Patent ID: 8421533

Claim:
An adaptive digital predistortion device, comprising: a predistortion unit for retrieving a predistortion parameter from a look-up table based on an input signal to be amplified by an amplifier, predistorting the input signal according to the predistortion parameter to generate a predistorted signal to be amplified by the amplifier; a cost function generation unit for generating a cost function based on an output signal of the amplifier; a fixed segment point determination unit for determining a fixed segment point; an update unit for updating parameters (u 1 , u 2 , k a ) according to the cost function to update the look-up table based on the updated parameters (u 1 , u 2 , k a ), wherein k a is an adaptive segment point, u 1 is a slope of a straight line on one side of the adaptive segment point k a , and u 2 is a slope of a straight line on another side of the adaptive segment point k a ; and for updating parameters (v 1 , v 2 ) according to the cost function to update the look-up table based on the updated parameters (v 1 , v 2 ) and the fixed segment point, wherein v 1 is a slope of a straight line on one side of the fixed segment point, and v 2 is a slope of a straight line on another side of the fixed segment point, wherein the update unit updates the look-up table based on the updated parameters (u 1 , u 2 , k a ) by: L ⁡ ( k ) = { u 1 × ( L ′ ⁡ ( k ) - L ′ ⁡ ( 0 ) ) + L ′ ⁡ ( 0 ) k ≤ k a u 2 × ( L ′ ⁡ ( k ) - L ′ ⁡ ( k a ) ) + L ′ ⁡ ( k a ) k > k a , wherein, L′(●) is a look-up table before updating, L(●) is the updated look-up table, and k is an index of the look-up table, and wherein the update unit updates the look-up table based on the updated parameters (v 1 , v 2 ) and the fixed segment point by: L ⁡ ( k ) = { v 1 × ( L ′ ⁡ ( k ) - L ′ ⁡ ( k b ) ) + L ′ ⁡ ( k b ) k ≤ k b v 2 × ( L ′ ⁡ ( k ) - L ′ ⁡ ( k b ) ) + L ′ ⁡ ( k b ) k > k b wherein, k b is the fixed segment point, L′(●) is a look-up table before updating. L(●) is the updated look-up table, and k is an index of the look-up table.