Patent ID: 8862062

Claim:
A radio apparatus for performing radio communication by the use of a plurality of antennas, the apparatus comprising: a subtraction section which subtracts from a received signal point a replica obtained by reflecting an influence of a propagation path state in a likely transmitted signal point; and a calculation section which calculates a metric for the received signal point and the replica from a value calculated by the subtraction section by the use of a linear interpolation formula obtained by separating a quadratic function at a power of 2; wherein: the linear interpolation formula is given by 2 n-1 {|x|+ 2(| x|− 2 n-1 )} where x is the value calculated by the subtraction section and n is a number of digits of the x; and the calculation section includes: an absolute value calculator which calculates |x| of the x; a detector which detects the n from the |x|; an extractor which extracts lowest (n−1) bits from the |x| and which outputs (|x|−2 n-1 ); a first shifter which performs a bit shift on the (|x|−2 n-1 ) and which outputs 2(|x|−2 n-1 ); an adder which adds the |x| and the 2(|x|−2 n-1 ) to calculate {|x|+2(|x|−2 n-1 )}; and a second shifter which performs a bit shift on the {|x|+2(|x|−2 n-1 )} and which outputs 2 n-1 {|x|+2(|x|−2 n-1 )}.