Metoda Obliczania Gestosci Widmowej Mocy Sygnalow Modulowanych Ciagiem Danych Cyfrowych

The paper deals with spectral analysis of coded signals resulting from encoding and modulation of constant length data words. The modulator is defined as a Moore finite state sequential machine assigning an isochronic sequence of multiparameter output pulses to a string of data words (input pulses). Two cases are considered: (i) when the input strong is a random sequence with independent terms, and (ii) when it is a stationary Markov chain. The parameters of stationary Markov chains of output sequences are found, and, consequently, the closed form formulae for power spectral densities of output signals are established. To illustrate the applicability of the method, simple examples are given: for a code 1B-2B and PAM, and for digital FM. One theoretical limitation of the method is that the set of the shapes of output pulses must be finite.