Multiple polar amplifier architecture

• US 6,998,914 B2
• Filed: 11/21/2003
• Issued: 02/14/2006
• Est. Priority Date: 11/21/2003
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Robinson, Ian
• Primary Examiner(s): Nguyen, Khanh V.
• Application Number:
  US10/719,513
• Publication Number:
  US 20050110565A1
• Time in Patent Office: 816 Days
• Field of Search: 330/10, 330/124.R
• US Class Current: 330/124.00R
• 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 1/0222 by using a signal derived from the input signal
• CPC Class Codes: H03F 1/0277 Selecting one or more amplifiers from a plurality of amplifiers
• CPC Class Codes: H03F 2200/331 Sigma delta modulation being used in an amplifying circuit

Abstract

An amplifier system for amplifying an input signal comprises first and second polar amplifier assemblies and a mode selector. The first polar amplifier assembly is operative to amplify the input signal to produce an amplified output signal for the system when the system is in a first mode. The second polar amplifier assembly is operative to amplify the input signal to produce the amplified output signal for the system when the system is in a second mode. A mode selector selects a mode of operation from at least the first and second modes for the amplifier system according to at least one characteristic of the input signal relative to at least one threshold parameter.

Claims

1. An amplifier system that amplifies an input signal comprising:

a first polar amplifier assembly operative to amplify the input signal to produce an amplified output signal for the system when the system is in a first mode;

a second polar amplifier assembly operative to amplify the input signal to produce the amplified output signal for the system when the system is in a second mode;

a correction path that is operative to provide at least a substantial portion of the amplified output signal when the system is in a third mode; and

a mode selector that selects a mode of operation from at least the first, second, and third modes for the amplifier system according to at least one characteristic of the input signal relative to at least one threshold parameter.

2. The system of claim 1, the at least one characteristic of the input signal comprising the amplitude of the input signal envelope.

3. The system of claim 1, the first polar amplifier assembly being fabricated via a first fabrication technology having a first set of associated properties, and the second polar amplifier assembly being fabricated via a second fabrication technology having a second set of associated properties.

4. The system of claim 3, the first fabrication technology comprising one of Gallium Nitride (GaN) and Laterally Diffused Metal Oxide Semiconductors (LDMOS) and the second fabrication technology comprising one of Gallium Arsenide (GaAs), Indium Phosphide (InP), and Complementary Metal Oxide Semiconductors (CMOS).

5. The system of claim 1, the amplifier system comprising N polar amplifier assemblies, where N is an integer greater than two, each of the N polar amplifier assemblies having associated modes that can be selected by the mode selector according to at least one characteristic of the input signal.

6. The system of claim 1, the input signal being a phase and/or amplitude modulated signal and the at least one threshold parameters representing respective envelope amplitude levels associated with the input signal, such that the first mode is selected when the input signal envelope amplitude level is greater than a first threshold parameter, the second mode is selected when the input signal envelope amplitude level falls between the first threshold parameter and a second threshold parameter, and the third mode is selected when the input signal envelope amplitude level falls below the second threshold parameter.

7. The system of claim 1, the mode selector providing a digital representation of a reference signal corresponding to a desired amplified output signal to a first summer through a digital-to-analog converter (DAC), the first summer receiving a portion of an output of the amplifier system through a coupler and providing a cancellation signal to a cancellation amplifier, the amplified cancellation signal being inverted and combined with a delayed version of the amplified output signal through a second summer.

8. The system of claim 7, the cancellation amplifier being a linear amplifier.

9. The system of claim 1, the first and second polar amplifier assemblies comprising respective first and second power amplifiers, each of the first and second power amplifiers having an associated input terminal and an associated supply terminal.

10. The system of claim 1, the first and second power amplifiers being non-linear class type amplifiers.

11. The system of claim 9, the mode selector providing a phase modulated digital input signal to the input terminal of the first power amplifier through a first DAC, and a amplitude modulated digital supply signal to the supply terminal of the first power amplifier through a second DAC and a first modulation amplifier when the system is operating in the first mode, and providing the phase modulated digital input signal to the input terminal of the second power amplifier through a third DAC, and the amplitude modulated digital supply signal to the supply terminal of the second power amplifier through a fourth DAC and a second modulation amplifier when the system is operating in the second mode.

12. The system of claim 1, at least one of the first, second, third, and fourth DACs being delta-sigma DACs, such that the at least one of the phase modulated digital input signal and the amplitude modulated digital supply signal are converted into the analog domain directly at a desired radio transmission frequency.

13. The system of claim 1, the first modulation amplifier and the second modulation amplifier each being one of a Class-S type and a Class-G type modulator.

