Patent ID: 8451055

Claim:
A distortion compensating apparatus that performs predistortion by using a look-up table and optimizes the look-up table by using an adaptive algorithm, the apparatus comprising: a storage unit that stores the look-up table including distortion compensation coefficients respectively stored at addresses assigned to the look-up table; a predistortion unit that selects, using a correlation between a plurality of predetermined parameters and a plurality of the assigned addresses, addresses showing the parameters of an input signal based on the correlation from among the assigned addresses, acquires distortion compensation coefficients stored at the selected addresses, and performs the predistortion of the input signal by using the acquired distortion compensation coefficients; an error calculation unit that calculates an error signal by comparing with the input signal a feedback signal that indicates an output of a power amplifier to which a result of the predistortion is inputted; a coefficient calculation unit that calculates distortion compensation coefficients from the error signal and the acquired distortion compensation coefficients by using the adaptive algorithm; a coefficient selection unit that, for each of the selected addresses, selects distortion compensation coefficients as adequate coefficients from among the calculated distortion compensation coefficients according to the error signal; and a coefficient averaging unit that, for each of the selected addresses, calculates an average value of the adequate coefficients and replaces a distortion compensation coefficient stored at a corresponding address in the look-up table with the average value, wherein for each of the selected addresses, the coefficient selection unit calculates an evaluation value from the error signal, determines a region of the evaluation value, and selects, when the evaluation value is within the region, a distortion compensation coefficient calculated from the error signal as one of the adequate coefficients, and wherein the coefficient selection unit stores a relationship between an address in the look-up table and a threshold value defining the region and determines the threshold value based on the selected addresses by using the relationship.