Fig.1: NRZ signal (top) and eye diagram (bottom). Pulse amplitude modulation builds upon this concept by encoding data across multiple voltage levels. PAM4 uses four levels. A PAM4 signal can appear ...

(a) Schematic diagram of the pulse-density modulation control of time-variable q(t). When the pulse train of p ( t ; T , w ) is denser, q ( t ) is higher, and vice versa. ( b – e ) Generation of ...