What is a Double Pole Filter?

Problem:
What is a Double Pole Filter?

Solution:
A Double Pole filter is a filter that rolls off frequencies in the stop band 40 dB per decade.

This is an example of a 10 kHz double pole low pass filter:



This is an example of a 10 kHz double pole high pass filter:



The pass band is the range of frequencies that are passed until the point is reached where the amplitude is rolled off 3 dB, or 70.7%. At ten times that frequency (for a low pass filter), and one tenth the frequency (for a high pass filter), the amplitude is rolled off 100 times, or 40 dB. Thereafter, the amplitude is rolled off 40 dB per decade of frequency.