Distortion-managed digital RF communications transmitter and method therefor
First Claim
1. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components, said method comprising:
- obtaining a forward-data stream configured to convey digital information;
down-converting a feedback signal obtained from said analog-transmitter components using a digital-subharmonic-sampling downconverter to generate a return-data stream;
training a linear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components to compensate for linear distortion introduced by said analog-transmitter components, said linear predistorter training activity including determining filter coefficients for an equalizer which filters said forward-data stream and processing said return-data-stream to generate said filter coefficients; and
training a nonlinear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components to compensate for nonlinear distortion introduced by said analog-transmitter components.
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Accused Products
Abstract
A digital communications transmitter (100) includes a digital linear-and-nonlinear predistortion section (200) to compensate for linear and nonlinear distortion introduced by transmitter-analog components (120). A direct-digital-downconversion section (300) generates a complex digital return-data stream (254) from the analog components (120) without introducing quadrature imbalance. A relatively low resolution exhibited by the return-data stream (254) is effectively increased through arithmetic processing. Linear distortion is first compensated using adaptive techniques with an equalizer (246) positioned in the forward-data stream (112). Nonlinear distortion is then compensated using adaptive techniques with a plurality of equalizers (226) that filter a plurality of orthogonal, higher-ordered-basis functions (214) generated from the forward-data stream (112). The filtered-basis functions are combined together and subtracted from the forward-data stream (112).
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Citations
50 Claims
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1. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components, said method comprising:
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obtaining a forward-data stream configured to convey digital information; down-converting a feedback signal obtained from said analog-transmitter components using a digital-subharmonic-sampling downconverter to generate a return-data stream; training a linear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components to compensate for linear distortion introduced by said analog-transmitter components, said linear predistorter training activity including determining filter coefficients for an equalizer which filters said forward-data stream and processing said return-data-stream to generate said filter coefficients; and training a nonlinear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components to compensate for nonlinear distortion introduced by said analog-transmitter components. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A digital communications transmitter comprising:
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a source of a forward-data stream configured to digitally convey information; a nonlinear predistorter coupled to said forward-data-stream source and configured to generate a nonlinear-predistorted-compensation stream from said forward-data stream; a combiner coupled to said forward-data-stream source and said nonlinear predistorter and configured to generate a nonlinear-predistorted-forward-data stream from said forward-data stream and said nonlinear-predistorted-compensation stream; a linear predistorter coupled to said combiner and configured to generate a linear-and-nonlinear-predistorted-forward-data stream, said linear-and-nonlinear-predistorted-forward-data stream being routed to analog-transmitter components; and a feedback section having an input adapted to receive an RF-analog signal from said analog-transmitter components and an output coupled to said nonlinear predistorter and to said linear predistorter. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A digital communications transmitter comprising:
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analog transmitter components; a feedback section adapted to receive an RF-analog signal from said analog-transmitter components; a linear predistorter coupled to said feedback section, said linear predistorter being configured to predistort a forward-data stream that digitally conveys information to compensate for linear distortion introduced downstream of said linear predistorter by said analog-transmitter components; a nonlinear predistorter coupled to said feedback section, said nonlinear predistorter being configured to predistort said forward-data stream to compensate for nonlinear distortion introduced downstream of said nonlinear predistorter by said analog-transmitter components; and a combiner coupled to said linear predistorter and said nonlinear predistorter. - View Dependent Claims (30, 31, 32, 33, 34)
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35. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components, said method comprising:
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obtaining a forward-data stream configured to convey digital information; obtaining an RF-analog signal from said analog-transmitter components; generating a return-data stream from said RF-analog signal; forming an error signal by combining said forward-data stream and said return-data stream; implementing a first-estimation-and-convergence algorithm responsive to said error signal to train a linear predistorter to compensate for linear distortion introduced by said analog-transmitter components; and implementing a second-estimation-and-convergence algorithm responsive to said error signal to train a non-linear predistorter to compensate for nonlinear distortion introduced by said analog-transmitter components. - View Dependent Claims (36, 37, 38, 39)
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40. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components, said method comprising:
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providing a linear predistorter located upstream of said analog-transmitter components; providing a nonlinear predistorter located upstream of said analog-transmitter components; obtaining a forward-data stream configured to convey digital information, said forward-data stream being obtained upstream of said linear predistorter and upstream of said nonlinear predistorter; generating a return-data stream from a feedback signal obtained from said analog-transmitter components; training said linear predistorter in response to said forward-data stream and said return-data stream to compensate for linear distortion introduced by said analog-transmitter components; and training said nonlinear predistorter in response to said forward-data stream and said return-data stream to compensate for nonlinear distortion introduced by said analog-transmitter components.
