Linear modulation using a linear and a non-linear amplifier
First Claim
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1. A circuit for producing at a load impedance an amplified radio frequency (RF) signal having a desired varying amplitude with improved mean efficiency of conversion of DC input power to said circuit to output signal power at said load impedance, comprising:
- a first amplifier operating in a saturated mode with constant output voltage amplitude and connected at its output through a quarter wave network to the load impedance; and
a second amplifier connected at its output to said load impedance, said second amplifier being driven to generate a modulated signal amplitude output that adds to and substracts from signal amplitude at said load impedance due to said first amplifier to produce at said load impedance the amplified RF signal.
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Abstract
A power amplifier uses a modulation technique that varies amplitude of a drive signal and, optionally, phase angle of the drive signal. The power amplifier comprises two coupled amplifiers, a first one of which is operated saturated to produce a constant voltage output. The first amplifier is coupled to a second one of the amplifiers via a quarter wave transmission line. The second amplifier is operated in a linear mode to deliver an output signal controlled by an amplitude-modulating signal. The amplitude-modulating signal may be a bipolar modulation signal that produces both positive and negative outputs from the second amplifier that add to or subtract from the output from the first amplifier to develop at a load impedance net output signal amplitudes varying between a minimum or “trough” amplitude and a maximum or “crest” amplitude. The coupling of the first and second amplifiers through a quarter-wave line allows the signal current of the second amplifier to modulate the effective load impedance seen by the first amplifier to provide efficient amplifier coupling.
103 Citations
71 Claims
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1. A circuit for producing at a load impedance an amplified radio frequency (RF) signal having a desired varying amplitude with improved mean efficiency of conversion of DC input power to said circuit to output signal power at said load impedance, comprising:
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a first amplifier operating in a saturated mode with constant output voltage amplitude and connected at its output through a quarter wave network to the load impedance; and
a second amplifier connected at its output to said load impedance, said second amplifier being driven to generate a modulated signal amplitude output that adds to and substracts from signal amplitude at said load impedance due to said first amplifier to produce at said load impedance the amplified RF signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
a radio frequency (RF) signal generator for generating an RF signal having a desired angle modulation; and
a 90°
splitter for splitting the generated RF signal into first and second phase modulated signals having a constant relative phase difference of 90°
, said first signal being connected to an input of said first amplifier and said second signal being coupled to an input of said second amplifier.
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5. A circuit as in claim 4, in which said RF signal generator generates an RF signal having a desired frequency modulation.
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6. A circuit as in claim 4, in which said RF signal generator generates an RF signal having a desired phase modulation.
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7. A circuit as in claim 4, further comprising:
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a balanced modulator having a carrier input connected to receive said second signal, an amplitude modulation input, and an output connected to said input of said second amplifier; and
an amplitude modulation generator for generating and supplying an amplitude modulation signal to said balanced modulator amplitude modulation input to control the output from said balanced modulator such that the RF signal output from said second amplifier to said load impedance corresponds to the desired varying amplitude.
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8. A circuit as in claim 4, in which said radio frequency signal generator comprises a phase-lock-loop frequency synthesizer.
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9. A circuit as in claim 7, in which said amplitude modulation generator comprises a digital signal processor.
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10. A circuit as in claim 9, in which said digital signal processor also produces an angle modulating signal.
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11. A circuit as in claim 10, in which said angle modulating signal modulates a phase output of said radio frequency signal generator.
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12. A circuit as in claim 10, in which said angle modulating signal modulates a frequency output of said radio frequency signal generator.
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13. A circuit as in claim 10, in which said angle modulating signal and said amplitude modulating signal together define analog single sideband (SSB) modulation.
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14. A circuit as in claim 10, in which said angle modulating signal and said amplitude modulating signal together define multi-level quadrature amplitude modulation.
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15. A circuit as in claim 10, in which said angle modulating signal and said amplitude modulating signal together define QPSK linear multi-phase modulation.
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16. A circuit as in claim 10, in which said angle modulating signal and said amplitude modulating signal together define OQPSK linear multi-phase modulation.
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17. A circuit as in claim 10, in which said angle modulating signal and said amplitude modulating signal together define 8-PSK linear multi-phase modulation.
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18. A circuit as in claim 1, further comprising a first quadrature modulator generating an input of the first amplifier and a second quadrature modulator generating an input of the second amplifier.
