Here we use IC8038 as a signal generator to generate modulating and carrier signal. IC1496 a Balance Modulator IC used for modulation purpose, for demodulation purpose simple Diode Detector(Envelop type) is used.

1. Design of AM Modulator &
Demodulator Circuit
Presented by
Sovan Paul

2. Content
• Introduction
• What is Modulation
• Types of Modulation
• Amplitude Modulation
• Modulation Index
• Amplitude Demodulation
• Circuit Diagram
• About Project
• Conclusion

3. Introduction
Communication:
•process of conveying message or information.
•Transmitter modifies message signal into a form which is
suitable for transmission over channel which is achieved by
Modulation

4. What is Modulation
It is a process of transmission of information signal(low
frequency) using a high frequency carrier signal.
Need for Modulation-
•Practicality of Antenna length
•To remove interference
•Reduction of noise

5. Types of Modulation
1.Continuous Wave Modulation –
i. Amplitude Modulation (AM)
ii. Angle Modulation -
(a) Frequency Modulation (FM)
(b) Phase Modulation (PM)
2. Pulse Modulation –
i. Analog type -
(a) Pulse Amplitude Modulation (PAM)
(b) Pulse Duration Modulation (PDM)
(c) Pulse Position Modulation (PPM)
ii. Digital type -
Pulse Code Modulation (PCM)

6. Amplitude Modulation
• The amplitude of high-carrier signal is varied according to the
instantaneous amplitude of the modulating message signal
m(t).
• The modulating signal is the envelope of the carrier
• The required bandwidth is 2B, where B is the bandwidth of the
modulating signal
Why AM?
 circuit is cheaper & Simple
 can be transmitted over long distances.

7. modulating signal :
m(t)cos ωct
carrier signal :
Acos ωct
modulated signal :
A cos ωct + m(t) cos ωct
[A + m(t)] cos ωct
Bandwidth-

8. Modulation Index
The modulation index is defined as the ratio of the modulation
signal amplitude to the carrier amplitude.
If consider carrier signal
ec = Eccos (ωct) and
message signal
em = Em cos (ωmt)
mAM = Em/Ec

9. Amplitude Demodulation
• process of extracting the original information from a
modulated wave

10. Circuit Diagram(1/3)

11. Circuit Diagram(2/3)

12. Circuit Diagram(3/3)

13. About Project

14. Conclusion
We have designed a Frequency Generator (by IC 8038) which can
produce Square, Triangular and Sinusoidal waveforms up to 3-25 kHz
(practically) frequency. When the Sinusoidal message signal and
Carrier signal is fed to the Amplitude Modulator circuit(Balance
Modulator using IC MC1496) we get a amplitude modulated output.
The modulated wave when passed through the Amplitude Demodulator
circuit(Diode Demod.) we get back the message signal in a distorted
form

15. Thank You