ENB6060
TELECOMMUNICATIONS A
LABORATORY SHEET 1
Amplitude Modulation
Name:- (Type Your Name Here)
Student ID :- (Type Your Student ID Here)
Objective
The objective of this assignment is to become more familiar with Amplitude Modulation. The type of modulation scheme covered in this Assignment will be DSB-SC (Double Sideband Suppressed Carrier). The first part of this exercise will involve a simple simulation of an Amplitude Modulation Scheme using MatLab. The second part of this lab will involve the construction of an Amplitude Modulation scheme.
Apparatus
· MatLab installed on PC in Lab (Part A)
· AD633JNZ Multiplier (Part B)
Method
Part A of this lab has been designed to simulate and plot a DSB-SC modulated signal using the theory developed and provided to the students. The second part will involve the implementation of a DSB-SC modulated signal using the AD633JNZ Multiplier.
Marking Scheme
Part A / Marks AssignedMatLab Code + Comments / 10
Graphs obtained / 10
Part B
Graphs + Comments / 10
MatLab Code + Comments / 30
Discussion
Discussion of results / 10
Comparative Analysis / 10
Conclusions
Brief Description of Work / 10
Most Relevant Information / 10
Part A
The first part of this lab will involve using MatLab to simulate a DSB-SC system. It has been seen from class that this is achieved by multiplying the Baseband signal with the Carrier signal. A mathematical description of this process is as follows:
For your MatLab Code use the following parameters:
· Baseband Frequency = The Last Digit of your ID multiplied by 1000 (see example below)
· Carrier Frequency = Baseband signal Frequency multiplied by 100 (see example below)
· Baseband Amplitude = Choose a value between 0.5 V and 1 V
· Carrier Amplitude = Baseband Signal Amplitude
Frequency Example :- For a student ID = 20900227 the frequency is 7 x 1000 = 7000 = 7KHz, in this case the frequency of the carrier signal is going to be 7000 x 100 = 700,000 = 0.7 MHz. If the case arises where the last digit of your ID is 0 then use the second last digit, i.e. for 20900220 use 2.
Tasks
1. Plot your baseband signal, you may remove the example baseband signal presented in this document and paste your own, provide a brief discussion on the signal obtained.
2. Plot the Carrier signal, you may remove the example carrier signal presented in this document and paste your own, provide a brief discussion on the signal obtained
3. Plot the Amplitude Modulated Signal, you may remove the example signal plot in this document and paste your own, provide a brief discussion on the signal obtained.
4. After your different plots, paste in the fully commented MatLab code you have generated in your m-file.
Figure 1 Baseband signal of 500Hz
Figure 2 Carrier Signal of 10 KHz
Figure 3 Amplitude Modulated signal
Part B
In this part of the assignment you will be provided with an Analog Multiplier (AD633JNZ). The data sheet for this device will be provided on the Bahrain Polytechnic moodle site. Read the datasheet carefully before attempting to setup your circuit.
Make a list of the most important parameters, giving the reasons why you selected them:
______
Use the protoboard on the Elvis Platform to build your circuit. Open the NI ELVISmx Instrument Launcher, (see Figure 4).
Figure 4 Instrument launcher
You will require two signal generators to complete this lab, one for the carrier wave and a second for the baseband signal. Use the FGEN (see Figure 5) for the carrier wave and set it to the value obtained From Part A for both the frequency and amplitude. Use the ARB (Arbitrary Waveform Generator, see Figure 6) to generate a sinewave for the Baseband signal, again use the baseband signal frequency and amplitude from Part A.
Copy and paste a copy of the input and output waveforms you obtain from the experiment into this document, see Figure 7 for an example of the output waveform. Use the spectrum analyzer to observe the input and output signals obtained and paste them into this document. Provide a discussion on each of the signals obtained.
Finally, use the Log Button on the Oscilloscope to obtain the data. Write a Matlab script file to plot this data. Paste the graph you obtain into this document (see Figure 8) along with the fully commented Matlab code.
Figure 6 Arbitrary Waveform Generator
Figure 7 Waveform obtained from Experimental Measurement
Figure 8 Matlab representation of the experimental data obtained
Discussion
(Provide a discussion on the work performed here. Provide details on any calculations and results you obtained. Provide a comparison between the theoretical and experimental results.)
Conclusions
(Provide Conclusions for the work performed in this lab. In the conclusions provide details of the most significant values you have obtained.)
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Revised 5th March 2012