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41. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components that include a power amplifier which produces a power-amplifier-output signal, said method comprising:
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obtaining a forward-data stream provided by a peak-reduction section and configured to convey digital information; training a linear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components to compensate for linear distortion introduced by said analog-transmitter components; training a nonlinear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components to compensate for nonlinear distortion introduced by said analog-transmitter components; obtaining an residual value that estimates uncompensated nonlinear distortion introduced by said analog-transmitter components into said power-amplifier-output signal; and operating said peak-reduction section so that an amount of peak reduction imposed in said forward-data stream is responsive to said residual value. - View Dependent Claims (42)
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43. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components, said method comprising:
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obtaining a forward-data stream configured to convey digital information; obtaining a return-data stream from said analog-transmitter components; training a linear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components by processing said return-data stream to compensate for linear distortion introduced by said analog-transmitter components; and training a nonlinear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components by processing said return-data stream to compensate for nonlinear distortion introduced by said analog-transmitter components; wherein said forward-data stream exhibits a forward resolution and said return-data stream exhibits a return resolution less than said forward resolution.
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44. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components, said method comprising:
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obtaining a forward-data stream configured to convey digital information; obtaining a return-data stream from said analog-transmitter components; training a linear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components by implementing an estimation-and-convergence algorithm responsive to said forward-data stream and to said return-data stream to compensate for linear distortion introduced by said analog-transmitter components; and training a nonlinear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components by implementing an estimation-and-convergence algorithm responsive to said forward-data stream and to said return-data stream to compensate for nonlinear distortion introduced by said analog-transmitter components; wherein said forward-data stream and said return-data stream exhibit forward-error and return-error levels, respectively, with said return-error level being greater than said forward-error level, and said estimation-and-convergence algorithms control a rate of convergence to achieve a predetermined effective return-error level that is less than said return-error level.
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45. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components, said method comprising:
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obtaining a forward-data stream configured to convey digital information; obtaining a return-data stream from said analog-transmitter components; training a linear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components by implementing an estimation-and-convergence algorithm responsive to said forward-data stream and to said return-data stream to compensate for linear distortion introduced by said analog-transmitter components; and training a nonlinear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components by implementing an estimation-and-convergence algorithm responsive to said forward-data stream and to said return-data stream to compensate for nonlinear distortion introduced by said analog-transmitter components; wherein said estimation-and-convergence algorithms estimate filter coefficients which influence said forward-data and return-data streams, generate an error signal by combining said forward-data and return-data streams, and repetitively revise said filter coefficients to minimize said error signal and to decorrelate said error signal from said forward-data stream.
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46. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components, said method comprising:
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obtaining a forward-data stream configured to convey digital information; obtaining a return-data stream from said analog-transmitter components; delaying said forward-data stream to form a delayed-forward-data stream in temporal alignment with said return-data stream; forming an error signal by combining said delayed-forward-data stream and said return-data stream; training a linear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components to compensate for linear distortion introduced by said analog-transmitter components; training a nonlinear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components to compensate for nonlinear distortion introduced by said analog-transmitter components; and performing said linear-predistorter-training and nonlinear-predistorter-training activities by implementing an estimation-and-convergence algorithm that converges upon filter coefficients which minimize said error signal. - View Dependent Claims (47, 48)
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49. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components, said method comprising:
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obtaining a forward-data stream configured to convey digital information; training a linear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components to compensate for linear distortion introduced by said analog-transmitter components; and training a nonlinear predistorter which is responsive to said forward-data stream and is located upstream of said analog-transmitter components to compensate for nonlinear distortion introduced by said analog-transmitter components, wherein said nonlinear-predistorter-training activity comprises; generating a plurality of basis-function-data streams, wherein each basis-function-data stream is responsive to X(n)·
|X(n)|K, where X(n) represents said forward-data stream, and K is an integer greater than or equal to one;estimating filter coefficients for filters that process said basis-function streams; filtering said basis-function-data streams in said filters to generate a plurality of filtered-basis-function-data streams; combining said filtered-basis-function-data streams and said forward-data stream; and repetitively revising said filter coefficients to compensate for said nonlinear distortion.
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50. A method of managing distortion in a digital communications transmitter in which at least a portion of said distortion is introduced by analog-transmitter components that include a power amplifier which produces a power-amplifier-output signal, said method comprising:
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obtaining a forward-data stream provided by a peak-reduction section and configured to convey digital information; obtaining an RF-analog signal from said analog-transmitter components; generating a return-data stream from said RF-analog signal; implementing a first-estimation-and-convergence algorithm to train a linear predistorter to compensate for linear distortion introduced by said analog-transmitter components; implementing a second-estimation-and-convergence algorithm to train a non-linear predistorter to compensate for nonlinear distortion introduced by said analog-transmitter components; obtaining an residual value that estimates uncompensated nonlinear distortion introduced by said analog-transmitter components into said power-amplifier-output signal; and operating said peak-reduction section so that an amount of peak reduction imposed in said forward-data stream is responsive to said residual value.
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Specification