Application of Multi-Frequency Modulation (MFM) to facsimile machines

Abstract

Multi-Frequency Modulation (MFM) has been developed at NPS using both differential quadrature-amplitude-modulation (DQAM) and differential quadrature- phase-shift-keying (DQPSK) encoding formats. This report discusses the use of each of these formats in transmitting a facsimile encoded message over a voice frequency channel. The satisfactory transmission and receipt of facsimile messages was achieved using both DQPSK and D16-QAM encoding formats. Research and testing for this report included the use of variable facsimile transmission rates in an attempt to optimize MFM operating parameters. Experimental results revealed a higher error rate when decoding messages contained similar contiguous characters.