A spreading code generating device for a Code Division Multiple Access (CDMA) communication system is disclosed. The device comprises a PN (Pseudo-random Noise) code sequence generator for generating PNi and PNq sequences; an orthogonal code generator for generating first and second orthogonal codes (OC1, OC2) which perform Differential Phase Shift Keying (DPSK) state transitions at intervals of at least two chips; and a spreading code generator for generating spreading codes Ci and Cq by mixing the PNi and PNq code sequences with the first and second orthogonal codes (OC1, OC2) such that a present phase of the spreading codes Ci and Cq alternately makes Quadrature Phase Shift Keying (QPSK) and DPSK state transitions with respect to a previous phase of the spreading codes Ci and Cq.
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