Management of internal signal levels and control of the net gain for a linc amplifier

• US 20020047745A1
• Filed: 06/21/2001
• Published: 04/25/2002
• Est. Priority Date: 06/22/2000
• Status: Active Grant

• Current Assignee: Andrew LLC (CommScope Holding Company, Inc.), Nakabohtec Corrosion Protecting Co., Ltd., Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Andrew Amplifiers Inc. (CommScope Holding Company, Inc.)
• Inventors: Kolanek, James C.
• Granted Patent: US 6,633,200 B2
• Time in Patent Office: Days
• US Class Current: 330/149
• CPC Class Codes: H03F 1/0294 using vector summing of two or more constant amplitude phase-modulated signals
• CPC Class Codes: H03F 1/3223 using feed-forward H03F1/3211 takes precedence
• CPC Class Codes: H03F 2200/331 Sigma delta modulation being used in an amplifying circuit

Abstract

An amplifier subsystem has a modulator to generate a pair of constant amplitude phase-modulated components which are in response to an input signal, a pair of channels that include a pair of power amplifiers to amplify the components, and a combiner to combine the amplified components. A number of variable gain elements are coupled into some of a number of signal paths of the amplifier subsystem. A controller is to receive feedback from the amplifier subsystem and in response maintains signal levels of some of the signal paths within predefined ranges and controls a net gain of the linear amplifier, by adjusting the variable gain elements.

Claims

1. A linear amplifier comprising:

an amplifier subsystem having a modulator to generate a pair of constant- amplitude phase-modulated components in response to an input signal, a pair of channels which include a pair of power amplifiers coupled to amplify the components, respectively, a combiner coupled to combine the amplified components, and a plurality of variable gain elements coupled into some of a plurality of signal paths of the amplifier subsystem; and

a controller coupled to receive feedback from the amplifier subsystem and in response (1) maintain signal levels of some of the plurality of signal paths in predefined ranges and (2) control a net gain of the linear amplifier, by adjusting the plurality of variable gain elements.

2. The linear amplifier of claim 1 wherein the amplifier subsystem further comprises an equalizer coupled in a signal path between the modulator and the power amplifiers to make amplitude and phase corrections in one or both of the components, and the controller is further coupled to control the equalizer so that variation in frequency response between the pair of channels is reduced, the controller to further control a net gain of the equalizer, digital filter coefficients of the equalizer, and signal levels within the equalizer to maintain the net gain of the linear amplifier in a predefined range and simultaneously reduce the likelihood of overflows in the equalizer.

3. The linear amplifier of claim 1 wherein the amplifier subsystem further comprises a first A/D converter coupled to digitize the input signal in a signal path to the modulator and a second AID converter coupled to digitize a feedback signal in a signal path between an output of the combiner and the controller, and wherein the plurality of variable gain elements include a first analog variable gain element coupled to adjust a signal level into the first A/D converter and a second analog variable gain element coupled to adjust a signal level into the second A/D converter.

4. The linear amplifier of claim 3 wherein the plurality of variable gain elements further include third and fourth analog variable gain elements coupled to adjust the corrected components, respectively, prior to amplification.

5. The linear amplifier of claim 3 wherein the amplifier further comprises a down converter coupled to translate the input signal into a lower frequency range prior to being digitized, and an up converter coupled to translate the corrected components into an RF range prior to amplification.

6. The linear amplifier of claim 3 wherein some of the plurality of gain elements provide coarse, discretely variable gain and others provide fine, discretely variable gain, the controller further includes a converter to translate gain change commands into commands to the coarse and fine variable gain elements.

7. The linear amplifier of claim 6 wherein the fine, discretely variable gain elements are digitally implemented.

8. A method for operating a LINC amplifier, comprising:

generating a pair of constant-amplitude phase-modulated components in response to an input signal;

separately amplifying said components to a relatively high power level;

combining said amplified components; and

generating commands that cause gain changes in a plurality of signal paths of the LINC amplifier, in response to receiving feedback concerning said amplified components, to (1) maintain signal levels of some of the plurality of signal paths in predefined ranges and (2) control a net gain of the LINC amplifier.

