New fast transform based complex transmultiplexer algorithm for QPSK digital multicarrier demodulator application

The complex input-complex output block processing TMUX structure has been suggested as the pertinent structure in the multicarrier demodulation (MCD) function based upon the maxim of overall computational load. A new complex polyphase-FFT TMUX algorithm using two N/2-point complex conjugate fast transform processors with direct application to the SCPC-FDMA QPSK MCD has been presented which, for an N=16 channel MCD functioning at a sampling rate of 9.6 kHz allows a saving of 60% in the number of non-trivial real multiplications required in the transform processors, and gives a reduction of approximately 2% and 4% in the number of real additions and multiplications respectively in the TMUX processing as a whole. The new approach may offer greater flexibility than current block-transform approaches for a VLSI implementation