Method and apparatus for operating a radio-frequency power amplifier as a variable-class linear amplifier

• US 6,043,707 A
• Filed: 01/07/1999
• Issued: 03/28/2000
• Est. Priority Date: 01/07/1999
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Budnik, Brian Joseph
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Choe, Henry
• Application Number:
  US09/226,680
• Time in Patent Office: 446 Days
• Field of Search: 330/10, 330/107, 330/149, 330/136, 330/297, 375/296, 375/297
• US Class Current: 330/10
• CPC Class Codes: H03C 5/00 Amplitude modulation and angle modulation produced simultaneously or at will by the same modulating signal H03C7/00 takes precedence
• CPC Class Codes: H03F 1/02 Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
• CPC Class Codes: H03F 1/0222 by using a signal derived from the input signal
• 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 1/0261 with control of the polarisation voltage or current, e.g. gliding Class A
• CPC Class Codes: H03F 1/304 and using digital means
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 1/3282 Acting on the phase and the amplitude of 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 2200/504 the supply voltage or current being continuously controlled by a controlling signal, e.g. the controlling signal of a transistor implemented as variable resistor in a supply path for, an IC-block showed amplifier
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 2001/045 with means for improving efficiency

Abstract

A variable-class linear amplifier (600, 800, 900) applies a supply type of envelope modulation to an RF power amplifier operating in or near compression at highest envelope amplitudes, and transitions gradually to an envelope tracking type of operation at intermediate envelope amplitudes. The amplifier further transitions gradually to a linear class of operation with a constant supply voltage (508) at lowest envelope amplitudes.

Claims

1. A method of operating a radio-frequency (RF) power amplifier as a variable-class linear amplifier, the method comprising the steps of:

applying an envelope supply type of modulation at highest envelope amplitudes, to develop an output signal;

transitioning gradually to an envelope tracking type of operation at intermediate envelope amplitudes; and

further transitioning gradually to a linear class of operation with a constant supply voltage at lowest envelope amplitudes.

2. The method of claim 1, further comprising the step of

continuously applying both feedback and predistortion linearity correction techniques.

3. The method of claim 1, further comprising the step of

employing feedback to correct both amplitude and phase errors.

4. The method of claim 1, further comprising the step of

predistorting at least one of an RF signal and a supply modulation signal in response to amplifier temperature information.

5. The method of claim 1, further comprising the step of

providing feedback to both a forward RF path and a modulated supply path.

6. The method of claim 1, further comprising the step of

providing variable relative amounts of linearization correction feedback to a modulated supply path and to a forward RF path, dependent upon a degree to which the RF power amplifier is driven into compression by the forward RF path.

7. A variable-class linear radio-frequency (RF) power amplifier, comprising:

supply modulation means for applying an envelope supply type of modulation at highest envelope amplitudes, to develop an output signal;

envelope tracking means coupled to the supply modulation means for transitioning gradually to an envelope tracking type of operation at intermediate envelope amplitudes; and

linear operation means coupled to the supply modulation means for further transitioning gradually to a linear class of operation with a constant supply voltage at lowest envelope amplitudes.

8. The RF power amplifier of claim 7, further comprising

linearity correction means coupled to the supply modulation means for continuously applying both feedback and predistortion linearity correction techniques.

9. The RF power amplifier of claim 7, further comprising

feedback means coupled to the supply modulation means and coupled to a forward RF path for employing feedback to correct both amplitude and phase errors.

10. The RF power amplifier of claim 7, further comprising

predistortion means coupled to power amplifier temperature sensor means for predistorting at least one of an RF signal and a supply modulation signal in response to amplifier temperature information.

11. The RF power amplifier of claim 7, further comprising

dual feedback means for providing feedback to both a forward RF path and a modulated supply path.

12. The RF power amplifier of claim 7, further comprising

attenuator means for providing variable relative amounts of linearization correction feedback to a modulated supply path and to a forward RF path, dependent upon a degree to which the RF power amplifier is driven into compression by the forward RF path.

13. A method of operating a radio-frequency (RF) power amplifier as a variable-class linear amplifier, the method comprising the steps of:

coupling a composite RF signal to an input of the RF power amplifier, the signal having an envelope amplitude which varies with time;

forming a modulation waveform whose amplitude is substantially proportional to said envelope amplitude when said envelope amplitude is greater than a predetermined level, and whose amplitude transitions to a predetermined constant amplitude when said envelope amplitude is not greater than the predetermined level; and

driving a supply input of the RF power amplifier with the modulation waveform, thereby operating the RF power amplifier in a mode selected from a group of modes, including an envelope supply modulation mode, an envelope tracking mode, and a linear mode, the mode determined by the envelope amplitude.

14. The method of claim 13, further comprising the step of

continuously applying both feedback and predistortion linearity correction techniques.

15. The method of claim 13, further comprising the step of

employing feedback to correct both amplitude and phase errors.

16. The method of claim 13, further comprising the step of

predistorting at least one of an RF signal and a supply modulation signal in response to amplifier temperature information.

17. The method of claim 13, further comprising the step of

providing feedback to both a forward RF path and a modulated supply path.

18. The method of claim 13, further comprising the step of

providing variable relative amounts of linearization correction feedback to a modulated supply path and to a forward RF path, dependent upon a degree to which the RF power amplifier is driven into compression by the forward RF path.