This paper presents the periodic spectrum transmission for single-carrier frequency-domain equalization (SC-FDE) employing space-time transmit diversity (STTD). The proposed scheme utilizes only even-numbered samples within a time-domain data block to create a periodical spectrum which provides frequency redundancy. Frequency redundancy is used for sub-channel combining before FDE, which alleviates the loss of orthogonality caused by FDE under frequency selective fading channels. Therefore, the proposed scheme has an advantage of enhancing the overall frequency diversity benefit while keeping the space diversity benefit achieved by STTD. Computer simulation results show that the proposed scheme outperforms the typical SC-FDE using full samples over relatively severe frequency selective fading channels when applying 1-bit/sample transmission.