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US 5,396,190 AGranted
Circuit for compensating for nonlinear distortion in transmit power amplifier
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorTakashi Murata
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AssigneeMitsubishi Denki Kabushiki Kaisha
InventorTakashi Murata
Estimating the term…
A distortion compensating unit is provided which can reduce the time required to converge distortion compensation values into a given value and operate with an improved stability after said convergence. Constants of multipliers in a correcting factor generating circuit are switched from one to another, depending on the time from the start of operation of a distortion compensating circuit or the temperature in a power amplifier. A constant to be switched is selected to be larger than that of the prior art until the convergence is completed and to be smaller than that of the prior art after the convergence has been completed. Thus, the time required to converge the corrected value into a given value can be reduced to less than that of the prior art. In addition, the distortion compensating unit can operate with an improved stability after the convergence.
A distortion compensating unit comprising distortion pre-compensating means having a memory for receiving a base band signal and memory read signal to record and update data used to compensate for the nonlinearity of an amplifier, the distortion pre-compensating means operable to pre-distort the nonlinearity of said amplifier in the opposite direction so that a distortion produced in said amplifier will be offset by said pre-distortion, a modulator responsive to the output of the distortion pre-compensating means to provide a modulated signal to said amplifier, a demodulator for taking out and demodulating part of the output of said amplifier, comparator means for comparing the output of said demodulator with said base band signal, and a correction factor generating circuit for computing a plurality of corrective coefficients to the contents of said memory from the output of said comparator means by switching said corrective coefficients, the corrected contents of said memory being then provided to said base band signal to predistort the nonlinearity of said amplifier.
A distortion compensating unit comprising distortion pre-compensating means having a memory for receiving a base band signal and memory read signal to record and update data used to compensate for the nonlinearity of an amplifier, the distortion pre-compensating means operable to pre-distort the nonlinearity of said amplifier in the opposite direction so that a distortion produced in said amplifier will be offset by said pre-distortion, a modulator responsive to the output of the distortion pre-compensating means to provide a modulated signal to said amplifier, a demodulator for taking out and demodulating part of the output of said amplifier, comparator means for comparing the output of said demodulator with said base band signal, and a correction factor generating circuit for computing a plurality of corrective coefficients to the contents of said memory from the output of said comparator means by switching said corrective coefficients depending on the temperature of said amplifier, the corrected contents of said memory being then provided to said base band signal to pre-distort the nonlinearity of said amplifier.
Dependencies are inferred from the claim text.