LTI systems cannot create new frequency components from their input signals

Evidence

An LTI system also guarantees that it does not create any new frequency components that do not exist in the input signal, i.e., it does not generate non-linear distortion. Thus, a pure tone (a sinusoidal signal) remains a pure tone when propagating through an LTI system. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 350

Categorization

• DEFINE: Defines the key distinguishing property of LTI systems in a crisp, load-bearing way.