Lab sheet for Lab #1
Objective:
Use the oscilloscope to measure the spectrums of some common periodical signals.
Problems to solve before the lab session:
What is the Fourier transform of a rectangular pulse on [T/4, T/4] with amplitude 1?
Requirements:
1.
Each student should prepare a logbook to write report.
2.
Students should solve the problem before coming to the lab session.
3.
Two students work as a group in the lab.
4.
Each student submits a report to the lab in 24 hours after the lab session.
Equipments to be used:
1.
Signal generator
2.
Oscilloscope
Inlab activities:
1.
Review how to use the oscilloscope to inspect signals.
See the appendix on how to use the oscilloscope FFT functions.
2.
Go to the FFT interface.
Follow the steps for FFT in the appendix. Choose the rectangle window.
We will use this function to inspect the spectrum of some common periodic signals.
Spectrum is the frequency domain representation of a signal.
3.
The spectrum of a sinusoid of 50 KHz.
Input a sinusoid waveform of 50 KHz with 5V Vpp (peaktopeak voltage) from a signal
generator to Channel 1 by adjusting the signal generator. And observe the spectrum of this
sinusoid from the oscilloscope. You may need to adjust the oscilloscope parameters to get a
meaningful observation.
Sketch the sinusoid waveform and its spectrum in Fig.1.
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View Full DocumentFigure 1. FFT display for the sinusoid of 50 KHz
The Vpp of the time domain waveform:
The number of peaks on the spectrum:
The frequencies and amplitudes of the peaks:
Question 1:
How does the spectrum change when varying the frequency of this sinusoid?
4.
The spectrum of a square waveform with duty cycle 50%.
Duty cycle of a square waveform:
the ratio between the pulse duration to the pulse period.
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 Spring '11
 phoon
 Square wave, duty cycle, Fast Fourier transform, time domain waveform, square waveform

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