An improved double test algorithm in Hadamard transform(HT)domain is proposed in this paper.First

two kick-out conditions in original DTA method are rewritten properly in HT domain.Then

codewords and input vectors in HT domain are properly partitioned based on the result of the preliminary experiment.Finally

by using the better kick-out condition many unmatched codewords can be eliminated.The simulation shows that the search space of the improved algorithm in this paper is reduced to about 14%～17%

and the encoding time is reduced to about 35%～45% compared to the original algorithm.