Sample Quiz FIT9137 Modulation A
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Sample Quiz FIT9137
Modulation A
Encoding table
Symbol |
Frequency |
Amplitude |
Phase |
00 |
1Hz |
2 |
270 |
01 |
1Hz |
2 |
90 |
10 |
1Hz |
3.0 |
270 |
11 |
1Hz |
3.0 |
90 |
Note 1: Use the above encoding rules for all the tasks below.
Note 2: The phase values are in degrees.
Tasks:
1. Enter the coordinates of each symbol in your constellation diagram in the table below.
Only enter numerial values up to 2 decimal points. Any other character, except minus sign for negative values, will result in an incorrect answer.[8 Marks]
Symbol |
X |
Y |
||||
00 |
|
|
|
|
|
|
01 |
|
|
|
|
|
|
10 |
|
|
|
|
|
|
11 |
|
|
|
|
|
|
|
|
2. Draw a constellation diagram for the modulation scheme using Desmos. Enter the URL of your saved Desmos constellation diagram in the following field (for reference):
3. Draw a wave form for each symbol using Desmos. Place all the waveforms in the first period: [0-1]. Tip: a frequency of 1 Hz corresponds to 2πx in the sine wave formula. Enter the URL of your saved
Desmos symbols in the following field (for reference):
4. Sample the symbols specified in the table below at the given X coordinates (using the plots you
made in previous step). You can easily do this in Desmos: plot the symbol, then click on the curve and drag the mouse pointer around. Desmos will display the X and Y coordinate of the point on the curve. Move the cursor until the X coordinate matches the one given in the table. Record the Y coordinate
and enter it into the table. Enter only numeric values up to 2 decimal points. Any other character, except minus sign for negative values, will result in an incorrect answer. [16 Marks]
Symbol |
X |
Y |
||
00 |
0.3 |
|
|
|
0.7 |
|
|
|
|
01 |
0.3 |
|
|
|
0.7 |
|
|
|
|
10 |
0.3 |
|
|
|
0.7 |
|
|
|
|
|
11 |
0.3 |
|
|
|
0.7 |
|
|
|
|
|
5. Demodulate the following message (Figure 1). Remember that one symbol corresponds to one time unit (i.e., one unit on the X axis) since the frequency is 1 Hz. [4 Marks]
Figure 1 - Modulated message
Enter the demodulated message here:
You must enter the message as a simple sequence of 0 and 1, without spaces or commas between them (for example, 0001100100).
2023-10-17