[link] shows the front panel of the touch-tone telephone system. When the program is run, one can hear the dial tone and see the signal displayed in the upper waveform graph. As soon as any number key is pressed, the dial tone is stopped and the corresponding key pad tone is heard and displayed. When keys are pressed 10 times (a valid phone number), the system plays the ringing tone or busy tone depending on the setting and displays the tone in the lower waveform graph.
Lab exercises
Dithering
Dithering is a method of decreasing the distortion of a low-frequency signal due to signal digitization
[link] . Dithering works best when the sample rate is high in comparison with the rate at which the signal changes.
To see how this works, consider a slowly varying signal and its digitization, shown in
[link] (a). If noise is added to the original signal amplitude roughly at one half the step size, the signal will look like
[link] (b). If the digitized signal is passed through a resistor-capacitor circuit to smooth it out, an approximation to the original signal can be recovered. There is no theoretical limit to the accuracy possible with this method as long as the sampling rate is high enough.
Design a system to analyze the dithering technique. First, show the digitized and smoothed signal without dithering. Then, add random noise to the input signal (noise level should not exceed 50 percent of the step size of the digitized signal) and show the digitized and smoothed version. Measure the maximum and average error between the original signal and recovered signal.
Insert Solution Text Here
Image Processing
DFT is widely used in image processing for edge detection. A digital image is a two-dimensional signal that can get stored and processed as a two-dimensional (2D) array. In the frequency domain, with the center denoting (0,0) frequency, the center portion of this 2D array contains the low-frequency components of the 2D signal or image. The edges in the image can be extracted by removing the low-frequency components.
Read and display the image file
image1.jpg provided on the book website. Then, complete the following steps:
Compute and display the 2D DFT of the image using the LabVIEW MathScript functions
fft2 and
fftshift .
Remove the low-frequency components of the image. A user-controlled threshold can be specified to remove a varying amount of the low-frequency components.
Compute and display the inverse 2D DFT of the image using the LabVIEW MathScript functions
ifft2 and
fftshift . The processed image should reflect the edges in the original image.
Insert Solution Text Here
DTMF Decoder
Design a decoder VI for the DTMF system described in Telephone Signal section. The VI should be capable of reading the touchtone signal as its input and display the corresponding decoded key number as its output.
the study of living organisms and their interactions with one another and their environment.
Wine
discuss the biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles in an essay form
advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
Abdullahi
cell theory state that every organisms composed of one or more cell,cell is the basic unit of life
Abdullahi
is like gone fail us
DENG
cells is the basic structure and functions of all living things
A scanning electron microscope (SEM) is ideal for situations requiring high-resolution imaging of surfaces. It is commonly used in materials science, biology, and geology to examine the topography and composition of samples at a nanoscale level. SEM is particularly useful for studying fine details,
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Source:
OpenStax, An interactive approach to signals and systems laboratory. OpenStax CNX. Sep 06, 2012 Download for free at http://cnx.org/content/col10667/1.14
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