ANSI/SCTE 06 2019

Composite Distortion Measurements (CSO & CTB)

Cable systems are traditionally comprised of multiple analog channels with an even frequency spacing between channels. When this channel lineup passes through devices in the cable plant, especially active devices, distortion products are generated which interfere with the analog channels.

With multiple, evenly spaced channels, the second and third order distortion products combine and add at constant frequencies across the band around and on top of the channel frequencies themselves, creating composite second order (CSO) and composite third order (CTB) distortion products.

Having a standard consistent method of measuring the CSO and CTB distortion products allows system operators a method of setting standard performance criteria for the individual components, and vendors a method of validating the performance of their products. A standard method of measurement is critical in determining the distortion of individual components and the end to end performance of the complete cable plant.