What types of distortions are important in a cable system?
The important distortions are primarily second and third order. Higher order distortions do occur but at normal operating level they usually are small enough to be ignored. Second order distortions are the result of a second order non-linearity. They are formed by one mixing operation and result in products such as A+B, A-B, 2A, 2B. Third order distortions are the result of third order non-linearity and are formed by two mixing operations such as (A)+(A)+(A) or 3A, (A)+(A)+(B), 2A+B, A+B+C. Crossmodulation is a third order distortion. The products do not all have the same amplitude, for example the 2A product in 6 dB lower than the A+B product. For more information on this subject, see MTN-108.
