Bandpass Filter (BPF)

Band-pass Filter

This is a device that passes frequencies within a certain range and rejects frequencies outside of that range. Filter circuits can be designed by combining the properties of low-pass and high-pass into a single filter. This is called a band-pass filter.

(reference: https://www.allaboutcircuits.com/textbook/alternating-current/chpt-8/band-pass-filters/)

Parameters

(reference: http://info.ee.surrey.ac.uk/Teaching/Courses/ee1.cct/circuit-theory/section8/bandpass.html)

A band-pass filter has 5 characteristic parameters.

1. Center frequency

A frequency at which the transfer function is at a maximum

2. Cut-off frequency 1

A lower frequency at which the transfer function equals 1/root 2 of the maximum value

3. Cut-off frequency 2

A higher frequency where the transfer function equals 1/root 2 of the max value

4. Bandwidth

Width of the pass band

5. Quality factor

The ratio of the center frequency to the bandwidth. This gives a measure of the pass band and can be used to describe the shape of the transfer function graph.