A full digital modem for offset type modulation schemes

This paper proposes a full digital modem employing a reverse-modulation type carrier recovery scheme for offset type modulation schemes. The full digital modem employs a wave forming filter for reverse-modulation of offset type modulated signals to increase the extracted carrier signal-to-noise ratio. The proposed modem achieves both high speed carrier acquisition and low carrier slipping rate simultaneously which other methods cannot achieve. Computer simulation results show that the proposed modem applied to OQPSK systems achieves a low carrier slipping rate performance of less than 1.0×10^-7 event/symbol at an Eb/No of 4 dB with negligible bit error rate degradation. The proposed modem can be implemented in all-digital circuits and suitable for LSI implementation