characteristics of the amplifier 128 are such that as the value of the variable i is reduced the residual distortion at the upper frequency is reduced or the residual distortion at the lower frequency is reduced fig5 illustrates an example of an operation flow executed by the residual distortion analyzer 116 to confirm the characteristics of the amplifier 128 when the characteristics of the amplifier 128 are unknown the operation flow in fig5 is executed before the operation flows in fig4 a 4 b and the like are executed the residual distortion analyzer 116 receives a digital signal which is an output signal from the a d converter 146 s 301 the residual distortion analyzer 116 then performs a fast fourier transform fft on the received output signal s 302 the residual distortion analyzer 116 then calculates the residual distortion of the signal resulting from the fft s 303 in the description below the residual distortion at the lower frequency will be represented as l 1 and the residual distortion at the upper frequency will be represented as u 1 it is assumed here that the initial value of the variable i is for example d 0 and the initial value of the variable j is for example d 0 the residual distortion analyzer 116 assigns i u2212 1 to the variable i s 304 the residual distortion analyzer 116 takes the variable i after the assignment as i 0 and the variable j as j 0 and notifies the dpd unit 112 of i 0 and j 0 the residual distortion analyzer 116 receives an output signal that corresponds to a pre distorted signal calculated by using i 0 and j 0 the notification of which has been sent to the dpd unit 112.