Amplifier arrangement

• US 20030132800A1
• Filed: 11/26/2002
• Published: 07/17/2003
• Est. Priority Date: 02/08/2000
• Status: Active Grant

• Current Assignee: Andrew LLC (CommScope Holding Company, Inc.)
• Original Assignee: Wireless Systems International Ltd. (CommScope Holding Company, Inc.)
• Inventors: Kenington, Peter
• Granted Patent: US 6,819,171 B2
• Time in Patent Office: Days
• US Class Current: 330/124R
• CPC Class Codes: H03F 1/0294 using vector summing of two or more constant amplitude phase-modulated signals
• CPC Class Codes: H03F 3/2175 using analogue-digital or digital-analogue conversion H03F3/2173 takes precedence
• CPC Class Codes: H03M 1/74 Simultaneous conversion

Abstract

Limiting amplifier (116) removes amplitude variations from the input signal (110). Splitter (120) provides the constant amplitude signal to each of amplifiers (124A to 124H) via a respective switch (122A to 122H). The envelope of the input signal (110) is detected at (134) and digitised at (138). The bits of the digitised envelope signal are used to control switches (122A to 122H). The output ratings of amplifiers (124A to 124H) form a series wherein each successive output rating is twice the preceding one. Thus, the bits of the digitised envelope signal can be used to reconstruct the envelope of the output signal provided by combiner (126). Several of the amplifiers may be replaced by a single amplifier to simplify the circuit (210, FIGS. 2 and 3). The input signal may be digital removing the need for envelope detection (FIG. 4). Errors in the output may be compensated using a feedback mechanism (FIGS. 5 and 6).

Claims

1. Apparatus for amplifying an input signal to produce an output signal, the apparatus comprising splitting means for providing the input signal to each of a plurality of selectable amplifiers via a respective switch, control means for controlling the operation of the switches according to the envelope of the input signal, and a combiner for combining the selectable amplifier outputs.

9. Apparatus according to any preceding claim, wherein at least one of the selectable amplifiers has a different output rating to the other(s).

10. Apparatus according to claim 9, wherein the output ratings of the selectable amplifiers are each different and comprise a sequence wherein each successive output rating is twice the preceding one.

11. Apparatus according to any preceding claim, wherein a digital signal indicative of the envelope of the input signal is used to control the switches and the control means is arranged to associate at least one bit of the digital envelope signal with a respective switch and to use the state of the bit to operate the switch.

12. Apparatus according to claim 11, wherein the input signal is a digital, baseband signal and provides the digital envelope signal directly.

13. Apparatus according to claim 12, further comprising means for converting the input signal into an analogue signal and means for modulating the analogue input signal on to a carrier signal to produce an analogue, up-converted input signal, wherein the analogue, up-converted input signal is supplied to the splitting means.

14. Apparatus according to claim 11, further comprising means for detecting the envelope of the input signal, and means for producing the digital envelope signal by converting the detected envelope into a digital signal.

15. Apparatus according to any one of claims 11 to 14, further comprising means for providing a feedback signal by digitising the envelope of the output signal, wherein the control means is arranged to use the bits of the digitised output envelope to adapt the operation of the switches.

16. Apparatus according to any preceding claim, further comprising means for limiting the amplitude of the input signal supplied to the splitting means.

17. Apparatus according to claim 16, wherein the version of the input signal output from the limiting means has substantially constant amplitude.

18. Apparatus according to any preceding claim, further comprising filtering means arranged to reject undesired components of the combiner output.

2. Apparatus for amplifying an input signal to produce an output signal, the apparatus comprising splitting means for providing the input signal to each of a plurality of selectable amplifiers via a respective switch and to an additional amplifying means, control means for controlling the operation of the switches according to the envelope of the input signal, and a combiner for combining the amplifier outputs.

3. Apparatus according to claim 2, wherein the additional amplifying means is a linear amplifier, such as a Class A, AB or B amplifier.

4. Apparatus according to claim 2 or 3, further comprising means for modulating the input signal received by the additional amplifying means.

5. Apparatus according to claim 4, wherein the control means is arranged to adjust the modulation applied by the modulating means.

6. Apparatus according to claim 4 or 5, wherein bits of a digital signal indicative of the envelope of the input signal are used to modulate the input signal received by the additional amplifying means.

7. Apparatus according to claim 6, wherein bits of a digital signal indicative of the envelope of the output signal are used to modulate the input signal received by the additional amplifying means.

8. Apparatus according to claim 2 or 3, further comprising means for clipping the input signal received by the additional amplifying means.

19. A method of amplifying an input signal to produce an output signal, the method comprising providing the input signal to each of a plurality of selectable amplifiers via a respective switch, controlling the operation of the switches according to the envelope of the input signal, and combining the selectable amplifier outputs.

26. A method according to any one of claims 19 to 25, wherein at least one of the selectable amplifiers has a different output rating to the other(s).

27. A method according to claim 26, wherein the output ratings of the selectable amplifiers are each different and comprise a sequence wherein each successive output rating is twice the preceding one.

28. A method according to any one of claims 19 to 27, wherein a digital signal indicative of the envelope of the input signal is used to control the switches and the control step comprises associating at least one bit of the digital envelope signal with a respective switch and using the state of the bit to operate the switch.

29. A method according to claim 28, wherein the input signal is a digital, baseband signal and provides the digital envelope signal directly.

30. A method according to claim 29, further comprising converting the input signal into an analogue signal and modulating the analogue input signal onto a carrier signal to produce an analogue, up-converted input signal, wherein the analogue, up-converted input signal is provided to each of the amplifiers.

31. A method according to claim 28, further comprising detecting the envelope of the input signal, and producing the digital envelope signal by converting the detected envelope signal into a digital signal.

32. A method according to any one of claims 28 to 31, further comprising providing a feedback signal by digitising the envelope of the output signal, wherein the control step is arranged to use the bits of the digitised output envelope to adapt the operation of the switches.

33. A method according to any one of claims 19 to 32, further comprising limiting the amplitude of the input signal supplied to the splitting means.

34. A method according to claim 33, wherein the version of the input signal output from the limiting step has substantially constant amplitude.

35. A method according to any one of claims 19 to 34, further comprising filtering the output of the combining step to reject undesired components therein.

20. A method of amplifying an input signal to produce an output signal, the method comprising providing the input signal to each of a plurality of selectable amplifiers via a respective switch and to an additional amplifying means, controlling the operation of the switches according to the envelope of the input signal, and combining the amplifier outputs.

21. A method according to claim 20, wherein the additional amplifying means is a linear amplifier, such as a Class A, AB or B amplifier.

22. A method according to claim 20 or 21 further comprising modulating the input signal received by the additional amplifying means.

23. A method according to claim 22, wherein bits of a digital signal indicative of the envelope of the input signal are used to modulate the input signal received by the additional amplifying means.

24. A method according to claim 23, wherein bits of a digital signal indicative of the envelope of the output signal are used to modulate the input signal received by the additional amplifying means.

25. A method according to claim 20 or 21, further comprising clipping the input signal received by the additional amplifying means.

36. Apparatus for amplifying an input signal to produce an output signal substantially as hereinbefore described with reference to any one of FIGS. 1 to 6.

37. A method of amplifying an input signal to produce an output signal substantially as hereinbefore described with reference to any one of FIGS. 1 to 6.