for example the p 1 value is set as pt 1 j j 1 n the p 2 value is set as pt 2 j j 1 n and the gi value is set as git j 1 m m is the length of gi the average of p 1 and p 2 is expressed by the following equation on the other hand the average of p 1 p 2 and gi is expressed by the following equation the gi is added to the average and thereby the s n ratio is improved therefore the accuracy of the transmission channel response estimation value is also enhanced in the embodiment the average corresponding to the length of gi i e m averages is taken in this case the average including gi may be less than m averages considering synchronization error and the influence of delay wave in multi path the smoothing circuit 18 will be detailedly explained below with reference to fig4 as depicted in fig4 the smoothing circuit 18 is composed of three registers 181 1 to 181 3 amplitude measuring circuits 182 1 to 182 3 186 dividers 183 1 to 183 3 187 and multiplier 188 the amplitude measuring circuits 182 1 to 182 3 and 186 calculates the amplitude of vector value the dividers 183 1 to 183 3 and 187 are used for dividing each vector into unit vector the vector combining circuit 184 combines each unit vector the average.