Electronically tuned power amplifier

• US 7,202,734 B1
• Filed: 07/06/2000
• Issued: 04/10/2007
• Est. Priority Date: 07/06/1999
• Status: Expired due to Fees

• Current Assignee: Frederick Herbert Raab
• Original Assignee: Frederick Herbert Raab
• Inventors: Raab, Frederick Herbert
• Primary Examiner(s): Shingleton; Michael B
• Application Number:
  US09/610,933
• Time in Patent Office: 2,469 Days
• Field of Search: 330/126, 330/192, 330/302, 330/305, 330/306, 330/284, 455/74, 455/107, 455/121, 455/129
• US Class Current: 330/126
• CPC Class Codes: H03F 2200/387 A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
• CPC Class Codes: H03F 2200/391 the output circuit of an amplifying stage comprising an LC-network
• CPC Class Codes: H03F 3/04 with semiconductor devices only
• CPC Class Codes: H03F 3/191 Tuned amplifiers H03F3/193, H03F3/195 take precedence

Abstract

A circuit and method for electronically tuning an RF power amplifier. The output filter includes at least one electronically variable reactance. The electronically tuned power amplifier may be tuned rapidly to a selected frequency, to a selected impedance, or to produce a selected output amplitude. An optional controller translates frequency, impedance, or modulation inputs into tuning signals. High-efficiency, wideband amplitude modulation is produced by varying the amplifier load impedance along preferred loci.

Claims

1. An electronically tuned circuit, comprising a power amplifier having an amplifier output wherein said amplifier output is coupled to provide amplified signal to an electronically tunable output network, said power amplifier capable of being operated in a large-signal mode, said output network including an electronically tunable reactive component, a control line, and a control input, wherein said control input is connected to a time varying non-DC tuning input signal, wherein electronic tuning of said electronically tunable reactive component includes non-motor operated electronic tuning when said power amplifier is operated in said large-signal mode, wherein said control line extends to said electronically tunable reactive component for providing a control signal derived from said time varying tuning input signal, wherein said control signal varies over more than two values for electronically varying reactance of said electronically tunable reactive component over more than two values, wherein said time varying non-DC tuning input signal is not derived from said amplified output.

2. An electronically tuned circuit as in claim 1, wherein said varying reactance of said electronically tunable reactive component tunes said output network to a selected frequency.

3. An electronically tuned circuit as in claim 1, wherein said varying reactance of said electronically tunable reactive component tunes said output network to maintain a match between said output network and a varying load impedance.

4. An electronically tuned circuit as in claim 1, wherein said varying reactance of said electronically tunable reactive component adds modulation to a large signal in said output network.

5. An electronically tuned circuit as in claim 4, wherein said varying reactance of said reactive component provides a power-amplifier load-impedance locus that substantially maximizes power-amplifier efficiency.

6. An electronically tuned circuit as in claim 5 wherein said varying reactance of said reactive component causes said power-amplifier load impedance to follow a substantially resistive locus, thereby maintaining power-amplifier efficiency near maximum.

7. An electronically tuned circuit as in claim 1, wherein said varying reactance of said reactive component tunes said output network in accordance with a predetermined set of tuning inputs.

8. An electronically tuned circuit as in claim 7, wherein said tuning inputs are selected in accordance with a lookup table.

9. An electronically tuned circuit as in claim 1, wherein said varying reactance of said reactive component tunes said output network in accordance with a predetermined lookup table of tuning inputs.

10. An electronically tuned circuit as in claim 1, wherein said varying reactance of said reactive component tunes said output network in accordance with a sample of the amplifier output.

11. An electronically tuned circuit as in claim 1, wherein said varying reactance of said reactive component tunes said output network in accordance with a sample of the network output.

12. An electronically tuned circuit as in claim 1, wherein said varying reactance of said reactive component tunes said output network in accordance with a sample of a radiated signal.

13. An electronically tuned circuit as in claim 1, wherein said electronically tunable reactive component includes an electronically tunable capacitor.

14. An electronically tuned circuit as in claim 13, wherein said electronically tunable capacitor includes a transistor.

15. An electronically tuned circuit as in claim 13, wherein said electronically tunable capacitor includes a diode.

16. An electronically tuned circuit as in claim 13, wherein said electronically tunable capacitor includes a diode having a control terminal.

17. An electronically tuned circuit as in claim 13, wherein said electronically tunable capacitor includes a micro electro-mechanical system device.

18. An electronically tuned circuit as in claim 13, wherein said electronically tunable capacitor includes a variable-dielectric material.

19. An electronically tuned circuit as in claim 13, wherein said electronically tunable capacitor includes a piezo-electric device.

20. An electronically tuned circuit as in claim 1, wherein said electronically tunable reactive component includes at least one inductive component adapted to be electronically tuned in inductance.

21. An electronically tuned circuit as in claim 20, wherein said at least one inductive component includes a variable-permeability core.

22. An electronically tuned circuit as in claim 20, wherein said at least one inductive component includes a piezo-electric device.

23. An electronically tuned circuit as in claim 1, wherein said electronically tunable reactive component includes at least one transmission line adapted to be electronically tuned in electrical characteristics.

24. An electronically tuned circuit as in claim 23, wherein said at least one transmission-line includes an electrically variable dielectric material.

25. An electronically tuned circuit as in claim 23, wherein said at least one transmission-line includes an electrically variable magnetic material.

26. An electronically tuned circuit as in claim 1, further comprising a passive filter coupled to said output network for removing undesired harmonic frequencies.

27. An electronically tuned circuit as in claim 1, wherein said power amplifier includes an amplifier input, further comprising a second electronically tunable reactive component coupled to said amplifier input for tuning said amplifier input.

28. An electronically tuned circuit as in claim 1, further comprising a controller, said controller for providing a signal for controlling said electronically tunable output network.

29. An electronically tuned circuit as in claim 28, wherein said controller includes a controller input, further comprising an envelope detector with an envelope-detector input and envelope-detector output, said envelope-detector output coupled to said controller input, said envelope detector being responsive to an input RF signal and providing a modulation input to said controller.

30. An electronically tuned circuit as in claim 28, further comprising a drive-level adjustor coupled for adjusting amplitude of a signal provided to said power amplifier.

31. An electronically tuned circuit as in claim 1, further comprising a digital signal processor coupled to said power amplifier and to said electronically tunable output network, said processor for providing a drive signal to said power amplifier and said time varying tuning input signal to said electronically tunable output network.

32. An electronically tuned circuit as in claim 31, further comprising a controller coupled to said digital signal processor and to said electronically tunable output network, wherein output of said digital signal processor is directed to said controller and wherein output of said controller is directed to said electronically tunable output network.

33. An electronically tuned circuit as in claim 1, further comprising a drive-level adjustor coupled for adjusting amplitude of a signal provided to said power amplifier.

34. An electronically tuned circuit as in claim 33, wherein said varying reactance of said reactive component and said drive-level adjuster add modulation to a large signal in said output network.

35. An electronically tuned circuit as in claim 34, wherein when said time varying tuning input signal has an amplitude that is above a threshold said electronically tunable output network is used to control amplitude and when said time varying tuning input signal is below a threshold said drive level adjuster is used to control amplitude.

36. An electronically tuned circuit as in claim 33, further comprising a controller for converting said time varying tuning input signal into tuning signals for control of said electronically tunable reactive component.

37. An electronically tuned circuit as in claim 1, further comprising a bias input for controlling bias level of said power amplifier.

38. An electronically tuned circuit as in claim 37, wherein said bias level is controlled to equal a minimum level necessary to enable operation of said power amplifier, thereby reducing power consumption.

39. An electronically tuned circuit as in claim 37, further comprising a controller for adjusting said bias level in response to at least one from the group including frequency, impedance, and modulation inputs.

47. An electronically tuned circuit as in claim 1, comprising a plurality of amplifier subsystems, wherein each of said amplifier subsystems includes one said power amplifier coupled to an electronically tunable output network, wherein said amplifier subsystems are coupled to a power combiner for delivery of signals from said amplifier subsystems to a common load.

48. An electronically tuned power amplifier system as in claim 47, wherein each said varying reactance of each said electronically tunable reactive component tunes said output network to a selected frequency.

49. An electronically tuned power amplifier system as in claim 47, wherein each said varying reactance of said electronically tunable reactive component tunes said output network to match a desired load impedance.

50. An electronically tuned power amplifier system as in claim 47, wherein each said varying reactance of each said electronically tunable reactive component adds modulation to a large signal in each said output network.

51. An electronically tuned power amplifier system as in claim 47, wherein said output networks are adapted to cancel reactances resulting from combining said signals.

52. An electronically tuned power amplifier system as in claim 47, further comprising a controller for generating drive and control signals for each subsystem.

53. An electronically tuned power amplifier system as in claim 52, wherein said controller is adapted to generating drive signals of different phases for production of an amplitude-modulated system output.

54. An electronically tuned power amplifier system as in claim 52, wherein said output networks are adapted to cancel time varying reactances resulting from combining out-of-phase signals.

