Spectral-energy dispersal in digital communication-satellite systems

Communication-satellite systems employing analogue or digital modulation techniques generally require some means of artificially dispersing their spectra to reduce interference to other services sharing the same frequency bands. In digital systems, the dispersal can be obtained by the modulo-2 addition of a pseudorandom sequence to the information signal. Expressions have been derived for the maximum spectral power in the signals of time-division multiple-access systems employing p.s.k. modulation and using this means of dispersal. The spectral density due to the preambles in such signals is also determined. An example of the practical application of the expressions is given.