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Total No. of Questions : 8] [1] [Total No. of Printed Pages : 2
Roll No ..................................
CS/IT/EE-405 (GS)
B.E. IV Semester Examination, June 2020
Grading System (GS)
Analog and Digital Communication
Time : Three Hours
Maximum Marks : 70
Note: i) Attempt any five questions.
ii) All questions carry equal marks.
1. Define modulation index for FM and PM and obtain the relation between modulation index and
modulating signal for FM and PM.
2. Determine the Power Spectral Density (PSD) of a random process whose autocorrelation function
is given as Ra (t) = A2/2.
3. An Amplitude Modulated wave:
10 ⎡⎣1 + 0.6cos 2π103 t ⎤⎦ cos 2π106 t is to be detected by a linear diode detector Find:
i) The time constant τ
ii) The value of resistance R if the capacitor used is 100pF
4. Write short notes on:
i) Companding
ii) Quantization
5. Find the Channel Capacity of the cascaded channel shown in Fig.
0.8 y1 0.7
x1 → → z1
→ 0.2 → 0.3
0.2 0.3
→ →
x2 → → z2
0.8 y2 0.7
6. How the phase changes in QPSK? Explain in detailed, also discuss advantages and disadvantages of
QPSK.
OR
Draw and explain the circuit diagram of a envelope detector and derive the condition for choice of
time constant.
CS/IT/EE-405 (GS) PTO
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[2]
7. With a block diagram, explain the adaptive Delta Modulation technique.
OR
Prove the following :
i) rxy (1) = ryx ( −1)
ii) rxy (1) = x(1)* y (−1)
8. Answer any three of the following :
a) Explain causal and non-causal systems.
b) State convolution theorem.
c) Draw the amplitude modulation wave forms with modulation Index m = 1, m<1,m>1.
d) Construct NRZ and RZ format for 011010.
e) Sketch the waveform of PSK for binary sequence 1100101.
f) Distinguish between a cyclic code and convolutional code.
******
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Total No. of Questions : 8] [1] [Total No. of Printed Pages : 4
Roll No ..................................
IT-404-CBGS
B.Tech., IV Semester
Examination, December 2020
Choice Based Grading System (CBGS)
Analog and Digital Communication
Time : Three Hours
Maximum Marks : 70
Note: i) Attempt any five questions.
{H$Ýht nm±M àíZm| H$mo hb H$s{OE&
ii) All questions carry equal marks.
g^r àíZm| Ho$ g_mZ A§H$ h¢&
iii) Draw flow charts and Diagram were needed.
Ohm± Amdí¶H$ hmo dhm± âbmo MmQ>© Am¡a S>m¶J«m‘ ~ZmB¶o&
iv) In case of any doubt or dispute the English version
question should be treated as final.
{H$gr ^r àH$ma Ho$ g§Xoh AWdm {ddmX H$s pñW{V ‘| A§J«oOr ^mfm
Ho$ àíZ H$mo A§{V‘ ‘mZm Om¶oJm&
1. a) Draw a block diagram of 8-QAM transmitter and explain
its working. 7
8-QAM Q´>m§g‘rQ>a H$m ãbm°H$ AmaoI ~ZmE± Am¡a BgHo$ H$m¶© H$s
ì¶m»¶m H$a|&
b) What is the purpose of the Fourier transform? How fast
does Fourier transform work? Explain. 7
’y$[a¶a ê$nmÝVaU H$m ³¶m CÔoí¶ h¢? ’y$[a¶a ê$nmÝVaU {H$VZr
VoOr go H$m‘ H$aVm h¢? ì¶m»¶m H$a|&
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[2]
2. a) An AM signal appear across a 50 Ω load and has the
following equation. 7
EH$ AM {g½Zb 50 Ω bmoS> {XImB© XoVm h¢ Am¡a Bg‘| {ZåZ{b{IV
g‘rH$aU h¢&
( )
V ( t ) = 10 1 + sin 2π × 10 × 103 t sin 4π × 106 t
i) Calculate the modulation index, sideband frequencies
total power and bandwidth.
‘m°S>çyboeZ B§S>o³g, gmBS>~¢S> Amd¥{Îm¶m| H$s Hw$b e{º$ Am¡a
~¢S>{dS²>W H$s JUZm H$a|&
ii) Sketch the envelope of SSB signal in time domain.
