Patent ID: 7415252

Claim:
A system for forming a predistorted signal from a broadband interpolated baseband signal for a transmit power amplifier having n cascaded branches, comprising: a predistortion unit provided for the first branch of the amplifier, the predistortion unit producing an estimated output signal of the transmit power amplifier, the estimated output signal being formed based on memory effects of the amplifier, the predistortion unit having an input receiving the interpolated baseband signal as an interim predistorted signal; first and second adders, a distortion unit, a predistortion unit, and a digital filter provided for every jth branch of the amplifier where 2≦j≦n, wherein: the first adder has an input to receive the interpolated baseband signal via the distortion unit and an input to receive the output signal from the predistortion unit of the j−1th branch, the first adder having an output producing an error signal that is supplied to the digital filter, the second adder proportionately forms an interim predistorted signal, the second adder having an input to receive the error signal via the digital filter and an input to receive the interim predistorted signal from the j−1th branch, and the predistortion unit receives the interim predistorted signal from the second adder and produces an output signal; and a downstream filer connected to the output of the second adder of the nth branch, the downstream filter producing the predistorted signal.