Al-Balqa' Applied University
Faculty of Engineering Technology
Laboratory Commonucations
Experiement Amplitude Modulation
Name Ahmad Imad Hasan Issa
Reg Number 31815020024
Instructor Dr. Aws Alqaisy
Lab Time Wed 2-5
Date 9/3/2021
Abstract:
In this experiment we studied about AM modulation so I'm going to
discuss in this report about it
First, we will discuss about the objectives of the experiment then we will
mention the tools that we used in this experiment after that we will
discuss more about the experiment as in this report
Objectives:
- Examine the main parameters of an amplitude modulated signal.
- Check the operation of an amplitude modulator.
- Carry out the characteristic measurement on an amplitude
modulator.
Materials:
- basic unit (power supply mod. PSU/EV, module-holder unit
- mod. MU/EV, individual control unit mod. SIS1/SIS2/SIS3).
- experiment module mod. MCM21/EV.
- dual trace oscilloscope.
function generator. -
frequency meter -
Theory:
Amplitude Modulation Generation:
The circuits used to an amplitude modulation must vary the
amplitude of a high frequency signal (carrier) as function of the
amplitude of a low frequency signal (modulating signal).
In AM transmitter we speak of:
high level modulation, if the modulation is carried out directly in
the last power stage, which is generally an amplifier in class C.
low frequency modulation, when the modulation is carried out by
stages which are before the final power amplifier.
Semiconductor devices can be used in the case of low power, or
valve ones, when the required power is high.
In the circuit used for the exercises, the amplitude modulation
is generated by a differential amplifier, which gain is varied by the
modulating signal. This circuit, contained in the integrated circuit
LM1496, can be used also to generate the amplitude modulation
with suppressed carrier, object of another exercises.
The integrated circuit LM1496 consists of a quadruple
differential amplifier, driven by a further differential stage
Operation of the modulator:
1- Use Balance modulator 1 circuit.
(Fig1)
2- Across the input Carrier (TP7), apply a sine signal with about
1 Vp-p amplitude and about 450 kHz-frequency; this signal can
be taken from the output of the VCO2(TP18).
3- Connect at terminal TP8 and ground the function generator
with sine wave, 0.5 Vp-p amplitude, 1-kHz frequency.
4- Turn the trimmer Carrier Null completely clockwise or
counterclockwise, so to "unbalance" the modulator and to
obtain an AM signal with not suppressed carrier across the
output, Level in intermediate position.
5- Connect the oscilloscope to the inputs of the modulator (TP7
and TP8) and detect the signal and modulating signal.
6- Move the probe from TP7 to TP9 (output of the modulator).
Conclusion:
• The information of the message signal will be saved on the
amplitude.
Advantages of Amplitude Modulation:
• It is simple to implement.
• Demodulation of AM signals can be done using simple circuits
consisting of diodes.
• AM transmitters are less complex.
• AM receivers are very cheap as no specialized components are
needed.
• AM waves can travel a longer distance.
• AM waves have low bandwidth.
Disadvantages of Amplitude Modulation:
• An amplitude modulation signal is not efficient in terms of its
power usage.
• It is not efficient in terms of its use of bandwidth.
• AM detectors are sensitive to noise hence an amplitude
modulation signal is prone to high levels of noise.
• Reproduction is not high fidelity
