Single Sideband Suppressed Carrier(SSB-SC) Modulation MCQ Quiz in తెలుగు - Objective Question with Answer for Single Sideband Suppressed Carrier(SSB-SC) Modulation - ముఫ్త్ [PDF] డౌన్‌లోడ్ కరెన్

Concept:

SSB (Single Side Band) modulation is a technique that allows only one sideband to pass saving bandwidth and power both. Practically it is very difficult to pass only a single sideband.

Analysis:

Ex: If we consider a single-tone modulating signal as x(t) = cos ωmt, the SSB modulated wave with only the upper sideband will be represented as:

cos ((ωc + ωm)t) = cos ωc.cos ωmt – sin ωc.sin ωmt

and with lower sideband only will be represented as:

cos (ωc - ωm)t = cos ωct .cos ωmt + sin ωct. sin ωmt

where sin ωmt is the Hilbert transform of the original message signal x(t) = cos ωmt

Conclusion:

Generalizing this for any signal m(t), we can say that the SSB modulated signal with only upper sideband will be:

m(t) cos ωct – m̂(t) sin ωct,

Similarly, we can say that the SSB modulated signal with only lower sideband will be:

m(t) cos ωct + m̂(t) sin ωct,

where m̂(t) is the Hilbert transform of m(t).

SSB/SC is generated using a balanced modulator circuit as shown:

Where π/2 phase shifter gives the Hilbert transform of the incoming signal. 

Concept: 

The total transmitted power for an AM system is given by:

\({P_t} = {P_c}\left( {1 + \frac{{{m^2}}}{2}} \right)\)

Pc = Carrier Power

m = Modulation Index

Analysis:

The above expression can be expanded to get:

\({P_t} = {P_c} + P_c\frac{{{m^2}}}{2}\)

The total power is the sum of the carrier power and the sideband power, i.e.

\({P_s} = P_c\frac{{{m^2}}}{2}\)

In conventional AM transmission, the power is equally distributed between the two sidebands, i.e.

\(P_{upper} = P_{lower}=P_c\frac{m ^2}{4}\)

∴ The power contained in a single sideband in amplitude modulation is \(\frac{{{m^2}{P_c}}}{4}\)

Let, the channel is practical having finite attenuation of 'A' dB, and the single-sided noise power spectral density is given as 'N' W/Hz

∴ \(10\log \frac{{{P_t}}}{{{P_r}}} = A\)

\(Received~power~({\rm{P_r}}) = {10^{ - \frac{{\rm{A}}}{{10}}}}\;{P_t}\) 

\(SNR = \frac{{{P_r}}}{{{P_n}}}\) 

P_n = 2N × (B.W)

Let the message signal spectrum is given as:

In the case of AM:-

B.W = 2f_m kHz (twice of message signal bandwidth)

\(SN{R_1} = \frac{{{{10}^{ - \frac{A}{{10}}}}\;{P_t}}}{{4\;Nf_m}}\) 

In the case of SSB:-

B.W = f_m kHz (same as message signal bandwidth)

\(SN{R_2} = \frac{{{{10}^{ - \frac{A}{{10}}}}{P_t}}}{{2Nf_m}}\) 

∴ \(SN{R_1} = \frac{{SN{R_2}}}{2}\)

∴ SNR in the case of S.S.B is double that in the case of AM.

Statement-I is incorrect and Statement-II is correct.

