High Pass vs Low Pass Filters

Lowpass filter (smoothing)

A low pass filter is used to pass low-frequency signals. The strength of the signal is reduced and frequencies which are passed is higher than the cut-off frequency. The amount of strength reduced for each frequency depends on the design of the filter. Smoothing is low pass operation in the frequency domain.

Following are some lowpass filters:

1. Ideal Lowpass Filters

The ideal lowpass filter is used to cut off all the high-frequency components of Fourier transformation.

Below is the transfer function of an ideal lowpass filter.

2. Butterworth Lowpass Filters

Butterworth Lowpass Filter is used to remove high-frequency noise with very minimal loss of signal components.

3. Gaussian Lowpass Filters

The transfer function of Gaussian Lowpass filters is ahown below:

Highpass filters (sharpening)

A highpass filter is used for passing high frequencies but the strength of the frequency is lower as compared to cut off frequency. Sharpening is a highpass operation in the frequency domain. As lowpass filter, it also has standard forms such as Ideal highpass filter, Butterworth highpass filter, Gaussian highpass filter.