Crest factor reduction for use in a multiband transmitter
First Claim
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1. A method for crest factor reduction in a multiband transmitter, comprising:
- obtaining baseband signals;
combining the baseband signals to provide a superposed signal;
clipping the superposed signal to limit magnitude of the superposed signal;
obtaining a clipping error caused by the clipping;
least squares projecting of the clipping error into sub-band components of the baseband signals to provide projected error components;
filtering the projected error components;
upconverting the projected error components to frequency bands associated with the baseband signals; and
adding the projected error components filtered and upconverted to the superposed signal.
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Abstract
Crest factor reduction in a multiband transmitter is described. Component signals (xi[n]) are respectively obtained from constituent signals. The component signals (xi[n]) are respectively associated with sub-bands. A superposed signal associated with the component signals (xi[n]) is clipped to obtain a clipping noise error signal. The clipping noise error signal is applied to the component signals (xi[n]) using a least squares estimation to project clipping noise error onto the sub-bands.
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Citations
20 Claims
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1. A method for crest factor reduction in a multiband transmitter, comprising:
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obtaining baseband signals; combining the baseband signals to provide a superposed signal; clipping the superposed signal to limit magnitude of the superposed signal; obtaining a clipping error caused by the clipping; least squares projecting of the clipping error into sub-band components of the baseband signals to provide projected error components; filtering the projected error components; upconverting the projected error components to frequency bands associated with the baseband signals; and adding the projected error components filtered and upconverted to the superposed signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for crest factor reduction in a multiband transmitter, comprising:
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obtaining a clipped version of a superposed signal; obtaining an error component associated with the clipped version of the superposed signal; projecting the error component into sub-bands using a least squares estimation to provide sub-band errors; spectrally shaping the sub-band errors to comply with an adjacent channel leakage ratio of the multiband transmitter; frequency modulating resultant noise from the shaping of the sub-band errors to corresponding sub-band frequencies to provide error components; and combining the error components spectrally shaped and frequency modulated with the superposed signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. An integrated circuit for crest factor reduction in a multiband transmitter, comprising:
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modulators for receiving constituent signals and frequency shifted signals, the constituent signals associated with a signal space, the modulators configured to provide component signals respectively associated with the constituent signals, the component signals occupying respective signal subspaces of the signal space; a first combiner coupled to receive the component signals and configured to combine the component signals to provide a superposed signal; a clipping circuit coupled to receive the superposed signal and configured to provide a clipped superposed signal; a second combiner coupled to receive and to combine the superposed signal with the clipped superposed signal to generate a clipping error signal; a least squares fit circuit coupled to receive the component signals and the clipping error signal, the least squares fit circuit configured to project clipping noise error associated with the clipping error signal onto the signal subspaces of the component signals; a bandpass filtering circuit coupled to receive the component signals with the clipping noise error projected thereon and configured to provide noise-shaped subspace error signals respectively responsive to bandpass filtered versions of the component signals to remove at least a portion of the clipping noise error respectively projected thereon; a third combiner coupled to receive the noise-shaped subspace error signals and configured to combine the noise-shaped subspace error signals to provide a noise-shaped space error signal; and a fourth combiner coupled to receive the superposed signal and the noise-shaped space error signal at least approximately phase aligned and configured to combine the superposed signal and the noise-shaped error signal to provide a crest factor adjusted version of the superposed signal. - View Dependent Claims (18, 19, 20)
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Specification