Adaptive controller for linearization of transmitter with impairments
First Claim
1. A controller for a transmitter comprising:
- a first adaptive controller controlling a gain regulator;
a second adaptive controller controlling a predistortion block and cascaded with the transmitter; and
means for estimating an average closed-loop system gain to provide phase normalized feedback signals for estimation of transmitter nonlinearity, wherein the first and second adaptive controllers are separate, and operate independently wherein normalization of the feedback signals with respect to the input signals is performed for average signal values, and wherein a frequency of consecutive closed-loop gain re-estimation is approximately more than two decades larger than a cut-off frequency of the second adaptive controller.
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Accused Products
Abstract
An adaptive controller for linearization of transmitters using predistortion of the input signal has reduced sensitivity to impairments such as gain variation, phase noise or modulation/demodulation frequency instability by linearizing an adaptively normalized gain provided through a separate estimation and cancellation of linear gain variations. Values of a nonlinear and a linear gain blocks, cascaded with the linearized transmitter and called respectively a predistortion block and a gain regulation block, are independently adjusted by two different adaptive controllers. In one embodiment, four banks of real gain elements compose the predistortion block and realize an arbitrary step-wise approximation of a generalized 2×2 transmit gain matrix of nonlinear functions. In a further embodiment cancellation of a DC level bias multi-channel impairment is provided by an adaptively adjusted signal adder inserted in the transmit chain between the predistortion block and the linearized transmitter.
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Citations
17 Claims
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1. A controller for a transmitter comprising:
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a first adaptive controller controlling a gain regulator; a second adaptive controller controlling a predistortion block and cascaded with the transmitter; and means for estimating an average closed-loop system gain to provide phase normalized feedback signals for estimation of transmitter nonlinearity, wherein the first and second adaptive controllers are separate, and operate independently wherein normalization of the feedback signals with respect to the input signals is performed for average signal values, and wherein a frequency of consecutive closed-loop gain re-estimation is approximately more than two decades larger than a cut-off frequency of the second adaptive controller. - View Dependent Claims (2)
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3. An architecture for controlling the gain of a transmitter, the architecture comprising:
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an adaptive loop coupled to the transmitter, the adaptive loop having a forward branch that propagates an input signal, and a feedback branch that propagates a transmitter output signal; a linear receiver that converts the transmitter output signal; a predistortion block providing nonlinear amplification of the input signal; a gain regulation block providing linear scaling by a complex number of the amplified input signal or a signal in the feedback branch of the adaptive loop; an adaptive predistortion controller that estimates normalized nonlinearity of the adaptive loop and controls the predistortion block; an adaptive gain controller that estimates linear gain and controls the gain regulation block; and a time-division multiplexer synchronizing time-slots for adaptation of the predistortion block and of the gain regulation block. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An adaptive loop coupled to a transmitter having an input and an output, the adaptive loop comprising:
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a linear receiver that converts a transmitter output signal; a predistortion block providing nonlinear amplification of an input signal to be amplified by the transmitter; a gain regulation block providing linear scaling by a complex number of the amplified input signal, and cascaded with the transmitter; an adaptive predistortion controller that estimates normalized nonlinearity of the adaptive loop and controls the predistortion block; an adaptive gain controller that estimates normalized linear gain of the adaptive loop and controls the gain regulation block; and a time-division multiplexer that synchronizes time-slots for independent operation of the predistortion block and predistortion controller, and for the gain block and gain controller. - View Dependent Claims (17)
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Specification