55. An electronically tuned power amplifier as in claim 47, further comprising a passive filter coupled to said power combiner for removing undesired harmonic frequencies and distortion products.

60. An electronically tuned circuit as in claim 1, wherein said output network includes at least two reactive components connected as a tuned circuit, wherein said electronically tunable reactive component includes at least one of said reactive components.

61. An electronically tuned circuit as in claim 28, wherein said controller converts an input signal to a voltage suitable for controlling said tunable output.

62. An electronically tuned circuit as in claim 1, wherein said electronically tunable reactive component is continuously variable.

40. An electronically tuned circuit comprising:

(a) means for power amplifying having an output, wherein said means for power amplifying comprises a large-signal mode; and

(b) means for electronic tuning of said means for power amplifying when said means for power amplifying is operating in said large signal mode, wherein said means for electronic tuning is coupled to said means for power amplifying for receiving an amplified signal, wherein said means for electronic tuning comprises an electronically tunable reactive component, a control line, and a control input, said control input available for connection from external to said means for electronic tuning, further wherein said control input is connected to a time varying non-DC tuning input signal, wherein said electronically tunable reactive component includes non-motor operated electronic tuning, wherein said control line extends to said electronically tunable reactive component for providing a control signal derived from said time varying non-DC tuning input signal, wherein said control signal varies over more than two values for electronically varying reactance of said electronically tunable reactive component over more than two values, wherein said time varying non-DC tuning input signal is not derived from said means for amplifying output.

41. An electronically tuned circuit as in claim 40, wherein said means for power amplifying operates in class E and said electronic-tuning means is capable of being tuned to provide a reactance for optimum class-E operation for a selected frequency.

42. An electronically tuned circuit as in claim 40, wherein said means for power amplifying operates in class E and said electronic-tuning means is capable of being tuned to provide a reactance for optimum class-E operation while delivering power to a selected load impedance.

43. An electronically tuned circuit as in claim 40, wherein said means for power amplifying operates in class E and said electronic-tuning means is capable of being tuned to provide a reactance for optimum class-E operation while simultaneously modulating the output of said electronic-tuning means.

44. An electronically tuned circuit as in claim 40, wherein said means for power amplifying operates in class E and further comprising a fixed reactance for optimum class-E operation at a first frequency, wherein said means for electronic tuning is capable of being tuned to provide said power amplifying means with a load impedance for optimum class-E operation for a selected second frequency.

45. An electronically tuned circuit as in claim 40, wherein said means for power amplifying operates in class E and further comprising a fixed reactance for optimum class-E operation with a first load impedance, wherein said means for electronic tuning is capable of being tuned to provide said power amplifying means with a load impedance for optimum class-E operation with a second load impedance different from said first load impedance.

46. An electronically tuned circuit as in claim 40, wherein said means for electronic tuning is connected to an output terminal, wherein said means for power amplifying operates in class E and said means for electronic tuning is capable of being tuned to provide an impedance for optimum class-E operation when said output terminal is delivering a maximum output signal amplitude, and said means for electronic tuning is capable of being tuned to provide suboptimum class E operation when said output terminal is delivering less than a maximum output signal amplitude.

63. An electronically tuned circuit as in claim 40, wherein said electronically tunable reactive component is continuously variable.

56. An electronically tuned circuit, comprising one or more power amplifiers having an output, wherein said power amplifiers are capable of operating in a large-signal mode, further wherein said one or more power amplifiers has an output network for receiving an amplified signal, said output network including a tuning input, a network output, an electronically tunable reactive component, a control line, wherein said tuning input is connected to a time varying non-DC tuning input signal, wherein electronic tuning of said electronically tunable reactive component includes non-motor operated electronic tuning when said one or more power amplifiers are operating in said large-signal mode, wherein said control line extends to said electronically tunable reactive component for providing a control signal derived from said time varying non-DC tuning input signal, wherein said control signal varies over more than two values for electronically varying reactance of said electronically tunable reactive component over more than two values, wherein said time varying non-DC tuning input signal is not derived from said amplifier output.

57. An electronically tuned circuit as in claim 56, wherein said varying reactance of said electronically tunable reactive component tunes said output network to a fixed or variable frequency.

58. An electronically tuned circuit as in claim 56, wherein said varying reactance of said electronically tunable reactive component tunes said output network to maintain a match with a varying load impedance at said network output.

59. An electronically tuned circuit as in claim 56, wherein said varying reactance of said electronically tunable reactive component adds modulation to a large signal in said output network.

64. An electronically tuned circuit as in claim 56, wherein said electronically tunable reactive component is continuously variable.