier supply voltage for 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 based on the output detection signal and the input detection signal using the envelope tracker.

19. The method of claim 18 further comprising compensating the power amplifier for output load variation arising from a voltage standing wave ratio condition of an antenna.

20. The method of claim 18 further comprising generating a 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, and providing compensation for output load variation based on the load variation detection signal.