Objectives

1) To know how to generate a
square wave.

2) To investigate the
sampling process and the aliasing phenomena.

3) To learn how to use anti-alias
using Matlab.

Equipment Required

Sampling and aliasing

Sampling
is the process of converting a continuous time signal into discrete time
signal. As we know from the sampling theory, the sampling frequency must be at
least greater than twice the bandwidth of the analog signal as explained by the
sampling theory

Where is the
maximum frequency content of the analog signal.

In this
experiment a simple program for sampling a signal from the function generator
will be considered.

Part One: Basic sampling and
aliasing effects

1.
Write
a c program to read a signal from the LINE IN input of the DSK6713 and write
the data back to the line out. You can use the code shown in Figure 4to help you performing this task

1.
After
compiling and running your program, connect a signal from the function
generator to the LINE IN terminal

2.
Set
the function generator to sine wave, the amplitude of the signal to 1 V

_{PP}, and the frequency to 1 kHz and plot the signal as it appears on the screen of the oscilloscope
1.
Increase
the frequency of the square wave from 1 kHz to 4 kHz in steps of 1 kHz then
plot the signal as it appears on the oscilloscope. Explain the signal shape you
see on the screen of the oscilloscope repeat step 5 for sinusoidal signal

We
notice that when we increase the frequency of the signal, the period will
decrease according to the equation , until
we reach 4kHz. at 4 kHz aliasing will occur since the sampling frequency should
be and
after 4kHz the signal will disappear.

**Q1)**Determine the frequency of the reconstructed signal if the input signal frequency is and the sampling frequency is 8 kHz.

1.
Open
new MATLAB Simulink design

2.
Connect
the system as shown in Figure
7:

1.
Set
the frequency of the sine signal to 1 kHz with sampling frequency of 16 kHz.

2.
Set
the sampling frequency of DAC to 8kHz saturate mode.

3.
Choose
low pass filter with cut off frequency of the filter to 3.9 kHz and sampling
frequency 8 kHz .plot the signal as it appears on CRO.