Introduction - If you have any usage issues, please Google them yourself
When analyzing and processing signals, we often encounter the problem that useful signals are polluted by noise. Therefore, eliminating or reducing noise from signals has become a very important problem in signal transmission and processing. According to the different characteristics of useful signal and noise, the process of eliminating or weakening noise and extracting useful signal is called filtering. The system or device that realizes filtering function is called filter.
Classical filters are circuits with selective characteristics. When noise and useful signals have different frequency bands, they will be attenuated or even eliminated after passing through the filter, and useful signals can be retained.
When noise overlaps with the frequency band of useful signals, the above filters (or classical filters) can not achieve the function of both eliminating noise and retaining signals.