Hopefully, a person could start using the MATLAB Continuous-Discrete Sampling
tool without any need to read these help files. Features were designed to be
intuitive and familiar to those with basic computer experience.
For those who like to read the manual, this section will give you the minimum
you need to get started and be comfortable with the use of the GUI.
First, if you have not already done so, follow the information given in the
Installation section to install and start the
MATLAB Continuous-Discrete Sampling tool.
- To begin with, set the input sinusoid's frequency f0
and phase. You can set the frequency f0 in
Hz by using the slider at the bottom-left of the GUI. Another way to
set the input frequency is, you can use the mouse to click and
drag the 'blue' stem plot corresponding to the Input signal in the
Continuous time spectrum (Plot axes at the bottom left). The phase of the
signal can be entered in the edit box below the text
Phase. You should be able to see the corresponding change in
Input, sampled signal x[n],
Output and the corresponding Spectrums.
- You can also set the sampling rate (fs in Hz)
at which the input needs to be sampled. This can be done using the slider at
bottom-right of the GUI.
- Instead of specifying the frequencies in Hz, the input frequency
and sampling rate can also be set in rad/s.i.e., w0 and ws, by toggling the
radio-button Rad/sec to 'ON'. Equivalently, you can achieve
the same, using the menu Plot Options: Show Radian
Frequency. This also toggles the frequency axis of input and output
spectrum plots between rad/s and Hz.
- If the sampling frequency selected is less than the Nyquist rate
(2f0), then you will see the text ALIASING! displayed in the output spectrum plot,
indicating the outputs have aliased.
- You can also toggle the frequency axis in the Discrete Time
Spectrum between the normalized cyclic frequency f or
normalized radian frequency w, using the Radian
radio-button.
- In the case of output being aliased, you can toggle the reference plot
overlying the Discrete time x[n] plot, to show either the
high-frequency or low-frequency aliased component. i.e. between the aliased
and un-aliased signals. This can be done using the menu, Plot Options:
Show Lower Frequency Signal or double-clicking on the x[n] plot
axes.
- Another useful feature of the Demo is its color-coded plots.
- If the frequency of the input signal lies within the range indicated by
the 'yellow' strip, then the output signal is not aliased.
- Un-aliased frequency components are marked in 'blue' and the aliased
components are marked in 'red', in the spectrum plots.
- When Aliasing occurs in the output signal, such that the original signal
cannot be reliably reconstructed, then the text ALIASING! is displayed in the output
Continuous Time Spectrum plot axes.
That's it! You now understand the basics of how to use the
MATLAB Continuous-Discrete Sampling tool; For a more in depth description of
Continuous-Discrete Sampling theory see the Theory section. The Controls and Menus sections provide a description of the various
elements in the user interface.