A couple years ago I experimented with the Coherent FDM modem using Newman Phases instead of the spacing scheme of the original. It turned out there was no advantage. The increasing linear spaced carriers reduced the crest-factor the same as Newman Phases.
For the 700D we of course use an IDFT and DFT, and the carrier spacing is constant. I could not figure out how to change the phase of each carrier in a simple way. What would help is if each carrier was sent with a different starting phase. The formula for Newman Phases is: delta-sub-k = (pi * ((k - 1)^2)) / N Where k is the carrier (numbered 1 to N), N is the total number of carriers, and delta-sub-k is the phase of the kth carrier. The starting phase is 0, the second at pi/N radians, the third at 4pi/N radians, etc. Theoretically, the crest-factor can be limited to about 4.6 dB using Newman Phases.
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