Application of Multi-Frequency Modulation (MFM) for High-Speed Data Communications to a Voice Frequency Channel.

摘要

Multi-Frequency Modulation (MFM) has been developed at NPS using both differential quadrature-phase-shift-keying (DQPSK) and differential-quadrature-amplitude-modulation (DQAM) encoding formats. Previous applications of these encoding formats were on industry standard computers (PC) over a 16-20 kHz channel. This report discusses the implementation of MFM to a voice frequency channel of 200-3400 Hz, for possible future use with high-speed modems over switched telephone networks. Research and testing for this report included the DQPSK and differential 16-quadrature-amplitude-modulation (D16-QAM) encoding formats implemented on PCs. Experimental results of the implemented MFM signal were comparable to theory with acceptable bit error rates for input signal-to-noise ratios (SNR) of 15 dB and higher.