PROJECT REPORT
FREQUENCY
MODULATION AND
DEMODULATION USING
DIFFERENTIATOR
TEAM MEMBERS
FATIMA IQBAL
DANIYA IMRAN
NOOR TAHIR
SUBMITTED TO
DR. HUMA GHAFOOR
FM Modulation and Demodulation using
Differentiator
ABSTRACT:
Objectives:
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Our project revolves around frequency modulation and demodulation using a differentiator circuit.
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We focused on creating a cost-effective practical system with accurate and easy hardware
implementations for frequency modulation and demodulation.
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We also simulated our circuit on Proteus thus comparing both the hardware and software results.
Modulation:
“Modulation is a process that is used to impress the information of the message signal onto the carrier
wave, which is used to carry the information to another location”.
Types of Modulation:
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ANGULAR MODULATION:
“Angle Modulation is the process in which the frequency or the phase of the carrier varies according to
the message signal”.
TYPES OF ANGULAR MODULATION:
This is further divided into
➢ Frequency modulation
➢ Phase modulation
FREQUENCY MODULATION:
“The process of varying the frequency of the carrier signal linearly with the message signal (the signal to be
transmitted).”
APPLICATIONS OF FREQUENCY MODULATION:
Frequency modulation comes with a number of real-life applications such as
➢ FM radio broadcasting
➢ Radar
➢ Seismic prospecting
➢ Telemetry
➢ Music synthesis
➢ Two-way radio systems
➢ Magnetic tape-recording systems
➢ Video broadcast systems
ADVANTAGES OF FREQUENCY MODULATION:
The major advantages of using frequency modulation over amplitude modulation include
➢ Improved signal to noise ratio
➢ Smaller geographical interference between neighboring stations.
➢ Less power consumption
MATHEMATICAL EXPRESSION:
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METHODS FOR FREQUENCY MODULATION:
FM signals can be generated using either direct or indirect frequency modulation:
➢ Direct frequency modulation in which the message is inputted directly into a voltage-controlled
oscillator.
➢ Indirect frequency modulation, which is achieved by integrating a message signal to generate a phasemodulated signal. The phase modulated signal is then further used to modulate a crystal-controlled
oscillator, the result of which is transmitted through a frequency multiplier to produce an FM signal.
FREQUENCY DEMODULATION:
FM demodulation is a key process in the reception of a frequency modulated signal.
“The process of recovering the original signal from the modulated carrier once the signal has been received,
filtered and amplified It is this process that is called demodulation or detection”.
METHODS FOR FREQUENCY DEMODULATION:
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DIFFERENTIATOR CIRCUIT:
Differentiation is performed by an operational amplifier circuit. It produces a voltage output which is directly
proportional to the input voltage’s rate-of-change with respect to time.
The differentiator circuit is essentially a high-pass filter.
For a passive RC differentiator circuit, the input is connected to a capacitor while the output voltage is taken
from across a resistance being the exact opposite to the RC Integrator Circuit.
ENVELOPE DETECTOR:
An envelope detector also called as peak detector is an electronic circuit that takes a (relatively) highfrequency amplitude modulated signal as input and provides an output, which is the demodulated envelope of
the original signal.
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CIRCUIT FOR FM MODULATION:
➢ Carrier Frequency: 500kHz
➢ Message Frequency: 50kHz
COMPONENTS USED:
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Breadboard
Variable Capacitance
Capacitor
Resistor
Inductor
Transistor (BJT)
Jumper wires
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CIRCUIT FOR FM DEMODULATION:
COMPONENTS USED:
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Diode
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OP amp 741
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Resistor
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Capacitor
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Jumper wires
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Breadboard
HARDWARE IMPLEMENTATION
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Modulation Circuit
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Demodulation Circuit
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RESULTS OBTAINED:
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Modulation
▪ Demodulation
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PROTEUS SIMULATION:
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Modulation
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Demodulation
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Simulation Results:
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CONCLUSION:
The project allowed us to have a deeper understanding of FM modulation and demodulation.
➢ We physically implemented the wave modulation concepts in order to perform frequency
modulation of the given message signal to be transmitted.
➢ The modulated signal was further demodulated it through a differentiator circuit
connected with an envelope detector.
➢ Implementing the circuit on hardware and then comparing the results to those obtained by
proteus simulation allowed us to comprehend the accuracy of our results and the
corresponding errors.
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