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PHYS3050 Lab 3
Filters
By: Aysar Khalid (209728866)
Lab Partner: Hassan Chehaitli
Submitted on: November 11
th
, 2010
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View Full Document Objective
The aim for this lab was to construct and analyze the properties of a lowpass filter.
In addition,
to understand how the power spectrum of sine, square, sawtooth, triangular wave and noise
are changed due to an RC filter.
3.1 The Fast Fourier Transform (FFT) Feature on the DSO
A 50 kHz sinusoidal signal was generated on the DSO.
The amplitude of the signal was
chosen to be 500 mV.
The options on the DSO were then set to MATH Menu > Operation FFT >
Window Hanning.
Operation FFT was set to allow us to see the Fast Fourier Transformation
(FFT) of each type of wave.
The window hanning allows for frequency calibration purposes.
The following are the observed power spectrum graphs for each wave type:
Note:
xaxis depicts frequency in kHz and yaxis depicts power in dB
Sine Wave
The power spectrum is accurate as the spike
seen is same at the fundamental frequency of
50 kHz. The graph also shows some noise.
Square Wave
Relatively even harmonic results can be seen
in the square wave spectrum.
Triangular Wave
Odd harmonic results can be seen in the
triangular wave spectrum.
SawTooth Wave
A duality of even and odd harmonic is seen in
the sawtooth wave spectrum.
Noise
White noise is a random signal (or process)
with a flat power spectral density i.e. the
signal contains equal power within a fixed
bandwidth at any center frequency.
According to the definition and by observing
the graph we can see that the signal contains
equal power within the fixed bandwidth and
hence this is white noise.
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View Full Document 3.2 The LowPass RC Filter, Part 1
In this part, we constructed an RC Filter circuit using a 1 nF capacitor and a 20 kOhm
resistor.
Its circuit diagram is shown below.
We choose a nonpolar capacitor because a non
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This note was uploaded on 12/11/2010 for the course PHYS 3050 taught by Professor Menary during the Fall '09 term at York University.
 Fall '09
 MENARY
 Power

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