Signal processing apparatus, digital filter and recording medium

A non-transitory recording medium having recorded therein a program to cause a computer to function as a signal processing apparatus for compensating for a non-linear distortion of a digital signal, comprising:

• an analysis signal generating section that converts the digital signal into an analysis signal of a complex number, using a digital filter;
• and
• a compensation section that generates a compensating signal based on the analysis signal and on a compensation coefficient of a complex number corresponding to the non-linear distortion, and compensates for the non-linear distortion of the digital signal using the compensating signal, wherein
• the digital filter divides data of the digital signal into “n” data sequences, assigns (n*L=k)th data of the digital signal to a k-th data sequence, performs filtering on each of the data sequences using a same filter coefficient, and combines each of the data sequences after the filtering, thereby generating an imaginary number portion of the analysis signal, where “n” is an integer equal to or greater than 2, L=0, 1, . . . , and k=1, 2, . . . ,n.