Patent ID: 8379708

Claim:
A method for digitally filtering a signal comprising: sampling a signal and representing the signal discretely by a plurality of reference symbols with different phases and amplitudes; sampling more finely between said plurality of discretely represented reference symbols to prepare a plurality of interpolate symbols consisting of symbols with different phases and amplitudes as discrete representations; giving a sequence pattern that represents positive and negative direction transitions that continue over a predetermined number from a certain reference symbol to an adjoining reference symbol; finding one or more interpolate symbols that meet conditions of a predetermined frequency spectrum and a predetermined amplitude with reference to the given sequence pattern; storing the found sequence pattern and a phase value and an amplitude value corresponding to the found one or more interpolate symbols as a lookup table in a memory; receiving a real signal as an input and converting the signal into said sequence pattern with reference to the reference symbols; looking up whether a sequence pattern that matches the sequence patterns stored in said memory is among the converted sequences; and if a matched sequence pattern is detected by the looking up, reading out the phase value and the amplitude value corresponding to one or more interpolate symbols that constitute the sequence pattern from said memory, and providing the real signal as a digitally filtered signal.