Fourier (T212)

Subject Elec Eng

In this experiment you will explore sampling and the Fourier spectrums of signals. The equipment contains a rotating disc, photodiodes and red LEDs.

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OEL 2.3: Sampling and Fourier analysis

In this activity, you will experiment with sampling and the associated Fourier spectrums of signals created by passing infrared light through arc-shaped slots in a disc. This creates a square wave, since light is sensed for a short period of time (causing the signal to rise to 3.3 V), then no light is sensed for another short period of time (causing the signal to fall to 0.0 V). Because the disc is spinning at a constant speed, this creates rectangular waves.

You will first determine whether the rotational speed of the disc is indeed constant. Then you will experiment with the time‑voltage signal data transformed from the time domain into the frequency domain. In particular, you will try to identify the relevant harmonic frequencies for a square wave and reconstruct a time-domain signal from these frequency-domain data. Thus the challenge is to identify the harmonic frequencies associated with the signals, and to reconstruct the signals from these harmonics.

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