HKBK College of Engineering, Bangalore
Dept. of Electronics & Communication Engineering
Academic Year 2024-25
IV Semester ECE
BEC402: Principles of Communication Systems
Module 3: Fundamentals of Frequency Modulation Dr. Suraiya Tarannum
Q CO RBT Question
# #
1. 1 2 Explain Frequency Modulation (FM) with necessary equations and
sketches in time-domain and frequency-domain.
2. 1 2 (i) With a neat block diagram, explain how to convert a Phase Modulated
(PM) signal into a Frequency Modulated (FM) signal.
(ii) With a neat block diagram, explain how to convert a Frequency
Modulated (FM) signal into a Phase Modulated (PM) signal.
3. 1 3 With necessary analysis derive an expression for FM of the form,
𝑆(𝑡) = 𝐴𝑐 cos(2𝜋𝑓𝑐 𝑡 + 𝛽 𝑠𝑖𝑛2𝜋𝑓𝑚 𝑡)
Draw the time-domain and frequency domain representation of the FM
wave.
4. 1 3 Write a MATLAB code to generate Frequency Modulation (FM) and
Demodulation waveforms and display the frequency spectrum using the
frequency domain representation.
5. 1 3 Determine the Frequency Modulated (FM) signal,
𝑣𝐹𝑀 = 𝑣𝑐 sin(2𝜋𝑓𝑐 𝑡 + 𝑚𝑓 𝑠𝑖𝑛2𝜋𝑓𝑚 𝑡)
in terms of Bessel’s functions. Write the amplitude of sideband frequencies
(𝐽𝑛 ) in terms of Modulation Index (𝑚𝑓 ).
6. 1 3 An FM wave is defined by,
𝑆(𝑡) = 10 cos(10𝜋𝑡 + 𝑠𝑖𝑛 4𝜋𝑡)
Calculate the instantaneous frequency of 𝑆(𝑡).
7. 1 2 A transmitter operates on a frequency of 915 MHz. The maximum FM
deviation is ±12.5 kHz. What are the minimum and maximum frequencies
that occur during modulation?
8. 1 2 What is the Deviation Ratio if the maximum deviation is 25 kHz and the
maximum modulating frequency is 15 kHz? Determine the transmission
bandwidth using Carson’s Rule.
9. 1 2 What is the maximum modulating frequency that can be used to achieve a
modulation index of 2.2 with a deviation of 7.48 kHz. Determine the
transmission bandwidth using Carson’s Rule.
10. 1 2 What is the maximum bandwidth of an FM signal with a deviation of 30
kHz and a modulating signal of 5 kHz using,
(i) Carson’s Rule (ii) Number of sidebands N=9.
11. 1 3 Explain the Noise Suppression Effects of a Frequency Modulated (FM)
signal.
12. 1 3 The input to an FM receiver having a Signal-to-Noise Ratio, S/N of 2.8.
The modulating frequency is 1.5 kHz. The maximum permitted deviation if
4 kHz. Determine,
(a) the Frequency Deviation caused by the noise and
(b) the improved Output S/N ratio?
13. 1 3 Compare and contrast FM and AM.
14. 2 2 With a neat block diagram, explain the generation of Frequency
Modulation (FM) signal using the Voltage Controlled Oscillator (VCO) IC
Page 1 of 3
HKBK College of Engineering, Bangalore
Dept. of Electronics & Communication Engineering
Academic Year 2024-25
IV Semester ECE
(IC NE566).
15. 2 2 Explain with neat diagrams, the working principle of an FM wave using a
Crystal Oscillator.
16. 2 2 Compare and contrast FM using Crystal Oscillator and generation of FM
using Varactor.
17. 2 2 Explain the working principle of Phase Locked Loop (PLL) with a neat
block diagram. Explain ’Capture Range’ and ‘Lock Range’ of the PLL.
18. 2 2 Explain the working principle of Phase Locked Loop (PLL). Explain with
neat diagrams, the FM Demodulation technique using the PLL IC (IC 565).
19. 2 2 With a neat block diagram of a Super Heterodyne Receiver, explain the
function of each of blocks therein.
20. 2 2 Interpret the concept of a Mixer with a neat block diagram.
Page 2 of 3
HKBK College of Engineering, Bangalore
Dept. of Electronics & Communication Engineering
Academic Year 2024-25
IV Semester ECE
BEC402: Principles of Communication Systems
Dr. Suraiya Tarannum
Module 3: Fundamentals of Frequency Modulation
Assignment 3
Date of Issue: 17/4/2025 Date of Submission: 5/5/2025
Q# CO# RBT Question
1. 1 2 Explain Frequency Modulation (FM) with necessary equations and diagrams
in time-domain and frequency-domain (Frequency Spectrum).
2. 1 2 With a neat block diagram, explain how to convert a Phase Modulated (PM)
signal into a Frequency Modulated (FM) signal and vice-versa.
3. 1 3 Write a MATLAB code to generate Frequency Modulation (FM) and
Demodulation waveforms and display the frequency spectrum in the
frequency domain representation.
4. 1 3 With necessary analysis derive an expression for FM given by,
𝑆(𝑡) = 𝐴𝑐 cos(2𝜋𝑓𝑐 𝑡 + 𝛽 𝑠𝑖𝑛2𝜋𝑓𝑚 𝑡)
Draw the time-domain and frequency domain representation of the FM
wave.
5. 1 3 Determine the Frequency Modulated (FM) signal,
𝑣𝐹𝑀 = 𝑣𝑐 sin(2𝜋𝑓𝑐 𝑡 + 𝑚𝑓 𝑠𝑖𝑛2𝜋𝑓𝑚 𝑡)
in terms of Bessel’s functions. Write the amplitude of sideband frequencies
(𝐽𝑛 ) in terms of Modulation Index (𝑚𝑓 ).
6. 1 3 An FM wave is defined by,
𝑆(𝑡) = 10 cos(10𝜋𝑡 + 𝑠𝑖𝑛 4𝜋𝑡)
Calculate the instantaneous frequency of 𝑆(𝑡).
7. 1 2 A transmitter operates on a frequency of 915 MHz. The maximum FM
deviation is ±12.5 kHz. What are the minimum and maximum frequencies
that occur during modulation?
8. 1 2 What is the Deviation Ratio if the maximum deviation is 25 kHz and the
maximum modulating frequency is 15 kHz? Determine the transmission
bandwidth using Carson’s Rule.
9. 1 2 What is the maximum modulating frequency that can be used to achieve a
modulation index of 2.2 with a deviation of 7.48 kHz. Determine the
transmission bandwidth using Carson’s Rule.
10 1 2 What is the maximum bandwidth of an FM signal with a deviation of 30 kHz
and a modulating signal of 5 kHz using,
(i) Carson’s Rule (ii) Number of sidebands N=9.
11. 1 3 Explain the Noise Suppression Effects of a Frequency Modulated (FM)
signal.
12. 1 3 The input to an FM receiver having an S/N of 2.8. The modulating frequency
is 1.5 kHz. The maximum permitted deviation if 4 kHz. Determine,
(a) the Frequency Deviation caused by the noise and
(b) the improved Output S/N ratio?
13. 1 3 Compare and contrast FM and AM.
14. 2 2 With a neat block diagram of a Super Heterodyne Receiver, explain the
function of each of blocks therein.
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