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19. A circuit as in claim 18, in which the first and second quadrature modulates output 90°
- phase shifted signals.
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20. A circuit for producing an amplified radio frequency (RF) signal having a desired varying voltage amplitude, comprising:
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a first amplifier having an input and an output;
a load impedance;
a quarter wave network coupled between said first amplifier output and said load impedance;
a second amplifier having an input and an output coupled to said load impedance intermediate said load impedance and said quarter wave network, said first and second amplifiers being operable such that each contributes at said load impedance a fraction of a desired total power output from said circuit; and
an amplifier driver circuit for generating an RF signal and for coupling the RF signal to said first and second amplifier inputs to drive said first and second amplifiers such that said first amplifier is operated in a saturated mode to produce a constant output signal amplitude that is coupled to said load impedance through said quarter wave network to develop an output signal across said load impedance due to said first amplifier, and such that said second amplifier is operated in a linear mode to produce an output signal of an amplitude varying in accordance with the amplitude of the RF signal, that is coupled to said load impedance to add to and subtract from the output signal amplitude at said load impedance due to said first amplifier, thereby to develop at said load impedance the amplified RF signal. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 44, 47, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59)
a radio frequency (RF) signal generator for generating an RF signal having a desired angle modulation; and
a 90°
splitter for splitting the generated RF angle modulated signal into first and second phase modulated signals having a constant relative phase difference of 90°
, said first signal being connected to said input to said first amplifier and said second signal being coupled to said input to said second amplifier.
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23. A circuit as in claim 22, wherein said RF signal generator generates an RF signal having a desired frequency modulation.
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24. A circuit as in claim 22, wherein said RF signal generator generates an RF signal having a desired phase modulation.
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25. A circuit as in claim 22, wherein said amplifier driver circuit further includes:
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a balanced modulator having a carrier input connected to receive said second signal, an amplitude modulation input, and an output connected to said input of said second amplifier; and
an amplitude modulation generator for supplying an amplitude modulation signal to said balanced modulator amplitude modulation input to control the output from said balanced modulator such that the RF signal output by said second amplifier to said load impedance corresponds to the desired varying amplitude.
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26. A circuit as in claim 22, in which said RE signal generator comprises a phase-lock-loop frequency synthesizer.
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27. A circuit as in claim 26, in which said amplitude modulation generator comprises a digital signal processor (DSP) producing an angle modulating signal.
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28. A circuit as in claim 27, in which said angle modulating signal modulates the phase output of said radio frequency signal generator.
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29. A circuit as in claim 27, in which said angle modulating signal modulates the frequency output of said radio frequency signal generator.
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30. A circuit as in claim 28, in which said angle modulating signal and said amplitude modulating signal together define analog single sideband (SSB) modulation.
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31. A circuit as in claim 28, in which said angle modulating signal and said amplitude modulating signal together define multi-level quadrature amplitude modulation including 16 QAM.
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32. A circuit as in claim 28, in which said angle modulating signal and said amplitude modulating signal together define linear multi-phase modulation including linear QPSK.
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33. A circuit as in claim 28, in which said angle modulating signal and said amplitude modulating signal together define linear multi-phase modulation including linear OQPSK.
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34. A circuit as in claim 28, in which said angle modulating signal and said amplitude modulating signal together define linear multi-phase modulation including 8-PSK.
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35. A circuit as in claim 20, further comprising a first quadrature modulator generating the input of the first amplifier and a second quadrature modulator generating the input of the second amplifier.
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36. A circuit as in claim 35, in which the first and second quadrature modulates output 90°
- phase shifted signals.
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44. An amplifier as in claim 36, wherein said amplifier driver circuit includes a digital signal processor (DSP) for generating said RF signal having said desired angle modulation and for generating said bipolar amplitude modulation signal.
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47. An amplifier circuit as in claim 33, wherein said amplifier driver circuit generates said RF signal to have a constant amplitude and a desired phase angle trajectory.
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49. A method as in claim 44, wherein operating the second amplifier to generate a modulated signal amplitude output comprises providing to an input of the second amplifier a drive signal having a value in accordance with a desired value of the amplified RF signal.
