Logarithmic transformer and method of logarithmic transformation

摘要

A logarithmic transformer capable of a reduction in circuit scale. A logarithmic transformation upper bit string generating unit (3) detects a highest order bit of logic "1" out of the bits b_n-1, ..., b₀ of input data B as an active bit. Binary data for indicating the bit position S of the active bit is generated as a logarithmic transformation upper bit string D_UP (d_m-1, ..., d_m-p). Here, based on the number of bits n of the input data B, the number of bits p of the logarithmic transformation upper bit string D_UP (d_m-1, ..., d_m-p) is set for the relationship n = 2^P. A logarithmic transformation lower bit string generating unit (4) determines a bit string of order lower than the bit position S, having a predetermined number q of bits, out of the bits b_n-1, ..., b₀ of the input data B. The resultant bit string makes a logarithmic transformation lower bit string D_LOW (d_m-p-1, ..., d₀). Then, logarithmic transformation data D having a total number of p + q bits is generated with the logarithmic transformation upper bit string D_UP (d_m-1, ..., d_m-p) as the integral part of a logarithmic transformation value resulting from the logarithmic transformation of the input data B and the logarithmic transformation lower bit string D_LOW (d_m-p-1, ..., d₀) as the fractional part of the logarithmic transformation value resulting from the logarithmic transformation of the input data B.