Multichannel M-Ary Frequency-Shift-Keying Block Demodulator Implementation

摘要

The Military Satellite Communications (MILSATCOM) group at Defence ResearchEstablishment Ottawa (DREO) is performing in-house satellite communications uplink synchronization experiments. A critical part of the experiment is the block demodulation of the multi-channel frequency-hopped waveform. This report analyses the Fast Fourier transform (FFT)-based demodulator implemented by Royal Military College (RMC) Kingston. This system is capable of demodulating a 32 channel, 8-ary frequency-shift-keying (FSK) waveform. The implementation consists of analog-to-digital (A/D) conversion, FFT computation, and high speed input/output (I/O) interface processes using commercial off-the-shelf boards. A description of each of the boards is presented. The operational data flow of the system is examined. For the software implementation, a decimation-in-time approach is used in the digital signal processing (DSP) board to compute the discrete Fourier transform (DFT). A brief description of decimation-in-time algorithms is included. Key components of the assembly language program are outlined. A user's guide detailing the setup requirements for proper operation of the system is included with those required for the DREO application. Steps required for modification to the software are briefly discussed.