By Ron D. Katznelson, Ph.D. CTO, Broadband Innovations, Inc.,
This paper addresses the technical requirements and implications for multichannel QAM RF modulators and upconverters and the factors that affect their proposed RF specifications. RF output power levels per channel, adjacent channel noise and broadband noise levels of such a class of multichannel modulators will be discussed. A spectral noise specification mask that is equivalent to that obtained from a combination of multiple identical masks of a standard single channel noise specifications based on power addition will be presented. The power back-off required for maintaining the proposed distortion mask levels as a function of the number of adjacent channels supported by these devices will be presented. A proposed multichannel downstream RF specification standard based on these results will be presented for consideration for a new DOCSIS™ class of high-density RF modulators.