For \(\rm SSB\), the general expression is

\(\rm {X_{SSB}}\left( t \right) = m\left( t \right)\cos {\omega _c}t \pm \hat m\left( t \right)\sin {\omega _c}t\)

for\(\rm \;m\left( t \right) = \cos \left( {2\pi {f_m}t} \right)\),

We get,

\(\rm {X_{SSB}}\left( t \right) = \cos \left( {2\pi {f_m}t} \right)cos{\omega _c}t \pm \sin \left( {2\pi {f_m}t} \right)\sin {\omega _c}t \\ \ \ \ \ \ \ \ \ \ \ \ \ \ = {\rm{cos}}\left[ {2\pi \left( {{f_c} + {f_m}} \right)t} \right]\)

The correct answer is Only i and ii

Key Points

• Turtle Wildlife Sanctuary is located in Varanasi district of Uttar Pradesh and is the first sanctuary dedicated to freshwater turtles in India.
• It was the first freshwater turtle wildlife sanctuary in the country, established with the aim of conserving the turtle species found in the region.
• The turtles were indeed released into the sanctuary to help with the organic removal of half-burnt human corpses, as the sanctuary is located near the Assi Ghat of the Ganges River, where many corpses are left to float after cremation.
• The sanctuary aims to maintain a delicate ecological balance by promoting this natural method of cleaning the river while protecting the species that call the Ganges home.

 Additional Information

• Statement iii
  • The statement regarding the promotion of organic removal of half-burnt human corpses is partially true. While this natural method of cleaning is encouraged in the region, it is not the primary purpose of the sanctuary.
  • The primary goal of the Turtle Wildlife Sanctuary is conservation and protection of the turtle species, although the natural cleansing of the Ganges is an incidental outcome.

• In SSB (Single Side-band), only one side-band is necessary for the transmission of information.
• This reduces the Bandwidth requirement to half.
• A typical SSB transmission spectrum is as shown:

• For SSB transmission, it does not matter whether the upper or lower sideband is used, since the information is contained in both.

Hilbert Transformer transforms the input signal as:

1) The magnitude of the frequency component present in x(t) remains unchanged when it is passed through the system.

2) The phase of the positive frequency components is shifted by -π/2, and that of the negative frequency components is shifted by +π/2.

Concept:

The general expression of an SSB modulated signal is:

S_SSB(t) = m(t) cosω_ct ± m̂(t) sinω_ct

A plus sign implies the Lower-sideband signal and minus sign implies an Upper sideband signal.

m(t) = Message signal

ω_c = Carrier signal frequency

m̂(t) = Hilbert transform of the message signal

Hilbert Transformer transforms the input signal as:

1) The magnitude of the frequency component present in x(t) remains unchanged when it is passed through the system.

2) The phase of the positive frequency components is shifted by -π/2 and that of negative frequency components is shifted by +π/2.

Application:

m(t) = cos 30t and ω_c = 850 rad/sec

The Hilbert transform of the above signal will be:

m̂(t) = cos (30t – 90°) = sin 30 t

For lower side band, the SSB expression will be:

s_L(t) = m(t) cos ω_c t + m̂(t) sin ω_ct

Putting on the respective function values, we get:

sL(t) = cos 30t cos 850t + sin 30t sin 850t

sL(t) = cos (850 - 30)t

Key Points

• Phase Discrimination is used for the demodulation of Frequency Modulate signals.

Additional Information 

• The following methods are used for the demodulation of Single Side Band (SSB) signals.
  • The Filter Method
  • The Phasing Shift Method
  • The Weaver Demodulator
  • Fourier based Demodulation.
• The following methods are used for the demodulation of Frequency Modulated (FM) signals.
  • ​Frequency discrimination method
  • Phase discrimination method.

​

SSB-SC:

• The process of suppressing one of the sidebands, along with the carrier, and transmitting a single sideband is called as Single Sideband Suppressed Carrier system, or SSB-SC or SSB. 
• The system that transmits a single sideband, has high power, as the power allotted for both the carrier and the other sideband is utilized in transmitting this Single Sideband (SSB).

The process of extracting an original message signal from the SSBSC wave is known as detection or demodulation of SSBSC.

Demodulation of the SSB-SC:

1) Using PRODUCT MODULATOR

2) Using DIODE BALANCED MODULATOR

3) Using COMPLETE PHASE SHIFT GENERATOR

DIAGARM From LMS (diagram was blur)

4) Bipolar transistor balanced modulator:

It is used in the demodulation of the DSB-SC signal and not SSB-SC.