Discrete Fourier Transform

Description| How it works| Gallery 1| Gallery 2

This is a powerful tool that will convert a given signal from the time domain to the frequency domain.


.xls file (43 KB) or .zip file (10 KB)

How to use

The use of this app is quite similar to the Function Calculus Tool. Key in the function that describes the signal into the cells B5 and the range into the cells B8 and B9. See this example screenshot for analysis of the function sin(x).

DFT Example

Once the entires are made, the tools shows 2 plots, the one on the top shows the "time domain" view and the one on the bottom shows the amplitudes of the various frequencies in the signal. The time domain plot also has red dots on it, these are the sampling points. The signal is sampled at 140 equidistant points over the range and the values at the sampled points used as inputs to the DFT calculation.

Note that for this app, selection of the range is important. Incorrect sampling can cause DFT leakage (the example screen shot exhibits this) or aliasing. According to the Shannon's Sampling theorem, a continuous function must be discretely sampled at at least twice the frequency of the highest frequency in the signal.

Also See:

Bode Plot Generator

Laplace to Time Domain Converter

Image Processing

Filter Analysis and Simulation

FIR Filter Analysis