Maximum Bandwidth Utilization Demodulator

In narrow-band transmission of television or radar over telephone lines it is necessary to use a carrier system to avoid phase distortion normally present at the lower end of the transmission band. Using ordinary modulation and demodulation techniques, the usable video bandwidth is limited to one-half the carrier frequency. In the limiting case in which the carrier is placed at the extreme upper end of the band, thin is one-half the total available bandwidth.A new modulation-demodulation system has been developed which is basically amplitude modulation but which is not subject to the normal two-to-one limitation. Using this system, it is possible to use a video frequency of as much as nine-tenths that of the carrier. For example, one may use a video frequency of 3.2 kc on a 3.5-kc carrier.