Also draw the spectrum of SSB signal.
g‘¶ S>m‘o Zo ‘| SSB {g½Zb Ho$ {b’$m’o$ H$m ñHo$M ~Zm¶o& SSB
{g½Zb H$m ñno³Q´>‘ ^r ~ZmE±&
b) What is transmission efficiency? What determines the
band-width of a transmitted AM signal? What will happen
if modulation index is greater than 100%? 7
g§MaU j‘Vm ³¶m h¢? EH$ ào{fV AM {g½Zb H$s ~¢S>{dS²>W ³¶m
{ZYm©[aV H$aVr h¢? ¶{X ‘m°S>çb o Z B§S>³o g 100% go A{YH$ hmo Vmo
y e
³¶m hmoJm&
3. a) What is Modulation? Why we need modulation? 7
‘m°S>çyboeZ ³¶m h¡& ‘m°S>çyboeZ H$s Amdí¶H$Vm ³¶m h¢&
b) What is Modulation index? Draw waveform of a
modulated signal when modulation index is 7
i) ma = 1
ii) ma < 1
iii) ma > 1
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[3]
‘m°S>çyboeZ B§S>o³g ³¶m h¡& ‘m°S>çyboQ>oS> Va§Jmo§ H$mo Xem©B¶o O~{H$
‘m°S>çyboeZ B§S>o³g hmo&
i) ma = 1
ii) ma < 1
iii) ma > 1
4. a) Draw and explain PPM, PAM and PWM schemes. 7
PPM, PAM Ed§ PWM ¶moOZmAm| H$mo g‘PmB¶o Ed§ Xem©B¶o&
b) Explain in detail about the function of each layer in a
Bluetooth system. 7
ãbyQy>W {gñQ>‘ ‘| à˶oH$ naV Ho$ H$m¶© Ho$ ~mao ‘| {dñVma go ~VmE±&
5. a) Compare the various digital modulation techniques. 7
{d{^Þ {S>{OQ>b ‘m°S>çyboeZ VH$ZrH$ H$s VwbZm H$a|&
b) Draw the ASK, FSK, BPSK and QPSK waveforms for the
bit stream 10110001. 7
{~Q> ñQ´>r‘ 10110001 Ho$ {bE ASK, FSK, BPSK Am¡a QPSK
dod’$m°‘© ~ZmBE§&
6. a) Derive the expression for the instantaneous voltage of
AM wave. 7
AM Va§J Ho$ VmËH$m{bH$ dmoëQ>oO Ho$ {bE A{^ì¶{º$ àmá H$a|&
b) Draw the block diagram of CDMA encoder and decoder
and briefly explain. 7
CDMA EZH$moS>a Am¡a {S>H$moS>a Ho$ ãbm°H$ AmaoI H$mo ~ZmBE§& g§jno
‘| dU©Z H$a|&
7. a) Draw the circuit diagram for ring modulator for generating
DSB-SC AM signal. 7
DSB-SC AM {g½Zb OZaoQ> H$aZo Ho$ {bE [a¨J ‘m°S>çb
y Qo >a Ho$ {bE
circuit AmaoI ~ZmE§&
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[4]
b) What is analog modulation? Compare analog modulation
and digital modulation. 7
EZmbm°J ‘mS>çyboeZ ³¶m h¢? {S>{OQ>b ‘mS>çyboeZ Am¡a EZmbm°J
‘mS>çyboeZ ‘| VwbZm H$a|&
8. Write short note on : 14
a) Fourier transform and its properties.
b) TRF and superheterodyne receivers.
c) QAM
d) Compare delta modulation and Adaptive delta modulation
g§{jßV ZmoQ> {bI|&
A) ’y$[a¶a ê$nm§VaU Am¡a BgHo$ JwU
~) TRF Am¡a gwnahrQ>amoS>mBZ [agrda
g) QAM
X) S>oëQ>m ‘mS>çyboeZ Am¡a AZwHy$br S>oëQ>m ‘mS>çyboeZ H$s VwbZm&
******
IT-404-CBGS PTO
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Total No. of Questions : 8] [1] [Total No. of Printed Pages : 3
Roll No ..................................
IT-404-CBGS
B.Tech., IV Semester
Examination, June 2020
Choice Based Grading System (CBGS)
Analog and Digital Communication
Time : Three Hours
Maximum Marks : 70
Note: i) Attempt any five questions.
{H$Ýht nm±M àíZm| H$mo hb H$s{OE&
ii) All questions carry equal marks.
g^r àíZm| Ho$ g_mZ A§H$ h¢&
iii) Draw flow charts and Diagram were needed.
Ohm± Amdí¶H$ hmo dhm± âbmo MmQ>© Am¡a S>m¶J«m‘ ~ZmB¶o&
iv) In case of any doubt or dispute the English version
question should be treated as final.
