Bandwidth efficient transmultiplexers. I. Synthesis

Develops a set of conditions which allow bandwidth efficient transmultiplexers to be synthesized. The synthesis procedure is based upon a generalized impulse response for the combining (modulating) and separation (demodulating) filters. In particular, the combining and separation filters are bandpass versions of one of two low-pass prototypes and are configured to cancel crosstalk by exploiting relationships between the center frequencies, delays, and phases in their impulse response. Based on the derived conditions, five different transmultiplexers are synthesized. Three of them implement multicarrier quadrature amplitude modulation (QAM). The other two accomplish multicarrier vestigial sideband modulation (VSB). Intersymbol interference is eliminated by appropriately designing the prototypes. The two band case is treated as a special case. For this case, the extra flexibility in choosing the center frequencies leads to the synthesis of additional transmultiplexers