All-digital AFSK modem with Viterbi detection for TT&C CubeSat transceiver

Abstract

Audio-Frequency Shift Keying (AFSK) with continuous phase modulation and non-coherent demodulation is widely used on the telecommand channel of the most TT&C transceivers for CubeSat. However, this solution has low efficiency in terms of power. In this paper, a new all-digital AFSK modem is proposed. The demodulator uses the Viterbi algorithm to perform the maximum likelihood sequence detection (MLSD) and gives an expressive gain when compared to non-coherent detection. Original mathematical analyzes are presented to explain the proposed system. Some performance results, determined via computational simulation, are presented and discussed.