Digital modulation techniques

This document discusses digital modulation techniques used to encode information onto carrier signals for transmission. It explains that modulation involves adding information to a carrier signal by varying the amplitude, frequency, or phase. Specifically, it describes amplitude-shift keying (ASK), which encodes bits as two amplitude levels while keeping frequency constant, as well as frequency-shift keying (FSK) and phase-shift keying (PSK), which encode bits by shifting the frequency or phase of the carrier signal. The document also mentions channel capacity and reasons for choosing different encoding techniques.