Filter coefficient calculation method and filter coefficient calculation unit

A filter coefficient calculation unit comprising:

• a weight coefficient calculation unit that calculates a first filter function having (2n+1) rows and (2n+1) columns (n is an integer) according to a set value that is externally input;
• an error calculation unit that calculates an error between a total sum of values included in the first filter function and an ideal value of the total sum;
• an odd error correction unit that supplies an odd error included in the error to a first origin coefficient that is located at a center of the first filter function as a first correction value if the error is an odd number, so as to correct the first origin coefficient;
• and
• an even error correction unit that supplies an even error to one of the first origin coefficient and a coefficient pair that is located symmetrically with respect to a point of the first origin coefficient as a second correction value, the even error being the error except the odd error, so as to correct the error of the first filter function.