Showing papers by "Hiroyoshi Ishikawa published in 2012"

Distortion compensation device, transmitter, and distortion compensation method

Abstract: A distortion compensation device includes a distortion compensator that predistorts an input signal based on delay signals and distortion compensation coefficients corresponding to the respective delay signals obtained by applying different amounts of delay to the input signal, a calculator that calculates an error signal based on the predistorted input signal and an output signal from an amplifier that amplifies the predistorted input signal, a calculator that calculates prospective distortion compensation coefficients for updating the distortion compensation coefficients, based on the error signal, a saturation processor that performs saturation processing for bringing, when the prospective distortion compensation coefficients do not fall into a preset range, the prospective distortion compensation coefficients into the preset range, and a controller that controls the updating of the distortion compensation coefficients based on pieces of coefficient saturation information indicating whether the saturation processing is performed on the prospective distortion compensation coefficients.

Transmitter and distortion compensating method

Abstract: A transmitter, when the power changes at a certain timing, adjusts the gain for the transmission signal before the application of the distortion compensation process correspondingly to the amplitude of the transmission signal at the certain timing based on the average of the power of a transmission signal before application of the distortion compensation process, obtains a distortion compensation coefficient corresponding to the value of the power of the adjusted transmission signal from the LUT, applies the distortion compensation process to the transmission signal using the obtained distortion compensation coefficient, calculates an update for a distortion compensation coefficient corresponding to the obtained distortion compensation coefficient and stored in the LUT based on an error between the power of the transmission signal amplified by an amplifier and the power of the transmission signal before the application of the distortion compensation process, and updates the LUT using the calculated update.

Distortion compensation apparatus, transmitter, and distortion compensation method

Abstract: A distortion compensation apparatus includes an amplifying unit, a plurality of distortion compensation coefficient storage units, a first address generating unit, a second address generating unit, and a distortion compensating unit. The amplifying unit amplifies an input signal. A plurality of distortion compensation coefficient storage units store the distortion compensation coefficients for compensating for the distortion of the amplifying unit by being associated with two different addresses. The first address generating unit generates a first address based on the current input signal. The second address generating unit generates a second address different from the first address based on the previous input signal. The distortion compensating unit obtains the distortion compensation coefficient corresponding to a combination of the first and second addresses from each of the distortion compensation coefficient storage units and performs a pre-distortion processing for the current input signal to the amplifying unit using the obtained distortion compensation coefficient.

Power amplification device, distortion compensation coefficient updating method for the same, and transmission apparatus

Abstract: PROBLEM TO BE SOLVED: To provide a power amplification device that simply computes distortion compensation coefficients in a lookup table.SOLUTION: The power amplification device has an amplifier and a distortion compensation section for performing a distortion compensation process of applying beforehand an inverse characteristic of an input-to-output characteristic of the amplifier to a transmission signal, and inputs an output signal of the distortion compensation section into the amplifier to amplify it. The distortion compensation section has: a coefficient storage section storing a series distortion compensation system of distortion compensation coefficients; and a coefficient updating section calculating an error between a signal resulting from the distortion compensation process of a feedback signal of an output signal of the amplifier by using a distortion compensation coefficient read out from the coefficient storage section and the output signal of the distortion compensation section, calculating an update value of the distortion compensation coefficient in the coefficient storage section so as to converge the error, and updating the distortion compensation coefficient in the coefficient storage section with the update value.

Distortion compensation device and distortion compensating method

Abstract: A distortion compensation device which reduces a distortion of an amplifier which is added to an output signal of the amplifier, the distortion compensation device including: a plurality of distortion compensation coefficient storage circuits which stores a plurality of distortion compensation coefficients and outputs the distortion compensation coefficients according to an amplitude of an input signal of the amplifier, a distortion compensating processing circuit which adds the distortion compensation coefficient output from each of the plurality of distortion compensation coefficient storage circuits to the input signal of the amplifier, and a distortion compensation coefficient updating circuit which performs weighting processing on the distortion compensation coefficient output from each of the plurality of distortion compensation coefficient storage circuits to reduce the distortion compensation coefficient and which calculates an update value of the distortion compensation coefficient by using the distortion compensation coefficient which is subjected to the weighting processing.

Distortion compensation device, distortion compensation method, and radio transmitter

Abstract: A distortion compensation device includes: a frequency-characteristic adding unit configured to add a frequency characteristic to an error signal to generate an added error signal, the error signal being a difference between an input signal input to an amplifier and an output signal output from the amplifier; a distortion-compensation-coefficient updating unit configured to update a distortion compensation coefficient for compensating for a distortion characteristic of the amplifier based on the added error signal; and a distortion compensation unit configured to perform distortion compensation on the input signal using the updated distortion compensation coefficient

Power amplification device, transmitter, and power amplification control method

Abstract: A power amplifier amplifies a signal. An error signal calculating unit calculates an error signal in accordance with an input signal and an output from the power amplifier. A distortion compensation unit performs predistortion on the input signal by using distortion compensation coefficients that are generated in accordance with a plurality of delay signals obtained by giving different amounts of delay to the input signal and by using an error signal and outputs the input signal subjected to the predistortion to the signal amplifying unit. A tap interval control unit controls the delay intervals of the delay signals that are used for the predistortion performed by the distortion compensation unit in accordance with signal correlation information calculated from the input signal.