# Fourier filter

This document allows you to perform online Fourier filtering using an example of a signal consisting of two parts simulating pre-emergency and emergency modes. The pre-emergency mode is modeled by a sinusoidal signal, the emergency mode is modeled by a sinusoidal signal and an exponent. You can see the essence of the Fourier transform here. Instructions for using the Fourier filter are given here.

##### Input signal:

Pre-emergency mode:
Pre-emergency duration: ms
Signal: i(t) = · sin(2π··t + °)

Emergency mode:
Emergency duration: ms
Signal: i(t) = · sin(2π··t + °) + exp(-·t)

Fourier filter options:
Frequency of filter: Hz
Sampling frequency: Hz