a method for calculating frequency offset using arc tangent calculations according to real part and imaginary part input values received externally . the method includes converting arc tangent equations for determining frequency offset into equations to perform log calculations ; calculating frequency offset using linear approximation and the converted log equations ; and dividing the real part input value to bit values of a predetermined size to realize a size similar to that of the imaginary part input value if a range of the frequency offset value to be calculated is small . with the use of the method , hardware area and power consumption may be reduced , and precise frequency offset may be calculated .