SD-R22
Code No:
SRIDEVI WOMEN’S ENGINEERING COLLEGE
(UGC - AUTONOMOUS)
B. Tech. II Year II Semester Regular Examinations, June 2025
ANALOG AND DIGITAL COMMUNICATIONS
(ECE)
Time: 3 Hours Max. Marks: 60
Note: (i) This Question Paper consists of Part A and Part B.
(ii) Part A is compulsory, which carries 10 marks. Answer all questions of Part A at one place only.
(iii) In Part-B, Answer any ONE question from each unit. Each question carries 10 marks
PART – A (10x1 = 10 Marks)
Bloom’
Q.no Mark
Question s
. s
Level
1 a) Define DSB-SC. 1M L1
1 b) What is the need for modulation? 1M L1
1 c) What do you understand by narrowband FM? 1M L1
When the modulation index is less than 1, the angle modulated systems
are called low index. The
bandwidth requirement of low index systems is approximately twice of
the modulating.
What do you understand by narrowband FM?
When the modulation index is less than 1, the angle modulated systems
are called low index. The
bandwidth requirement of low index systems is approximately twice of
the modulating.
What do you understand by narrowband FM?
When the modulation index is less than 1, the angle modulated systems
are called low index. The
bandwidth requirement of low index systems is approximately twice of
the modulating.
What do you understand by narrowband FM?
When the modulation index is less than 1, the angle modulated systems
are called low index. The
bandwidth requirement of low index systems is approximately twice of
the modulating.
What do you understand by narrowband FM?
When the modulation index is less than 1, the angle modulated systems
are called low index. The
bandwidth requirement of low index systems is approximately twice of
the modulating.
What are the two methods for producing FM signal?
1 d) Define frequency modulation. 1M L1
1 e) Compare low level and high level Transmitters. 1M L6
1 f) What are the different types of AGC? 1M L1
1 g) Distinguish between PAM and PWM 1M L4
1 h) Compare FDM & TDM. 1M L6
1 i) Why is PSK always preferable over ASK in coherent detection? 1M L1
1 j) Define Coherent detection. 1M L1
PART – B (5x10 = 50 Marks)
Bloom’
S.n Mark
Question s
o s
Level
UNIT-I
2. a) Explain the generation of DSB-SC using balanced modulator. 5M L2
b) Explain the demodulation of AM using Envelope 5M L2
detector
OR
3 a) Derive necessary equations for Power relations in AM waves. 5M L5
b) An AM transmitter radiates 50W power when carrier is 5M L6
modulated and μ=0.707. Determine
i) Carrier power ii) modulation efficiency.
UNIT-II
4. a) Discus the generation of FM using Armstrong method 5M L2
with a neat block diagram.
b) Explain the detection of FM using Balanced Slope detector.. 5M L2
OR
5. a) Derive the expression for Narrowband FM signal. Draw 5M L5
its Phase representation
b) Discuss the process of Detection of FM Waves by Phase locked loop. 5M L2
UNIT-III
6. a) Draw the block diagram of AM transmitter using low level 7M L4
modulation. Explain the significance of each block.
b) Discuss about frequency stability in FM Transmitter. 3M L2
OR
7. a) Explain the operation of Super Heterodyne Receiver using a neat 7M L2
block diagram
b) List out the advantages and disadvantages of TRF receiver. 3M L1
UNIT-IV
8 a) Discuss the working of Delta 5M L2
modulation with neat block diagram.
b) Explain the need for non-uniform quantization in digital 5M L2
communications.
OR
9. a) With a neat block diagram explain the generation of PWM signals. 5M L4
b) Describe the generation and demodulation of PPM with the help of 5M L6
block diagram
UNIT-V
10. a) Write a note on QPSK Modulator and demodulator. Draw its phasor 5M L3
and constellation diagram.
b) Write short notes on (a) ISI (b) Eye Diagrams. 5M L3
OR
11. a) Explain the concept of QAM. 5M L2
b) Explain detection of FSK using PLL. 5M L2
SD-R22
Code No:
SRIDEVI WOMEN’S ENGINEERING COLLEGE
(UGC - AUTONOMOUS)
B. Tech. II Year II Semester Regular Examinations, June 2025
ANALOG AND DIGITAL COMMUNICATIONS
(ECE)
Time: 3 Hours Max. Marks: 60
Note: (i) This Question Paper consists of Part A and Part B.
(ii) Part A is compulsory, which carries 10 marks. Answer all questions of Part A at one place only.
(iii) In Part-B, Answer any ONE question from each unit. Each question carries 10 marks
PART – A (10x1 = 10 Marks)
Bloom’
Q.no Mark
Question s
. s
Level
1 a) Define modulation index for AM 1M L1
1 b) A 400W carrier is modulated to a depth of 75 %. Calculate the total 1M L6
power in the modulated wave? Solution: Pc = 400 Wm = 0.75 Pt=?
1 c) Define Phase Modulation. 1M L1
1 d) Compare WBFM and NBFM. 1M L6
1 e) What is the purpose of an AGC circuit in a TV receiver? 1M L1
1 f) What is the use of Amplitude limiter? 1M L1
1 g) List the errors in Delta Modulation. 1M L1
1 h) Define Quantization Error. 1M L1
1 i) What is an eye pattern? 1M L1
1 j) Distinguish between ASK & FSK. 1M L4
PART – B (5x10 = 50 Marks)
Bloom’
S.n Mark
Question s
o s
Level
UNIT-I
2. a) Explain generation of AM using Switching Modulator 5M L2
b) Derive the time domain expression for SSB signal with 5M L5
only USB being transmitted
OR
3 a) Explain about Costas loop. 5M L2
b) Explain the coherent detection of DSB-SC. 5M L2
UNIT-II
4. a) Discuss the need of pre-emphasis and de-emphasis in FM. 5M L2
b) Describe the generation of NBFM. 5M L6
OR
5. a)Derive the expression for single tone frequency modulated 5M L5
signal
b) Explain the generation of WBFM. 5M L2
UNIT-III
6. a) Explain the operation of High level AM Transmitter with a neat block 5M L2
diagram
b) Explain the different types of AGC. 5M L2
OR
7. a) Explain the operation of Tuned Radio frequency Receiver using a neat 5M L2
block diagram.
b) Explain the operation of Super Heterodyne Receiver using a neat 5M L2
block diagram
UNIT-IV
8 a) Explain the operation of Adaptive 5M L2
Delta Modulation transmitter and
receiver.
b) Explain the generation and demodulation of PAM. 5M L2
OR
9. a) Draw the block diagram of PCM and explain function of each block. 5M L5
b) Compare PAM, PWM and PPM pulse modulation techniques. 5M L6
UNIT-V
10. a) Derive the equation for probability of error using BPSK in Base 5M L5
band transmission.
b) Explain Eye Diagrams with neat diagrams. 5M L2
OR
11. a) Explain detection of FSK using PLL. 5M L2
b) Explain the process of generating ASK signals 5M L2
