15-12-2012, 01:57 PM
Communication Systems Lab
[attachment=43917]
AIM:
To construct a Amplitude modulator circuit & demodulate the Amplitude
modulated wave.
THEORY :
The modulation is simply a method of combining two different signals and is used in
the transmitter section of a communication system. The two signals that are used are the
information signal and the carrier signal. Amplitude Modulation is the simplest form of
signal processing in which the carrier amplitude is simply changed according to the
amplitude of the information signal hence the name Amplitude modulation. When the
information signals amplitude is increased the carrier signals amplitude is increased and
when the information signals amplitude is decreased the carrier signals amplitude .
PROCEDURE:
1. Circuit connections are given as shown in the circuit diagram.
2. The power supply is connected to the collector of the transistor.
3. Using AFO the carrier signal is given to the base of the transistor.
4. The modulating (message or base band) signal is given to the emitter of the
transistor.
5. From the collector of the transistor, the modulated wave is noted down using
CRO.
6. By varying the amplitude of the modulating signal the values of Emax and Emin are
noted down to find the modulation index.
7. The amplitude modulated wave is now given as the input to the detector circuit.
8. The demodulated (message) wave amplitude and frequency is noted down from
the CRO.
[attachment=43917]
AIM:
To construct a Amplitude modulator circuit & demodulate the Amplitude
modulated wave.
THEORY :
The modulation is simply a method of combining two different signals and is used in
the transmitter section of a communication system. The two signals that are used are the
information signal and the carrier signal. Amplitude Modulation is the simplest form of
signal processing in which the carrier amplitude is simply changed according to the
amplitude of the information signal hence the name Amplitude modulation. When the
information signals amplitude is increased the carrier signals amplitude is increased and
when the information signals amplitude is decreased the carrier signals amplitude .
PROCEDURE:
1. Circuit connections are given as shown in the circuit diagram.
2. The power supply is connected to the collector of the transistor.
3. Using AFO the carrier signal is given to the base of the transistor.
4. The modulating (message or base band) signal is given to the emitter of the
transistor.
5. From the collector of the transistor, the modulated wave is noted down using
CRO.
6. By varying the amplitude of the modulating signal the values of Emax and Emin are
noted down to find the modulation index.
7. The amplitude modulated wave is now given as the input to the detector circuit.
8. The demodulated (message) wave amplitude and frequency is noted down from
the CRO.