Sideband Modulations

• Reduction in transmitted power • Reduction in Bandwidth (B)• Reduction in kTB• Sideband modulators are more complex• Sideband demodulators can be extremely complex

Alphabet Soup

__SB - __C

S : SingleD : DoubleV : Vestigial

F : FullR : ReducedS : Suppressed

(Side Band)(Carrier)

Vestigial Sideband

x e(t)

(Vestigial Side Band)1

a(t)

cos(ct)

+

+

VSBFilter

c

c

• Less Transmitted Bandwidth

• Most of lower sideband power eliminated

• Less Carrier Power

VSB Receiver IF Compensation

VSB Compensation Filter de-emphasizes the additional low frequency content introduced by the LSB

IF

Low Frequency Content in LSB

DSB - SC

x e(t)

1

a(t)

cos(ct)

+

+

c

• Same Transmitted Bandwidth

• Zero Carrier Power• Generate with Double

balanced Mixer (no offset)

c c

Low Pass Filter

MC1596 Analog Multiplier

G +G -

G+ = kS+ , and G- = kS-

-Vo(+) = (C+ - C-)G-

+ (C- - C+)G+

-Vo(-) = (C+ - C-)G+

+ (C- - C+)G-

Vo(+) - Vo(-)= -2[(C+ - C-)G-

+ (C- - C+)G+]=2(C- - C+)(G+ - G-)

But C- = - C+ , S- = - S+

Vo(+) - Vo(-) = 8kS+C+