\input zb-basic
\input zb-ioport
\iteman{io-port 04168377}
\itemau{Calderbrank, A.R.; Mazo, J.E.}
\itemti{Baseband line codes via spectral factorization.}
\itemso{IEEE J. Sel. Areas Commun. 7, No.6, 914-928 (1989).}
\itemab
A description is given of a methodology for designing baseband line codes with prescribes spectral nulls in the transmitted spectrum. These codes have the property that the transmitted power is adjustable (with a concomitant change in spectralshape, i.e. null width) and can be made arbitrarily close to the innovations power, while keeping the minimum distance between signal points (or sequences) constant. The essential design step requires the spectral factorization of a certain trigonometric polynomial. The line code that results can easily be used in conjunction with a large class of trellis-coded modulation schemes. Specific baseband codes are constructed using a representation of the general theory that involves a dither variable, which is used to create integer symbols and to minimize the size of the symbol alphabet. Emphasis is on the design of line codes with a double null at 0 frequency using the symbol alphabet $\{\pm 1,\pm 3\}$.
\itemrv{P.Cotae}
\itemcc{}
\itemut{running digital sum; coding gain; linear prediction theory; metric polynomial; baseband line codes; trellis-coded modulation schemes; dither variable}
\itemli{}
\end