Abstract :
This paper presents a multicarrier demodulator (MCD) for FDM systems, which is based on the fast Fourier transform (FFT) technique. We show that, without pulse shaping, user´s synchronization errors and Doppler shifts imply the use of weighting functions or guard time on the received symbols. Both techniques, evaluated through computer simulations, lead to a loss in SNR and spectral efficiency. The next step is to study a possible coherent QPSK mode in order to oppose these losses. Because of the small number of symbols per hop, coherent demodulation is not an easy task. We present a demodulation technique, based on a feedback principle, that shows little loss compared to the theoretical QPSK performance and resists high enough Doppler values
Keywords :
Doppler shift; demodulation; demultiplexing; fast Fourier transforms; feedback; frequency division multiplexing; frequency hop communication; microwave links; military communication; quadrature phase shift keying; satellite communication; synchronisation; Doppler shifts; EHF military satellite communication; FDM systems; FFT; MDR frequency hopped satcom system; MDR standard; QPSK performance; SNR; coherent QPSK mode; coherent demodulation; computer simulations; fast Fourier transform; feedback; frequency hopping system; guard time; multicarrier demodulation; multicarrier demodulator; multicarrier demultiplexing; pulse shaping; received symbols; simulation analysis; spectral efficiency; user synchronization errors; weighting functions; Computer errors; Computer simulation; Demodulation; Demultiplexing; Doppler shift; Fast Fourier transforms; Feedback; Frequency synchronization; Pulse shaping methods; Quadrature phase shift keying;
