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For an nt transmit, nr receive antenna system (nt × nr system), a full-rate space time block code (STBC) transmits min (nt, nr) complex symbols per channel use. In this paper, a scheme to obtain a full-rate STBC for 4 transmit antennas and any nr, with reduced ML-decoding complexity is presented. The weight matrices of the proposed STBC are obtained from the unitary matrix representations of a Clifford Algebra. By puncturing the symbols of the STBC, full rate designs can be obtained for nr <; 4. For any value of nr, the proposed design offers the least ML-decoding complexity among known codes. The proposed design is comparable in error performance to the well known Perfect code for 4 transmit antennas while offering lower ML-decoding complexity. Further, when nr <; 4, the proposed design has higher ergodic capacity than the punctured Perfect code. Simulation results which corroborate these claims are presented.