14. The system of claim 1, the mode selector providing a reference signal corresponding to a desired output signal of the amplifier system to a digital cross-cancellation assembly, the reference signal being combined with a portion of the amplified output signal to determine a cancellation signal, the cancellation signal being amplified, inverted and combined with a delayed version of the amplified output signal to generate a final output signal.

15. The system of claim 14, the digital cross-cancellation assembly being associated with the third mode, the amplified inverted cancellation signal providing at least a substantial portion of the amplified output signal while the third mode of operation is selected, and the amplified inverted cancellation signal mitigating signal distortion and out-of-band (OOB) emissions associated with the amplified output signal while one of the first and second modes of operation is selected.

16. The system of claim 15, the input signal being a phase and/or amplitude modulated signal and the at least one threshold parameters representing respective envelope amplitude levels associated with the input signal, such that the first mode is selected when the input signal envelope amplitude level is greater than a first threshold parameter, the second mode is selected when the input signal envelope amplitude level falls between the first threshold parameter and a second threshold parameter, and the third mode is selected when the input signal envelope amplitude level falls below the second threshold parameter.

17. A transmitter comprising the amplifier system of claim 1.

18. A base station comprising the transmitter of claim 17.

19. An amplifier system comprising:

a plurality of power amplifiers, each operative to amplify an input signal to provide an amplified output signal;

respective input paths coupled to respective input terminals of the plurality of power amplifiers;

respective supply paths coupled to respective supply terminals of the plurality of power amplifiers; and

a mode selector that selects one of the plurality of power amplifiers to operate as a polar amplifier based on a characteristic of the input signal relative to at least one threshold parameter and transmits one of a phase modulated component of the input signal, a constant amplitude signal and no signal to respective input terminals of at least one non-selected power amplifier from the plurality of power amplifiers and a substantially constant amplitude signal to the respective supply terminals of the at least one non-selected power amplifier.

20. The system of claim 19, further comprising an output arbitrator that produces a unified output signal from respective outputs of the plurality of power amplifiers.

21. The system of claim 20, the output arbitrator comprising at least one summer that sums the outputs of the plurality of power amplifiers.

22. The system of claim 19, the mode selector transmitting a phase modulated signal component of the input signal to the input terminal of the selected power amplifier and an amplitude modulated signal component of the input signal to the supply terminal of the selected power amplifier.

23. The system of claim 19, each of the plurality of power amplifiers being fabricated via an associated fabrication technique, the at least one threshold parameter being selected according to properties of the associated fabrication techniques.

24. A method of amplifying an input signal, the method comprising:

selecting between a first mode of operation, associated with a first polar amplifier, and a second mode of operation associated with a second polar amplifier, wherein the second mode of operation is selected when the amplitude of the input signal falls within an amplitude range that includes a distortion range associated with the second polar amplifier, the distortion range including a zero crossing point of the signal;

amplifying the input signal via the first polar amplifier in the first mode of operation and via the second polar amplifier in the second mode of operation while continuously switching between the plurality of modes of operation to provide an amplified output signal.

25. The method of claim 24, further comprising performing a signal correction on the amplified output signal, the signal correction comprising generating a separate reference signal corresponding to a desired output signal, the reference signal being combined with a portion of the amplified output signal to determine a cancellation signal, the cancellation signal being amplified, inverted and combined with a delayed version of the amplified output signal to generate a final output signal.

26. The method of claim 25, the signal correction mitigating distortion and out-of-band (OOB) emissions during the first and second modes of operation and providing at least a substantial portion of the amplified output signal when the amplitude of the input signal falls within the distortion range of the second amplifier.

27. An amplifier system comprising:

a plurality of power amplifiers, each operative to amplify an input signal to provide an amplified output signal;

respective input paths coupled to respective input terminals of the plurality of power amplifiers;

respective supply paths coupled to respective supply terminals of the plurality of power amplifiers;

a mode selector that selects one of the plurality of power amplifiers to operate as

a polar amplifier based on a characteristic of the input signal relative to at least one threshold parameter;

an output arbitrator that produces a unified output signal from respective outputs of the plurality of power amplifiers; and

a correction path that mitigates signal distortion and out-of-band (OOB) emissions associated with the unified output signal.

28. The system of claim 27, the correction path comprising:

a digital-to-analog converter (DAC) having an input coupled to the mode selector;

a first summer having a first input coupled to an output of the DAC and a second input coupled to an output of the output arbitrator through a coupler;

a cancellation amplifier having an input coupled to an output of the first summer and an output coupled to a second summer, wherein the DAC receives a digital representation of a reference signal corresponding to a desired amplified output signal that is converted into an analog reference signal and combined with a portion of the unified output signal through the first summer to provide a cancellation signal that is amplified by the cancellation amplifier, and the amplified cancellation signal is inverted and combined with a delayed version of the unified output signal through the second summer.