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50. A method as in claim 44, wherein coupling the output signal from the first amplifier through a quarter wave network to a load impedance comprises coupling the output signal from the first amplifier to the load impedance through a quarter wave transmission line having an electrical length of one quarter the wavelength of the RF signal.
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51. A method as in claim 44, further comprising:
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generating an RF signal having a desired angle modulation; and
splitting the generated RF signal into first and second phase modulated signals having a constant relative phase difference of 90°
,wherein operating the first amplifier in a saturated mode to provide a constant output signal amplitude from the amplifier comprises coupling the first signal to an input to the first amplifier, and wherein operating the second amplifier to generate a modulated signal amplitude output comprises coupling the second signal to an input to the second amplifier.
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52. A method as in claim 47, wherein generating an RF signal having a desired angle modulation comprises generating an RF signal having a desired frequency modulation.
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53. A method as in claim 47, wherein generating an RF signal having a desired angle modulation comprises generating an RF signal having a desired phase modulation.
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54. A method as in claim 47, further comprising:
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generating an amplitude modulation signal; and
controlling the amplitude of the second signal at the input to the second amplifier in accordance with the value of the amplitude modulation signal, such that an RF signal output from the second amplifier corresponds to a desired varying amplitude.
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55. A method as in claim 47, wherein generating an RF signal having a desired angle modulation comprises generating the RF signal with a phase-lock-loop synthesizer.
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56. A method as in claim 50, wherein generating an amplitude modulation signal comprises generating an amplitude modulation signal with a digital signal processor (DSP).
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57. A method as in claim 47, further comprising:
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generating an angle modulating signal; and
controlling the RF signal in accordance with the angle modulating signal to have a desired angle modulation.
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58. A method as in claim 53, wherein controlling the RF signal in accordance with the angle modulating signal to have the desired angle modulation comprises controlling the RF signal in accordance with the angle modulating signal to have a desired phase.
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59. A method as in claim 53, wherein controlling the RF signal in accordance with the angle modulating signal to have the desired angle modulation comprises controlling the RF signal in accordance with the angle modulating signal to have a desired frequency.
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37. An amplifier circuit, comprising:
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a first amplifier having an input and an output coupled to a load impedance through a quarter wave network;
a second amplifier having an input and an output coupled to said load impedance intermediate said load impedance and said quarter wave network, said first and second amplifiers being operable such that each contributes at said load impedance a fraction of a desired total power output from said circuit; and
an amplifier driver circuit for generating an RF signal having a desired angle modulation and for splitting the RF signal into first and second phase modulated signals having a constant relative phase difference of 90°
, said amplifier driver circuit coupling said first signal to said input to said first amplifier and said second signal to said input to said second amplifier to drive said first and second amplifiers such that said first amplifier is operated in a saturated mode to produce a constant output signal amplitude that is coupled to said load impedance through said quarter wave network to develop an output signal across said load impedance due to said first amplifier, and such that said second amplifier is operated in a linear mode to produce an output signal of an amplitude in accordance with the amplitude of said second signal, that is coupled to said load impedance to add to and subtract from the output signal amplitude at said load impedance due to said first amplifier, thereby to develop at said load impedance the amplified RF signal.- View Dependent Claims (38, 39, 40, 41, 42, 43, 45, 46)
a balanced modulator having a carrier input connected to receive said second signal, an amplitude modulation input, and an output connected to said input of said second amplifier; and
an amplitude modulation generator for generating and supplying an amplitude modulation signal to said balanced modulator amplitude modulation input to control the output from said balanced modulator such that the RF signal output by said second amplifier to said load impedance corresponds to a desired varying amplitude.
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40. An amplifier circuit as in claim 39, wherein said amplitude modulation generator generates and supplies a bipolar amplitude modulation signal to said amplitude modulation input to said balanced modulator that produces both positive and negative amplitudes of the signal at said input to said second amplifier.
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41. An amplifier circuit as in claim 40, wherein the bipolar amplitude modulating signal causes the output signal from said second amplifier to be of an amplitude to either add to, in the case of positive amplitudes of the output signal, or subtract from, in the case of negative amplitudes of the output signal, the output signal amplitude at said load impedance due to the output signal from said first amplifier, thereby developing at said load impedance the amplified RF signal having the desired frequency and varying in amplitude between a minimum or “
- trough”
amplitude and a maximum or “
crest”
amplitude.
