Pre-distortion for fast power transient waveforms
First Claim
1. A linearizer for a power amplifier, comprising:
- a power detector which provides an instantaneous power signal based on an input signal to the linearizer;
a function generator for generating a set of basis function signals based on the instantaneous power signal;
a set of digital-to-analog converters which change amplitudes of the basis function signals in accordance with a set of corresponding coefficients;
a signal generating circuit which provides an output signal of the linearizer based on the changed amplitudes of the basis function signals;
anda controller, which includes a filter sensitive to a change in the instantaneous power signal and which selects one of a plurality of sets of parameter values based on an output of the filter, each set of parameter values corresponding to a range of signal power, and which derives therefrom the set of corresponding coefficients for the digital-to-analog converters.
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Abstract
An apparatus and a method select and use parameter values for an RF power amplifier linearizer to pre-distort the input signals of a power amplifier, so as to achieve a linear output response in the power amplifier. The apparatus and the method select from a number sets of parameter values, each set of parameter values corresponding to a different output power range of the power amplifier. The set of parameters include a coefficient vector tailored for the particular output power range for that set. The power amplifier input power is repeatedly measured and filtered at various time intervals. The input power measurements may be filtered by a fast attack/slow decay filter, which follows the peaks of the measurements under operation of the fast attack portion of the filter and provides a low variance during operation of the slow decay portion of the filter. The coefficient values for the predistortion linearization of the power amplifier is adapted dynamically, in response to changes in the input power level of the power amplifier. In one embodiment, hysteresis is used to reduce the rate at which the predistortion linearizer hops between two sets of the parameter values. Using the apparatus and the method, good ACLR across a wide range of power amplifier output power is achieved. Such characteristics are particularly advantageous in a system in which waveforms having fast power transients are present.
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Citations
26 Claims
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1. A linearizer for a power amplifier, comprising:
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a power detector which provides an instantaneous power signal based on an input signal to the linearizer; a function generator for generating a set of basis function signals based on the instantaneous power signal; a set of digital-to-analog converters which change amplitudes of the basis function signals in accordance with a set of corresponding coefficients; a signal generating circuit which provides an output signal of the linearizer based on the changed amplitudes of the basis function signals; and a controller, which includes a filter sensitive to a change in the instantaneous power signal and which selects one of a plurality of sets of parameter values based on an output of the filter, each set of parameter values corresponding to a range of signal power, and which derives therefrom the set of corresponding coefficients for the digital-to-analog converters. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method in a linearizer of a power amplifier, comprising:
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detecting an input signal to the linearizer to provide an instantaneous power signal; generating a set of basis function signals based on the instantaneous power signal; providing a set of digital-to-analog converters which change the amplitudes of the basis function signals in accordance with a set of corresponding coefficients; based on the changed amplitudes of the basis function signals, providing as an output signal of the linearizer; and providing a controller, which includes a filter sensitive to a change in the instantaneous power signal and which selects one of a plurality of sets of parameter values based on an output of the filter, each set of parameter values corresponding to a range of signal power, and which derives therefrom the set of corresponding coefficients for the digital-to-analog converters. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification