Television Detail and Selective-Sideband Transmission

Recently selective-sideband transmission has been adopted in this country in order to increase the picture detail which can be transmitted in a frequency channel of given width. The present analysis is an examination of the theoretical justification for this practice. The effect of various degrees of unequal-sideband transmission on typical television signals is calculated by Fourier integral analysis. The conclusions reached are as follows: (1) For small percentages of modulation and small changes in the percentage of modulation selective-sideband transmission is equivalent to double-sideband transmission of twice the frequency pass band. (2) For large changes in the percentage of modulation, selective-sideband transmission is equivalent to double-sideband transmission of twice the frequency pass band for the reproduction of symmetrical fine detail. However, at the edges of patterns where there is a great change of visual intensity, selective-sideband transmission introduces more or less false detail, not present in the original signal. The extent of this false detail increases with the sharpness of the rise of the frequency characteristic at the edge of the transmission band where the carrier is located.