Amplifier

• US 20030112068A1
• Filed: 10/21/2002
• Published: 06/19/2003
• Est. Priority Date: 02/24/2000
• Status: Active Grant

• Current Assignee: Andrew LLC (CommScope Holding Company, Inc.)
• Original Assignee: Andrew Corporation (CommScope Holding Company, Inc.)
• Inventors: Kenington, Peter
• Granted Patent: US 6,847,259 B2
• Time in Patent Office: Days
• US Class Current: 330/136
• CPC Class Codes: H03F 1/0261 with control of the polarisation voltage or current, e.g. gliding Class A
• CPC Class Codes: H03F 1/3282 Acting on the phase and the amplitude of the input signal

Abstract

A signal to be amplified is provided in polar format comprising an amplitude component (210) and a phase component (212). The amplitude component (210) is used to bias the phase component (212). The gain of amplifier (220) depends upon the bias of the signal that it receives. Therefore, the bias given to the phase component (212) provides the envelope characteristics of the output signal (224) of amplifier (220). Both (or either) of the amplitude component (210) and the phase component (212) may be predistorted (226, 310) to eliminate distortion appearing in the output signal (224).

Claims

1. Apparatus for amplifying an input signal to produce an output signal, comprising means for providing the input signal in polar format comprising an amplitude component and a phase component, biasing means for deriving a bias signal from the amplitude component, means for combining the bias signal with the phase component to produce a biased phase component signal, and an amplifying means whose gain depends upon the bias provided to the signal it amplifies, wherein the amplifying means is supplied with the biased phase component signal to produce the output signal.

2. Apparatus according to claim 1, further comprising a linearising scheme for counteracting distortion in the output signal.

3. Apparatus according to claim 2, wherein the linearising scheme comprises means for subtracting modulation information obtained from the output signal from modulation information that is used to create the phase and amplitude components.

4. Apparatus according to claim 3, wherein the means for subtracting is arranged to subtract amplitude information obtained from the output signal from amplitude modulation information that is used to create the amplitude component.

5. Apparatus according to claim 3 or 4, wherein the means for subtracting is arranged to subtract phase information obtained from the output signal from phase modulation information that is used to create the phase component.

6. Apparatus according to claim 2, wherein the linearising scheme comprises a predistortion scheme for predistorting the input signal.

7. Apparatus according to claim 6, wherein the predistortion scheme comprises amplitude predistorting means for predistorting the amplitude component of the input signal.

8. Apparatus according to claim 6 or 7, wherein the predistortion scheme comprises phase predistorting means for predistorting the phase component of the input signal.

9. Apparatus according to any one of claims 6 to 8, wherein the predistortion scheme operates on at least one of the components of the input signal in the digital domain.

10. Apparatus according to any one of claims 6 to 9, wherein the predistortion scheme monitors residual distortion in the output signal and adapts the predistortion of the input signal to reduce the residual distortion.

11. Apparatus according to any preceding claim, wherein the input signal is provided as a modulated carrier signal, and the means for providing the input signal in polar format comprises means for limiting the modulated carrier signal to produce the phase component.

12. Apparatus according to any preceding claim, wherein the input signal is provided as a modulated carrier signal, and the means for providing the input signal in polar format comprises means for detecting the envelope of the modulated carrier signal to produce the amplitude component.

13. Apparatus according to any one of claims 1 to 10, wherein the input signal is provided as a quadrature signal and the means for providing the input signal in polar format comprises means for converting the input signal from quadrature to polar format.

14. Apparatus according to any one of claims 1 to 10, wherein the input signal is provided as a channel of amplitude modulation information and a channel of phase modulation information and the means for providing the input signal in polar format is arranged to derive the amplitude and phase components from the amplitude and phase modulation information channels, respectively.

15. Apparatus according to any preceding claim, wherein the biaising means is arranged to amplify envelope information from the amplitude component to derive the bias signal.

16. A method of amplifying an input signal to produce an output signal, comprising providing the input signal in polar format comprising an amplitude component and a phase component, deriving a bias signal from the amplitude component, combining the bias signal with the phase component to produce a biased phase component signal and amplifying the biased phase component signal to produce the output signal using an amplifier whose gain depends upon the bias provided to the signal which it amplifies.

17. A method according to claim 16, further comprising a linearising step for counteracting distortion in the output signal.

18. A method according to claim 17, wherein the linearising step comprises the step of subtracting modulation information obtained from the output signal from modulation information that is used to create the phase and amplitude components.

19. A method according to claim 18, wherein the subtracting step comprises subtracting amplitude information obtained from the output signal from amplitude modulation information that is used to create the amplitude component.

20. A method according to claim 18 or 19, wherein the subtracting step comprises subtracting phase information obtained from the output signal from phase modulation information that is used to create the phase component.

21. A method according to claim 17, wherein the linearising step comprises the step of predistorting the input signal.

22. A method according to claim 21, wherein the predistortion step comprises a step of predistorting the amplitude component of the input signal.

23. A method according to claim 21 or 22, wherein the predistortion step comprises the step of predistorting the phase component of the input signal.

24. A method according to any one of claims 21 to 23, wherein the predistortion step operates on at least one of the components of the input signal in the digital domain.

25. A method according to any one of claims 21 to 24, wherein the predistortion step comprises monitoring residual distortion in the output signal and adapting the predistortion of the input signal to reduce the residual distortion.

26. A method according to any one of claims 16 to 25, wherein the input signal is provided as a modulated carrier signal, and the step of providing the input signal in polar format comprises limiting the modulated carrier signal to produce the phase component.

27. A method according to any one of claims 16 to 26, wherein the input signal is provided as a modulated carrier signal, and the step of providing the input signal in polar format comprises detecting the envelope of the modulated carrier signal to produce the amplitude component.

28. A method according to any one of claims 16 to 25, wherein the input signal is provided as a quadrature signal and the step of providing the input signal in polar format comprises converting the input signal from quadrature to polar format.

29. A method according to any one of claims 16 to 25, wherein the input signal is provided as a channel of amplitude modulation information and a channel of phase modulation information and the step of providing the input signal in polar format comprises deriving the amplitude and phase components from the amplitude and phase modulation information channels, respectively.

30. A method according to any one of claims 16 to 29, wherein the step of deriving a bias signal comprises a step of amplifying envelope information from the amplitude component to derive the bias signal.

31. Apparatus for amplifying a signal substantially as hereinbefore described with reference to FIGS. 2, 3, 4, 5, 6, 7, 8 or 9.

32. A method of amplifying a signal substantially as hereinbefore described with reference to FIGS. 2, 3, 4, 5, 6, 7, 8 or 9.