US5760646A
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Feed-forward correction loop with adaptive predistortion injection for linearization of RF power amplifier
Assignee: Intel Corp
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Filing: 1996-07-23
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Granted: 1998-06-02
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Expires: 2016-07-23
Abstract
Abstract A linearization scheme for an RF power amplifier combines an adaptive predistortion modulator with a feedforward error correction loop, which cancels noise imparted by predistortion modulation to the amplified signal, and minimizes distortion in the RF amplifier's output to a level that allows the use of a low cost auxiliary RF error amplifier in the feed-forward loop. The predistortion correction mechanism produces a predistortion signal based upon the input signal and is adaptively adjusted by an error signal extracted from the output of the a main RF power amplifier. The input signal is supplied to a work function generator unit and to a subtraction unit, which is also coupled to receive a fractional portion of the amplifier output signal and outputs the RF error component. The RF error component is coupled to a predistortion function generator, which is driven by the work function generator unit. The predistortion modulator uses the output of the predistortion function generator to predistort the input signal by a compensation characteristic equal and opposite to the distortion expected at the output of the main RF amplifier. When subjected to the transfer function of the RF amplifier, the predistortion signal injected into the input signal path will effectively cancel the amplifier's anticipated distortion behavior. The predistortion is made adaptive by tracking the error signal and coupling this error signal to the predistortion function generator.
Inventors
- 👤 Donald K. Belcher
- 👤 Michael A. Wohl
- 👤 Kent E. Bagwell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 16:16
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/32; H03F1/3241; H03F1/3258; H03F1/3223; H03F1/3229; H03F1/3247; H03F2200/00; H03F2200/102; H03F2200/438; H03F2201/00; H03F2201/32; H03F2201/3212; H03F2201/3233
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
196 words
A method for correcting for distortion in an RF power amplifier comprising the steps of: (a) monitoring an input signal supplied to and an amplified output signal from by said RF power amplifier, and extracting therefrom a distortion signal that varies with a rate of variation of the envelope of said amplified output signal; (b) monitoring the instantaneous amplitude of said input signal to said amplifier, and generating at least one work function that varies with a variation of the instantaneous amplitude of said input signal; c) generating a predistortion function in accordance with said distortion signal extracted in step (a) and said at least one work function of the instantaneous amplitude of said input signal as generated in step (b), so that said predistortion function varies with a rate of variation of the envelope of said amplified output signal; (d) adaptively predistorting said input signal to be amplified by said RF amplifier at a rate of variation of the envelope of said amplified output signal, by predistorting said input signal by said predistortion function generated in step (c); and (e) subjecting said amplified output signal from said RF power amplifier to a feed-forward correction loop.
Claim 2
Independent Claim
196 words
A method for correcting for distortion in an RF power amplifier comprising the steps of: (a) monitoring an input signal supplied to and an amplified output signal from by said RF power amplifier, and extracting therefrom a distortion signal that varies with a rate of variation of the envelope of said amplified output signal; (b) monitoring the instantaneous amplitude of said input signal to said amplifier, and generating at least one work function that varies with a variation of the instantaneous amplitude of said input signal; c) generating a predistortion function in accordance with said distortion signal extracted in step (a) and said at least one work function of the instantaneous amplitude of said input signal as generated in step (b), so that said predistortion function varies with a rate of variation of the envelope of said amplified output signal; (d) adaptively predistorting said input signal to be amplified by said RF amplifier at a rate of variation of the envelope of said amplified output signal, by predistorting said input signal by said predistortion function generated in step (c); and (e) subjecting said amplified output signal from said RF power amplifier to a feed-forward correction loop.
Claim 3
Dependent Claim
46 words
A method according to claim 1 wherein step (e) comprises combining said distortion signal extracted in step (a) with said amplified output signal from said RF power amplifier, so as to effectively cancel the distortion signal of said amplified output signal by said RF power amplifier.
Claim 4
Dependent Claim
40 words
A method according to claim 2, wherein step (e) comprises amplifying said distortion signal further extracted in step (a) by means of an auxiliary RF error amplifier having an operational power range less than that of said RF power amplifier.
Claim 5
Dependent Claim
33 words
A method according to claim 3, wherein said feed-forward correction loop includes a subtraction unit coupled to the output of said RF amplifier and to the output of said auxiliary RF error amplifier.
Claim 6
Dependent Claim
29 words
A method according to claim 1, wherein said predistortion function has a distortion compensation characteristic that is generally complementary to distortion expected at the output of said RF amplifier.
Claim 7
Dependent Claim
63 words
A method according to claim 5, wherein step (b) comprises generating a plurality of respectively different work functions of said monitored input signal, and step (c) comprises controllably adjusting said plurality of respectively different work functions in accordance with said distortion signal extracted in step (a), and generating said predistortion function in accordance with a combination of controllably adjusted respectively different work functions.
Claim 8
Dependent Claim
46 words
A method according to claim 6, wherein step (c) further comprises generating a plurality of weights in accordance with a distortion signal minimization mechanism that is operative to reduce said distortion signal, and adjusting said plurality of respectively different work functions in accordance with said weights.
