Sampling and Nyquist in PCM
PCM modulation: is a kind of source coding which is a conversion of a signal from analog to digital.The Nyquist theorem states that a signal must be sampled at a rate greater than twice the highest frequency component of the signal to accurately reconstruct the waveform. read more...
To perform the Experiment please follow the procedure:
1. Install the run time engine program to operate each VI.
2. Activate
the
functions generator,
scope,
and
DSA
by pressing
the
from
the tool bar, and then press the
in
each.
3. Adjust the function generator using its soft controls for an output with the following specifications.
|
Wave Form Shape |
Sinusoidal |
|
Frequency |
2 KHz |
|
Amplitude |
4 Vp-p |
4. Adjust the scope as follows:
|
Channel 0 |
Channel 1 |
|
|
Volts/Div |
1 V |
1 V |
|
DC offset |
0 V |
0 V |
|
Time/Div |
200 µ sec | 200 µ sec |
5. Set the values for the DSA as follows:
|
Input Settings |
Source Channel to Channel 1 |
|
FFT Settings |
Frequency span to 45,000 |
|
Resolution to 400 |
|
|
Windows to 7 term B-Harris |
|
|
Trigger Settings |
Edge |
|
Frequency Display |
Units to dB |
|
Mode to RMS |
|
|
Scale to Auto |
|
|
Voltage Range to ±10 V |
|
|
Averaging |
Mode to RMS |
|
Weighting to exponential |
|
|
# of averages to 3 |
6. Run the oscilloscope at Ch (0) and take a screen shoot for the input signal.
7. Record Vp-p:
8. Run the dynamic signal analyzer and take a screen shoot for the input power signal.
9. Determine the power signal for the input signal in dBVrms value at:
|
Frequency (Hz) |
Power dBVrms |
|
15K |
|
|
20K |
|
|
25K |
|
|
30K |
|
|
35K |
|
10. Change to the Ch1(output) and take a screen shoot for the output signal:
11. Record Voutp-p:
12. Take a screen shoot for the output power signal:
13. Determine the output power signal in dDVrms at value:
|
Frequency (Hz) |
Power dBVrms |
|
15K |
|
|
20K |
|
|
25K |
|
|
30K |
|
|
35K |
|
14. Take a screen shoot for the input and the output signal (ch0, ch1) dual.
15. Determine the frequency of the first six aliases in the sampled message.
1.
2.
3.
4.
5.
6.
16. Take a screen shoot for the first aliasing waveform.