MSB modulation doubles cable TV and FM-SCA capacity

Ultra narrow band modulation (minimum sideband, MSB, modulation) makes it possible to insert a 12 Mb/s digital channel between each of the present analog channels on a cable TV system. A 100 channel analog system then becomes a 200 channel system, with 100 analog and 100 digital channels. This unique phase modulation method has no Bessel sidebands to interfere with adjacent analog channels. The spectrum consists of a single frequency that is inserted in quadrature below the adjacent video channel. All spectral spread is at such low levels that it is considerably below the noise level of the cable system. The presently accepted signal and noise levels for cable TV are easily met. The 12 Mb/s data rate can be increased if necessary to more than 20 Mb/s without ill effect. The method is also useful for FM-SCA (FM supplementary carriers) at very high data rates.