Composite amplifier with optimized linearity and efficiency

• US 20040135630A1
• Filed: 10/27/2003
• Published: 07/15/2004
• Est. Priority Date: 05/18/2001
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Hellberg, Richard
• Granted Patent: US 6,897,721 B2
• Time in Patent Office: Days
• US Class Current: 330/149
• CPC Class Codes: H03F 1/0288 using a main and one or several auxiliary peaking amplifiers whereby the load is connected to the main amplifier using an impedance inverter, e.g. Doherty amplifiers
• CPC Class Codes: H03F 1/32 Modifications of amplifiers to reduce non-linear distortion by negative feedback H03F1/34
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0483 Transmitters with multiple parallel paths

Abstract

The invention relates to a composite amplifier (500) based on a main amplifier (510) and an auxiliary amplifier (520), and compensation for non-linear amplifier behavior by means of respective non-linear models (570, 575) of parasitic. In order to provide proper excitation of the non-linear models. a filter network (560) based on a linear model of the output network of the composite amplifier is provided. The linear filter network (550) basically determines ideal output node voltages, which are used as input to the respective non-linear models for generating appropriate compensation signals. The compensation signals are finally merged into the input signals of the respective sub-amplifiers (510, 520), thus effectively compensating for the effects of the non-linear parasitics.

Claims

1. A linearization method for a composite amplifier (500;

600;

700) having at least two sub-amplifiers (510, 520;

610, 620;

710, 720), said method comprising the steps of;

for at least one sub-amplifier;

determining a sub-amplifier output signal based on a linear model of the output network of the composite amplifier; and

emulating and compensating for, in the input signal to the sub-amplifier, a non-linear amplifier behavior based on a non-linear model of a sub-amplifier parasitic using the determined sub-amplifier output signal as input to the model.

2. The linearization method according to claim 1, wherein said emulating step includes the step of determining a compensation signal according to the non-linear model by applying the determined sub-amplifier output signal as input to the non-linear model;

and

said compensating step includes the step of merging the compensation signal into the sub-amplifier input signal to compensate for said non-linear amplifier behavior.

3. The linearization method according to claim 1, wherein said step of determining a sub-amplifier output signal is based at least partly on an interaction between two sub-amplifiers.

4. The linearization method according to claim 3, wherein said interaction is represented by a transimpedance between the two sub-amplifiers.

5. The linearization method according to claim 1, wherein said non-linear amplifier behavior is the compression behavior due to amplifier saturation, said compression behavior being modeled as a non-linear sub-amplifier parasitic.

6. The linearization method according to claim 1, wherein said steps of determining a sub-amplifier output signal and emulating and compensating for a non-linear amplifier behavior are performed for each sub-amplifier (510, 520;

610, 620;

710, 720).

7. The linearization method according to claim 1, wherein said method further comprises steps of emulating and compensating for, in the input signal to a main sub-amplifier (510;

610;

710), the non-linear output signal of an auxiliary sub-amplifier (520;

620;

720) based on a linear model of the output network of the composite amplifier.

8. The linearization method according to claim 1, wherein said method further comprises the steps of equalizing, for at least one of said sub-amplifiers, the amplifier frequency response.

9. A composite amplifier (500;

600;

700) having at least two sub-amplifiers (510, 520;

610, 620;

710, 720), wherein said composite amplifier comprises;

for at least one sub-amplifier;

means (560;

660;

782, H₁₁*G₂₁) for determining a sub-amplifier output signal based on a linear model of the output network of the composite amplifier;

means (570, 572, 575, 577;

670, 672, 675, 677;

770, 772, 775, 777) for emulating and compensating for, in the input signal to the sub-amplifier, a non-linear amplifier behavior based on a non-linear model of a sub-amplifier parasitic using the determined sub-amplifier output signal as input to the model.

10. The composite amplifier according to claim 9, wherein said emulating means includes means (570, 575;

670, 675;

770, 775) for determining a compensation 0signal according to the non-linear model in response to the determined sub-amplifier output signal as input to the non-linear model; and

said compensating means includes means (572, 577;

672, 677;

772, 777) for merging the compensation signal into the sub-amplifier input signal to compensate for said non-linear amplifier behavior.

11. The composite amplifier according to claim 9, wherein said means for determining a sub-amplifier output signal is based at least partly on an interaction between two sub-amplifiers.

12. The composite amplifier according to claim 11, wherein said interaction is represented by a transimpedance between the two sub-amplifiers.

13. The composite amplifier according to claim 9, wherein said composite amplifier further comprises means (690;

790) for emulating and compensating for, in the input signal to a main sub-amplifier (610;

710), the non-linear output signal of an auxiliary sub-amplifier (620;

720) based on a linear model of the output network of the composite amplifier.

14. The composite amplifier according to claim 9, wherein said composite amplifier further comprises, for at least one of said sub-amplifiers, means for equalizing the amplifier frequency response.

15. A transmitter (200) having a composite power amplifier (220;

500;

600;

700) based on at least two sub-amplifiers (510, 520;

610, 620;

710, 720), wherein said composite power amplifier comprises;

for at least one sub-amplifier;

means (560;

660;

782, H₁₁*G₂₁) for determining a sub-amplifier output signal based on a linear model of the output network of the composite amplifier;

means (570, 572, 575, 577;

670, 672, 675, 677;

770, 772, 775, 777) for emulating and compensating for, in the input signal to the sub-amplifier, a non-linear amplifier behavior based on a non-linear model of a sub-amplifier parasitic using the determined sub-amplifier output signal as input to the model.

16. The transmitter according to claim 15, wherein said emulating means includes means (570, 575;

670, 675;

770, 775) for determining a compensation signal according to the non-linear model in response to the determined sub-amplifier output signal as input to the non-linear model; and

said compensating means includes means (572, 577;

672, 677;

772, 777) for merging the compensation signal into the sub-amplifier input signal to compensate for said non-linear amplifier behavior.

17. The transmitter according to claim 15, wherein said means for determining, for at least one sub-amplifier, a sub-amplifier output signal is based at least partly on an interaction between two sub-amplifiers.

18. The transmitter according to claim 17, wherein said interaction is represented by a transimpedance between the two sub-amplifiers.

19. The transmitter according to claim 15, wherein said composite power amplifier further comprises means (690;

790) for emulating and compensating for, in the input signal to a main sub-amplifier (610;

710), the non-linear output signal of an auxiliary sub-amplifier (620;

720) based on a linear model of the output network of the composite amplifier.

20. The transmitter according to claim 15, wherein said composite power amplifier further comprises means for equalizing, for at least one of said sub-amplifiers, the amplifier frequency response.