Power amplifier pre-distortion
First Claim
1. A training method for a power amplifier pre-distorter formed by a FIR filter structure, wherein the FIR filter structure includes an individual look-up table for each filter tap, the method comprising:
- selecting, from each filter tap of the individual look-up table, a filter coefficient that depends on an amplitude of a corresponding complex signal value to be multiplied by the filter tap;
determining a first estimate of a first look-up table assigned to a first filter tap, assuming a second look-up table assigned to a second filter tap is set to predetermined table values; and
determining a second estimate of the second look-up table assuming the first look-up table is set to the determined first estimate,wherein each look-up table represents a discretized polynomial in a variable representing the signal amplitude of an input signal to the FIR filter structure, andwherein the filter coefficient selected from the look-up table corresponding to each filter tap is independent of complex signal values to be multiplied by other filter taps.
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Abstract
A power amplifier pre-distorter is formed by a FIR filter structure which includes an individual look-up table for each filter tap, where each look-up table represents a sampled polynomial in a variable representing signal amplitude, and means for selecting, from each filter tap look-up table, a filter coefficient that depends on the amplitude of a corresponding complex signal value to be multiplied by the filter tap. A training method for such a pre-distorter determines (S1) a first estimate of a first look-up table assigned to a first filter tap, assuming a second look-up table assigned to a second filter tap is set to predetermined table values. Thereafter the method determines (S2) a second estimate of the second look-up table, assuming the first look-up table is set to the determined first estimate. If deemed necessary, the method includes the further steps (a) refining (S3) the first estimate refined, assuming the second look-up table is set to the latest determined second estimate, and (b) refining (S4) the second estimate, assuming the first look-up table is set to the latest determined first estimate. Steps (a) and (b) may be repeated (S5) until convergence is reached.
26 Citations
14 Claims
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1. A training method for a power amplifier pre-distorter formed by a FIR filter structure, wherein the FIR filter structure includes an individual look-up table for each filter tap, the method comprising:
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selecting, from each filter tap of the individual look-up table, a filter coefficient that depends on an amplitude of a corresponding complex signal value to be multiplied by the filter tap; determining a first estimate of a first look-up table assigned to a first filter tap, assuming a second look-up table assigned to a second filter tap is set to predetermined table values; and determining a second estimate of the second look-up table assuming the first look-up table is set to the determined first estimate, wherein each look-up table represents a discretized polynomial in a variable representing the signal amplitude of an input signal to the FIR filter structure, and wherein the filter coefficient selected from the look-up table corresponding to each filter tap is independent of complex signal values to be multiplied by other filter taps. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A base station including a power amplifier pre-distorter formed by a FIR filter structure including:
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an individual look-up table for each filter tap, each of the individual look-up table representing a discretized polynomial in a variable representing signal amplitude of an input signal to the FIR filter structure; and means for selecting, from each filter tap look-up table, a filter coefficient that depends on the amplitude of a corresponding complex signal value to be multiplied by the filter tap, wherein the filter coefficient selected from the look-up table corresponding to each filter tap is independent of complex signal values to be multiplied by other filter taps, and wherein said base station further includes a pre-distorter trainer including; means for determining a first estimate of a first look-up table assigned to a first filter tap, assuming a second look-up table assigned to a second filter tap is set to predetermined table values; and means for determining a second estimate of the second look-up table, assuming the first look-up table is set to the determined first estimate. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification