1. Uses of filters To remove unwanted components in a signal
To “shape” the spectrum of a complex wave
To determine spectra of complex waves

3. 100 Hz
1000 Hz
6000 Hz
20000 Hz
SIGNAL
FILTER
OUTPUT + =

4. Linear system Changes only amplitude of input components
Does not add additional components
No distortion

5. Nonlinear system Changes frequency along with amplitude
Introduces additional components not present in the input signal (frequency domain)
Harmonics
Combination tones
Introduces distortion (time domain)