{H$gr ^r àH$ma Ho$ g§Xho AWdm {ddmX H$s pñW{V ‘| A§JO
o« r ^mfm
Ho$ àíZ H$mo A§{V‘ ‘mZm Om¶oJm&
1. a) Explain the working of a two station data communication
circuit with a block diagram. 7
ãbm°H$ AmaoI Ûmam Xmo ñQ>e
o Z S>Qo >m g§Mma g{H©$Q> Ho$ H$m¶© H$s ì¶m»¶m
H$a|&
b) Draw the spectrum of an AM signal. 7
AM {g½Zb H$m ñno³Q´>‘ ~ZmBE&
2. a) Explain the phasing method of generation of SSB- SC
signal. 7
SSB- SC {g½Zb H$s nr‹T>r> H$s MaU~Õ {d{Y H$s ì¶m»¶m H$a|&
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[2]
b) The available output noise power from an amplifier is 80nw,
the available power gain of the amplifier being 40 dB and
the equivalent noise bandwidth being 25 MHz. Find the noise
figure, assuming room temperature to be 27°C. 7
{H$gr Eåßbr’$m¶a H$s Üd{Z e{³V H$m CËnmXZ 80nw h¡, Eåßbr’$m¶a
Ûmam 40dB H$s e{³V VWm 25 MHz H$s ~¡ÝS>{dS²>W àmßV H$s Om
ahr h¡& ¶{X H$‘ao H$m Vmn‘mZ 27°C h¡ Vmo Üd{Z {MÌ (ÝdmBg
{’$Ja) kmV H$a|&
3. a) Draw the block diagram of Armstrong indirect FM
transmitter and describe its operation. 7
Am‘©ñQ´>mJ§ Aà˶j FM Q´>mg
§ ‘rQ>a H$m EH$ ãbm°H$ AmaoI ~ZmE± Am¡a
BgHo$ g§MmbZ H$m dU©Z H$a|&
b) Discuss the advantages and disadvantages of angle
modulation. 7
E§Jb ‘m°Sw>boeZ Ho$ bm^ Am¡a ZwH$gmZ na MMm© H$a§o&
4. a) Discuss about the generation of PAM and its modulation.7
PAM H$s nr‹T>r Am¡a BgHo$ ‘m°S²>¶yboeZ Ho$ ~mao ‘§o MMm© H$a|&
b) List the source of internal and external noise. 7
AmÝV[aH$ Am¡a ~mhar emoa Ho$ ñÌmoV H$mo gyMr~Õ H$a|&
5. a) Explain the method of generation of QAM and the
demodulation of the same. 7
QAM H$s nr‹T>r H$s {d{Y Am¡a Cgr Ho$ S>r‘m°S²>¶yboeZ H$s ì¶m»¶m
H$a|&
b) Draw the AKS, FSK, PSK waveform for digital data
10100110. 7
AKS, FSK, PSK Ho$ Va§J H$mo {S>{OQ>b S>mQ>m 10100110 Ho$ {bE
AmH${f©V H$a§o&
IT-404-CBGS Contd...
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[3]
6. a) Define mutual information and mention its properties. 7
å¶wMwAb gyMZm Am¡a BgHo$ JwUm| H$s ì¶m»¶m H$a|&
b) What is the various pulse modulation techniques? Give
one method for the generation of PAM. 7
{d{^Þ nëg ‘m°S>² ¶b o Z VH$ZrH$ ³¶m h¡? PAM H$s nr‹T>r Ho$ {bE
y e
EH$ {d{Y àñVwV H$a§o&
7. a) Explain the QAM transmitter and receiver. 7
QAM Q´>m§g‘rQ>a Am¡a [agrda H$s ì¶m»¶m H$a|&
b) Draw the block diagram for explaining the working of
coherent binary FSK transmitter and receiver. 7
gwg§JV ~mBZar FSK Q´>m§g‘rQ>a Am¡a [agrda Ho$ H$m‘H$mO H$s
ì¶m»¶m Ho$ {bE EH$ ãbm°H$ AmaoI ~ZmBE&
8. Write short note on 14
a) Transform of gate
b) Foster Seeley discriminator
c) Shifting property of delta function
d) Natural and flat top
g§{jßV ZmoQ> {bI|&
A) JoQ> H$m ê$nmÝVaU
~) ’$moñQ>a {gbr {S>ñH«$s‘rZoQ>a
g) S>oëQ>m ’§$³eZ H$s ñWmZm§VaU bjU
X) àmH¥${VH$ Am¡a gnmQ> erf©
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