Polyphase nonlinear digital predistortion
AssigneeMassachusetts Institute of Technology
InventorsJoel I. Goodman, Benjamin A. Miller, Matthew A. Herman, James E. Vian
Life of this patent
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Abstract
Polyphase nonlinear digital predistorters (pNDPs) mitigate nonlinear distortions generated by time-interleaved digital-to-analog converters (TIDACs). Processors in an example pNDP compute nonlinear and linear compensation terms representative of channel mismatches and other imperfections in the TIDAC based on the digital input to the TIDAC. The pNDP subtracts these compensation terms from a delayed copy of the digital input to yield a predistorted digital input. The TIDAC converts on the predistorted digital input into a fullband analog output that is substantially free of nonlinear distortion.
Claims24
A method of predistorting a digital waveform, the method comprising:
- creating a polyphase nonlinear compensation term representative of a nonlinear response of at least one digital-to-analog converter (DAC) in a time-interleaved digital-to-analog converter (TIDAC) having a number (N) of DACs, wherein at least N−1 filters operate in parallel on the digital waveform, and wherein a switch interleaves outputs of the at least N−1 filters utilizing a processor;
- and
- obtaining a predistorted digital waveform by subtracting the polyphase nonlinear compensation term from a copy of the digital waveform utilizing a summer.
An apparatus for predistorting a digital waveform, the apparatus comprising:
- a processor configured to generate a polyphase nonlinear compensation term representative of a mismatch between a number (N) of digital-to-analog converters (DACs) in a time-interleaved digital-to-analog converter (TIDAC), wherein at least N−1 filters are configured to operate in parallel on the digital waveform, and wherein the processor includes a switch configured to interleave outputs of the at least N−1 filters;
- and
- a summer operably coupled to the processor and configured to obtain a predistorted digital waveform by subtracting the polyphase nonlinear compensation term from a copy of the digital waveform.
An apparatus for predistorting a digital waveform, the apparatus comprising:
- means for creating a polyphase nonlinear compensation term representative of at least one of a nonlinear response of a digital-to-analog converter (DAC) and a mismatch between a number (N) of DACs in a time-interleaved digital-to-analog converter (TIDAC), wherein at least N−1 filters operate in parallel on the digital waveform, and wherein a switch interleaves outputs of the at least N−1 filters;
- and
- means for obtaining a predistorted digital waveform by subtracting the polyphase nonlinear compensation term from a copy of the digital waveform.
Dependencies are inferred from the claim text.