- trough”
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42. An amplifier circuit as in claim 37, wherein said first signal developed by said amplifier driver circuit is of constant amplitude and said second signal is linearly related to the desired varying signal amplitude at said load impedance.
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43. An amplifier circuit as in claim 37, wherein said constant relative phase difference of 90°
- between said first and second signals causes the outputs of said first and second amplifiers to be in phase at said load impedance.
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45. An amplifier circuit as in claim 40, wherein said DSP generates said RF signal to have a desired phase modulation.
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46. An amplifier circuit as in claim 40, wherein said DSP generates said RF signal to have a desired frequency modulation.
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48. A method of producing am amplified radio frequency (RF) signal having a desired varying amplitude from the amplifier;
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coupling the output signal from the first amplifier through a quarter wave network to a load impedance;
operating a second amplifier to generate a modulated signal amplitude output; and
coupling the output signal fro the second amplifier to the load impedance such that the output from the second amplifier adds to and substracts from the signal amplitude at the load impedance due to the first amplifier to produce at the load impedance the amplified RF signal. - View Dependent Claims (60, 61)
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62. A method of amplifying a radio frequency (RF) signal, comprising:
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coupling an output from a first amplifier to a load impedance through a quarter wave network;
coupling an output from a second amplifier to the load impedance intermediate the load impedance and the quarter wave network;
generating an RF signal;
splitting the RF signal into first and second phase modulated signals having a constant relative phase difference of 90°
;
coupling the first signal to the input to the first amplifier to operate the first amplifier in a saturated mode to produce a constant amplitude signal output that is coupled to the load impedance through the quarter wave network to develop a signal amplitude across the load impedance due to the first amplifier; and
coupling the second signal to the input to the second amplifier to operate the second amplifier in a linear mode to produce from the second amplifier an output signal, of an amplitude in accordance with the amplitude of the second signal, that is coupled to the load impedance to add to and subtract from the amplitude of the signal at the load impedance due to the first amplifier, thereby to develop at the load impedance the amplified RF signal. - View Dependent Claims (63, 64, 65, 66, 67, 68, 69, 70, 71)
generating an amplitude modulation signal; and
controlling the amplitude of the second signal at the input to the second amplifier in accordance with the value of the amplitude modulation signal, such that an RF signal output from the second amplifier to the load impedance corresponds to a desired varying amplitude.
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66. A method as in claim 62, further comprising:
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generating a bipolar amplitude modulation signal; and
controlling the amplitude of the second signal at the input to the second amplifier in accordance with the value of the bipolar amplitude modulation signal, such that the second signal has both positive and negative amplitudes at the input to the second amplifier.
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67. A method as claimed in claim 66, wherein the bipolar amplitude modulation signal causes the output signal from the second amplifier to be of an amplitude to either add to, in the case of positive amplitudes of the output signal, and subtract from, in the case of negative amplitudes of the output signal, the signal amplitude across the load impedance due to the output signal from the first amplifier, thereby developing at the load impedance the amplified RF signal having the desired frequency and varying in amplitude between a minimum or “
- trough”
amplitude and a maximum or “
crest”
amplitude.
- trough”
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68. A method as in claim 62, wherein generating an RF signal generates a constant amplitude RF signal.
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69. A method as in claim 62, wherein generating an RF signal generates an RF signal having a desired phase modulation.
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70. A method as in claim 62, wherein generating an RF signal generates an RF signal having a desired frequency modulation.
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71. A method as in claim 62, wherein generating an RF signal generates an RF signal having a constant amplitude and a desired phase angle trajectory.
Specification
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Current AssigneeUnwired Planet LLC (JP Morgan Chase & Co)
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Original AssigneeEricsson, Inc. (Telefonaktiebolaget LM Ericsson)
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InventorsCamp, William O. Jr., Dent, Paul W.
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Primary Examiner(s)Pascal, Robert
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Assistant Examiner(s)Choe, Henry
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Application NumberUS09/710,537Time in Patent Office495 DaysField of Search330/124.R, 330/295, 330/129, 332/149, 332/103, 332/144, 455/108, 455/111, 375/268, 375/269US Class Current330/124.00RCPC Class CodesH03F 1/0288 using a main and one or sev...H03F 1/0294 using vector summing of two...