9. The method of claim 8 wherein the feedback concerns a combined form of said amplified components.

10. The method of claim 8 further comprising making amplitude and phase corrections to one or both of said components so that variation in frequency response between the pair of channels is reduced as part of an equalization process, controlling a net gain of the equalization process, controlling digital filtering coefficients used in the equalization process, and controlling signal levels within the equalization process to maintain the net gain of the linear amplifier in a predefined range and simultaneously reduce the likelihood of overflows in the equalization process.

11. The method of claim 8 further comprising:

digitizing the input signal prior to generating said components; and

digitizing a feedback signal related to said amplified components, and wherein said commands cause adjustments to analog levels of the input signal and the feedback signal prior to digitization.

12. The method of claim 10 further comprising:

translating the input signal into a lower frequency range prior to digitization; and

translating the corrected components into an RF range prior to amplification.

13. The method of claim 11 wherein the commands cause adjustments in the corrected components prior to amplification.

14. The method of claim 11 wherein some of the plurality of gain elements are to provide coarse, discretely variable gain and others are to provide fine, discretely variable gain, the controller further includes a converter to translate gain change commands into commands to the coarse and fine variable gain elements.

16. The article of manufacture of claim 15 wherein the medium includes further instructions that, when executed by the processor, provide further commands that can control an equalizer to make amplitude and phase corrections in one or both of the components so that variation in frequency response between a pair of channels of the LINC amplifier is reduced, and further instructions that control a net gain of the equalizer, digital filter coefficients of the equalizer, and signal levels within the equalizer to maintain the net gain of the linear amplifier in a predefined range and simultaneously reduce the likelihood of overflows in the equalizer.

17. The article of manufacture of claim 15 wherein the medium includes further instructions that, when executed by the processor, provide further commands that can control adjustments to analog levels of the input signal and a feedback signal prior to the signals being digitized.

18. The article of manufacture of claim 17 wherein the medium includes further instructions that, when executed by the process, provide further commands that can control adjustments to analog levels of the components.

20. The amplifier of claim 19 further comprising:

a down converter coupled to translate the input signal into a lower frequency range prior to being digitized; and

an up converter coupled to translate the corrected components into an RF range prior to being amplified.

21. The amplifier of claim 19 wherein the control parameters are to further control third and fourth analog variable gain elements coupled to adjust the corrected components, respectively, prior to amplification.

22. The amplifier of claim 19 wherein the controller is to further control a net gain of the equalizer, digital filter coefficients of the equalizer, and signal levels within the equalizer to maintain the net gain of the linear amplifier in a predefined range and simultaneously reduce the likelihood of overflows in the equalizer.

15. An article of manufacture having a machine-readable medium with instructions stored therein that, when executed by a processor, provide commands that can cause gain changes in a plurality of signal paths of a LINC amplifier, in response to feedback concerning a plurality of amplified constant-amplitude phase-modulated components which are in response to an input signal to the LINC amplifer, to (1) maintain signal levels of some of the plurality of signal paths in predefined ranges and (2) control a net gain of the LINC amplifier.

19. A linear amplifier comprising:

a first A/D converter to digitize an input signal;

a modulator coupled to an output of the first A/D converter to generate a pair of constant amplitude phase modulated components in response to the input signal;

a pair of channels including an equalizer coupled to provide amplitude and phase corrections to one or both of the components, a D/A converter coupled to convert the corrected components into analog form, and a pair of phase-preserving power amplifiers coupled to amplify the corrected components, respectively;

a combiner coupled to combine the amplified components; and

a controller coupled to receive feedback from at least one of the pair of channels and the combiner, and in response control the equalizer so that variation in frequency response between the channels is reduced, wherein the controller is to further represent the influence of a plurality of control parameters upon a plurality of performance parameters in the amplifier, determine a plurality of current values of the performance parameters, and determine a plurality of values of the control parameters that allow the amplifier to meet a plurality of target values for the performance parameters, the control parameters are to control (1) a first analog variable gain element coupled to adjust an input signal level of the first A/D converter, and (2) a second analog variable gain element coupled to adjust an input signal level of a second A/D converter that is in a feedback path from an output of the combiner, and the performance parameters represent net amplifier gain and input signal level to the first A/D converter.