Chapter 3. Amplitude Modulation

Start with the sinusoidal modulating wave. Single-Sideband Modulation 2

Generalize (3.17) to periodic message signals Single-Sideband Modulation 3

4

5

SSB Modulation 6 Frequency discrimination method

SSB Modulation 7 Phase discrimination method

SSB Modulation 8 Frequency translation

Vestigial Sideband Modulation 9 Motivation –SSB works well for a message signal with an energy gap centered around zero frequency. –However, the spectra of wideband signals contain significant low frequencies. –DSB-SC requires a transmission bandwidth equal to twice the message bandwidth. Vestigial sideband (VSB) modulation –Instead of completely removing a sideband, a trace of vestige of that sideband is transmitted, the name vestigial sideband. –Instead of transmitting the other sideband in full, almost the whole of this second band is also transmitted.

VSB Filter 10 DSB-SC SSB VSB

VSB Modulator 11

Example: Sinusoidal VSB 12

Coherent Detection of VSB 13

Baseband Representation of Modulated Waves 14

Baseband Representation of Modulated Waves 15

Baseband Representation of Modulated Waves 16

Baseband Representation of Bandpass Filters 17

Baseband Representation of Bandpass Filters 18