Test: VSBSC (Vestigial Sideband Suppressed Carrier) - Electronics and Communication Engineering (ECE) MCQ

VSB (vestigial sideband) transmission transmits one sideband fully and the other sideband partially thus, reducing the bandwidth requirement.

The spectrum of a vestigial sideband is as shown:

Vestigial Sideband Modulation (VSB) is used for video modulation in TV transmission due to the following reasons :

• Video signal exhibits a large bandwidth and significant low-frequency content which suggests the use of VSB.  
• VSB (vestigial sideband) transmission transmits one sideband fully and the other sideband partially thus, reducing the bandwidth requirement.
• The circuitry for demodulation in the receiver should be simple and therefore cheap. VSB demodulation uses simple envelope detection.

Concept:

Vestigial Sideband Modulation is a type of amplitude modulation where a part of the signal called vestige is modulated, along with one sideband. The spectrum requirement is between DSB-SC and SSB (less than DSB-SC and more than SSB) (Statement 1 is true)
Vestigial Sideband Modulation (VSB) is used for video modulation in TV transmission due to the following reasons:

• A workable compromise between the spectrum-conserving characteristics of single-sideband modulation and the demodulation simplicity of double-sideband amplitude modulation is found in the vestigial-sideband modulation.
• Video signal exhibits a large bandwidth and significant low-frequency content which suggests the use of VSB.  

The spectrum of a vestigial sideband is as shown:

Concept:
VSB modulation is the process where a part of a signal called vestige is modulated along with one of the sidebands.
A VSB signal is plotted as shown in the following figure:

A guard band is a very small frequency width used to avoid interference.
The mathematical representation of the VSB wave is:

V_m, q = Quardature component of V_m.
f_c = Carrier frequency

Power relation in VSB wave:

F = represents a fraction
K = modulation index

Calculation:
Given that:
P_VSB = 0.625, K = 60% = 0.6, F = 25% = 0.25
PC = ?
Then:

Option (2) correct.

VSB (vestigial sideband) transmission transmits one sideband fully and the other sideband partially thus, reducing the bandwidth requirement.
Vestigial Sideband Modulation (VSB) is used for video modulation in TV transmission due to the following reasons:

• Video signal exhibits a large bandwidth and significant low-frequency content which suggests the use of VSB.  
• VSB (vestigial sideband) transmission transmits one sideband fully and the other sideband partially thus, reducing the bandwidth requirement.
• The circuitry for demodulation in the receiver should be simple and therefore cheap. VSB demodulation uses simple envelope detection.
   

The spectrum of a vestigial sideband is as shown:

Concept:
VSB (vestigial sideband) transmission transmits one sideband fully and the other sideband partially thus, reducing the bandwidth requirement.
The spectrum of a vestigial sideband is as shown:

Analysis:
xDSB(t) = m(t) cos ω_ct
= [a₁ cos ω₁t + a₂ cos ω₂t] cos ω_ct
= a₁ cos ω₁t cos ω_ct + a₂ cos ω₂t cos ω_ct
= a₁/2 [cos (ω_c - ω₁)t + cos (ω_c + ω₁)t] + a₂/2 [cos (ω_c - ω₂)t + cos (ω_c - ω₂)t
so, these are the sinusoids that passes through H(ω) and are having gains
0.25, 0.75, 0, 1
∴ xDSB(t) = (a1/8) cos(ω_c - ω₁)t + (3a₁/8) cos(ω_c + ω₁)t + 0 + (a₂/2) cos(ω_c + ω₂)t

In TV Transmission the use of FM is made for Audio transmission and AM for Video transmission.
Vestigial Sideband modulation (VSB) is used for video modulation in TV transmission due to the following reasons :

• Video signal exhibits a large bandwidth and significant low-frequency content which suggests the use of VSB.  
• VSB (vestigial side band) transmission transmits one side band fully and the other side band partially thus, reducing the bandwidth requirement.
• The circuitry for demodulation in the receiver should be simple and therefore cheap. VSB demodulation uses a simple envelope detection.

For narrow and wide bands frequency modulation, modulation index is respectively smaller and greater than 1. When bandwidth is considered it can be approximated to AM.

In TV Transmission the use of FM is made for Audio transmission and AM for Video transmission.
Vestigial Sideband Modulation (VSB) is used for video modulation in TV transmission due to the following reasons :

• Video signal exhibits a large bandwidth and significant low-frequency content which suggests the use of VSB.  
• VSB (vestigial sideband) transmission transmits one sideband fully and the other sideband partially thus, reducing the bandwidth requirement.
• The circuitry for demodulation in the receiver should be simple and therefore cheap. VSB demodulation uses simple envelope detection.

The spectrum of a vestigial sideband is as shown:

In pulse modulation, message signal in the form of pulses are varied with respect to width, amplitude or position. It is mostly used for radio navigation, microwave band and for many others.

Pulse code modulation (PCM) is a digital form of communication. For demodulation of PCM, it is necessary to convert it into PAM. Quantization noise occurs in PCM only. Signal to quantization noise ratio depends on the number of quantization levels.