Patent ID: 7693922

Claim:
A method for preprocessing a signal performed on an apparatus with a processing unit comprising the steps of: receiving an input signal I at the processing unit of the apparatus, generating an output signal which is a transformation H −1 .I of said input signal I with respect to the inverse transfer function H −1 of a given transfer function H or an approximation of said transformation, and outputting said output signal as a preprocessed signal from the apparatus, wherein said generating said output signal includes at least one step of iterating, and said iterating comprises the steps of: receiving a preceding intermediate output signal and said input signal, applying a transformation process to said preceding intermediate output signal which causes the preceding intermediate output signal to be completely or approximately transformed according to said given transfer function H to generate a transformed preceding intermediate output signal, subtracting said transformed intermediate output signal from said input signal I to generate an intermediate error signal, and adding said intermediate error signal or a weighted derivative of the intermediate error signal to said preceding intermediate output signal to generate a succeeding intermediate output signal, wherein in non-initial iterations a succeeding intermediate output signal of a preceding iteration is used as said preceding intermediate output signal for a succeeding iteration, in an initial iteration said input signal I is used as said preceding intermediate output signal, and under a certain stop condition, said iterating is stopped with the present succeeding intermediate output signal as said output signal.