Claim 9
Dependent Claim
28 words
A method according to claim 7, wherein step (a) further includes applying said input signal and said output signal to a coherent receiver to extract said distortion signal.
Claim 10
Dependent Claim
34 words
A method according to claim 1, wherein said predistortion function is controllably weighted by respective amplitude and phase component-associated weighting coefficients generated in accordance with said distortion signal in said RF amplifier's output signal.
Claim 11
Dependent Claim
233 words
A signal processing system for correcting for distortion in an RF power amplifier comprising: a work function generator coupled to receive an input signal to be amplified by said RF power amplifier and being operative to generate at least one work function that varies with a variation of the instantaneous amplitude of said input signal; a distortion signal extraction unit which is coupled to monitor said input signal and an amplified output signal from by said RF power amplifier, and to extract therefrom a distortion signal that varies with a rate of variation of the envelope of said amplified output signal; a predistortion function generator, coupled to said work function generator and to said distortion signal extraction unit, and being operative to generate a predistortion function in accordance with said distortion signal and said at least one work function of the instantaneous amplitude of said input signal, so that said predistortion function varies with a rate of variation of the envelope of said amplified output signal; a predistortion modulator coupled in the path of an input signal to be amplified by said RF power amplifier, and being operative to adaptively predistort said input signal at a rate of variation of the envelope of said amplified output signal, by predistorting said input signal by said predistortion control function; and a feed-forward correction loop connected in circuit with an output of said RF power amplifier.
Claim 12
Dependent Claim
233 words
A signal processing system for correcting for distortion in an RF power amplifier comprising: a work function generator coupled to receive an input signal to be amplified by said RF power amplifier and being operative to generate at least one work function that varies with a variation of the instantaneous amplitude of said input signal; a distortion signal extraction unit which is coupled to monitor said input signal and an amplified output signal from by said RF power amplifier, and to extract therefrom a distortion signal that varies with a rate of variation of the envelope of said amplified output signal; a predistortion function generator, coupled to said work function generator and to said distortion signal extraction unit, and being operative to generate a predistortion function in accordance with said distortion signal and said at least one work function of the instantaneous amplitude of said input signal, so that said predistortion function varies with a rate of variation of the envelope of said amplified output signal; a predistortion modulator coupled in the path of an input signal to be amplified by said RF power amplifier, and being operative to adaptively predistort said input signal at a rate of variation of the envelope of said amplified output signal, by predistorting said input signal by said predistortion control function; and a feed-forward correction loop connected in circuit with an output of said RF power amplifier.
Claim 13
Dependent Claim
71 words
A signal processing system according to claim 10, wherein said feed-forward correction loop includes an RF error amplifier which amplifies said distortion signal extracted by said distortion signal extraction unit, and a signal combining unit which is coupled to subtract said distortion signal from said amplified output signal from said RF power amplifier, so as to effectively cancel the distortion signal in said amplified output signal from said RF power amplifier.
Claim 14
Dependent Claim
26 words
A signal processing system according to claim 11, wherein said RF error amplifier has an operational power range less than that of said RF power amplifier.
Claim 15
Dependent Claim
31 words
A signal processing system according to claim 10, wherein said predistortion function has a distortion compensation characteristic that is generally complementary to distortion expected at the output of said RF amplifier.
Claim 16
Dependent Claim
34 words
A signal processing system according to claim 10, wherein said predistortion modulator is operative to adaptively adjust respective amplitude and phase components of said input signal to be amplified by said RF power amplifier.
Claim 17
Dependent Claim
68 words
A signal processing system according to claim 10 wherein said work function generator is operative to generate a plurality of respectively different work functions of said input signal, said predistortion function generator is operative to controllably adjust said plurality of respectively different work functions in accordance with said distortion signal and to generate said predistortion function in accordance with a combination of controllably adjusted respectively different work functions.
Claim 18
Dependent Claim
49 words
A signal processing system according to claim 15, wherein said predistortion function generator is operative to generate a plurality of weights in accordance with a distortion signal minimization mechanism that reduces said distortion signal, and to adjust said plurality of respectively different work functions in accordance with said weights.
Claim 19
Dependent Claim
18 words
A signal processing system according to claim 10, wherein said distortion signal extraction unit includes a coherent receiver.
Claim 20
Dependent Claim
52 words
A signal processing system according to claim 10, wherein said distortion signal extraction unit is operative to measure energy in a prescribed spectral portion of the output signal produced by said RF amplifier, so as to derive a frequency domain measure of distortion contained in the output signal of said RF amplifier.
Claim 21
Dependent Claim
61 words
A signal processing system according to claim 10, wherein said distortion signal extraction unit includes a bandpass filter which has a frequency pass band exclusive of a desired frequency content of said output signal is and is operative to provide a measure of energy contained in said pass band indicative of distortion in the output signal amplified by said RF amplifier.
References Cited (Backward Citations)
US4943783A
Cited
US5157345A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-06-01 | 2001-12-01 | 2002-06-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-06-01 | 2005-12-01 | 2006-06-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-06-01 | 2009-12-01 | 2010-06-02 | $7700.00 | Window Closed / Lapsed |