Systems and methods providing loadline modulation of a power amplifier

• US 10,122,326 B2
• Filed: 03/29/2017
• Issued: 11/06/2018
• Est. Priority Date: 11/04/2016
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Cabanillas, Jose
• Primary Examiner(s): Choe, Henry
• Application Number:
  US15/472,504
• Publication Number:
  US 20180131333A1
• Time in Patent Office: 587 Days
• Field of Search: 330291, 330 85, 330305
• CPC Class Codes: H03F 1/0272 by using a signal derived from the output signal
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2200/171 A filter circuit coupled to the output of an amplifier
• 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 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/78 A comparator being used in a controlling circuit of an amplifier
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• CPC Class Codes: H03F 3/193 with field-effect devices H03F3/195 takes precedence
• CPC Class Codes: H03F 3/21 with semiconductor devices only H03F3/245 takes precedence
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H

Abstract

A circuit including: a power amplifier configured to provide amplified signals to a load; an impedance matching network disposed between the power amplifier and the load, the impedance matching network comprising an adjustable impedance unit; and a feedback loop comprising a rectifier, the rectifier being coupled with an output of the power amplifier, the feedback loop further comprising and impedance control circuit configured to receive a signal from the rectifier and to control the adjustable impedance unit in response to the signal from the rectifier.

Claims

1. A circuit comprising:

a power amplifier configured to provide amplified signals to a load;

an impedance matching network disposed between the power amplifier and the load, the impedance matching network comprising an adjustable impedance unit; and

a feedback loop comprising a rectifier, the rectifier being coupled with an output of the power amplifier, the feedback loop further comprising an impedance control circuit configured to receive a signal from the rectifier and to control the adjustable impedance unit in response to the signal from the rectifier, wherein the impedance control circuit comprises a weighting block configured to receive a rectified load voltage, and configured to generate a control signal for the adjustable impedance unit that is a function of the signal from the rectifier and the rectified load voltage.

2. The circuit of claim 1, wherein the impedance control circuit comprises a comparator, wherein the comparator is configured to receive a reference voltage corresponding to a voltage swing level at the output of the power amplifier and configured to receive the signal from the rectifier.

3. The circuit of claim 1, wherein the adjustable impedance unit comprises a variable capacitor coupled with the impedance control circuit.

4. The circuit of claim 3, wherein the variable capacitor comprises one of a diode having a voltage-dependent capacitance or a trans-cap.

5. The circuit of claim 1, wherein the power amplifier is configured to provide an amplified radio frequency (RF) signal to the load.

6. The circuit of claim 1, wherein the signal from the rectifier comprises one of a voltage signal or a current signal.

7. The circuit of claim 1, wherein the power amplifier comprises a metal oxide semiconductor (MOS) transistor, and wherein the impedance matching network is coupled with a drain of the MOS transistor.

8. The circuit of claim 1, wherein a voltage at the output of the power amplifier comprises a differential voltage.

9. The circuit of claim 1, wherein the load comprises an antenna.

10. A method performed at a radio frequency (RF) power amplifier (PA) system, the method comprising:

sampling a voltage swing at an output terminal of the PA, wherein the PA provides an amplified RF signal to a load;

generating a first control signal in response to the voltage swing;

applying the first control signal to a comparator to generate a second control signal, wherein the comparator receives a reference signal corresponding to a voltage swing threshold; and

adjusting an impedance of a matching network of the PA in response to the second control signal, wherein generating the first control signal comprises;

receiving a first rectified voltage from a first rectifier sampling the voltage swing;

receiving a second rectified voltage from a second rectifier sampling a voltage at the load; and

generating the first control signal as a function of the first rectified voltage and the second rectified voltage.

11. The method of claim 10, wherein generating a first control signal comprises:

rectifying a voltage signal from the output terminal of the PA.

12. The method of claim 10, wherein adjusting the impedance of the matching network comprises:

biasing a variable capacitor of the matching network in response to the second control signal.

13. The method of claim 10, wherein sampling a voltage swing comprises:

sampling a differential voltage at the output terminal of the PA.

14. The method of claim 10, further comprising:

receiving an RF signal at an input of the PA;

amplifying the RF signal by the PA; and

providing an amplified RF signal from the output terminal of the PA to the load.

15. A method performed in a radio frequency (RF) circuit having a power amplifier (PA), the method comprising:

providing an amplified RF signal from an output terminal of the PA to a load;

demodulating the amplified RF signal to generate an envelope signal;

processing the envelope signal to generate a control signal that is a function of the envelope signal; and

applying the control signal as a bias to an adjustable impedance element of a matching network, wherein the matching network is coupled between the output terminal of the PA and the load, further comprising applying a low pass filter to the control signal before applying the control signal as the bias to the adjustable impedance element.