Assessing delay distortion effects in data systems

AN ESSENTIAL OBJECTIVE of a pulse transmission system is the preservation of some aspect of the pulse shape at the receiver. Phase characteristics of a system, which can generally be neglected in voice transmission, become important in pulse systems, because the shape of a pulse is influenced greatly by the relative phase of the spectrum components. A quantity frequently used to describe this influence is envelope delay distortion. It is a measure of the relative phase shift experienced by neighboring components of the frequency spectrum, and is equal to the slope of the tangent to the phase curve at any given frequency. The object of this article is to illustrate a method for assessing the effects of delay distortion on data-transmission systems, based on experimental tests.