How band pass filter work

Nov 04, 2021

An ideal bandpass filter should have a completely flat passband, no amplification or attenuation in the passband, and all frequencies outside the passband are completely attenuated, in addition, the conversion outside the passband is extremely small The frequency range is complete.
In fact, there is no ideal bandpass filter. The filter cannot completely attenuate all frequencies outside the desired frequency range, especially there is a range that is attenuated but not isolated outside the desired passband. This is usually called the roll-off phenomenon of the filter, and is expressed in dB per decade of attenuation amplitude. Generally, the filter design should ensure that the roll-off range is as narrow as possible, so that the performance of the filter is closer to the design. However, as the roll-off range becomes smaller and smaller, the passband becomes no longer flat and "ripples" begin to appear. This phenomenon is especially obvious at the edge of the passband, and this effect is called the Gibbs phenomenon.

In addition to the fields of electronics and signal processing, an example of band-pass filter applications is in the field of atmospheric sciences. A very common example is to use band-pass filters to filter the weather data in the last 3 to 10 days. Only the cyclone as a disturbance remains in the domain.
The resonance frequency is between the lower cut frequency f1 and the higher cut frequency f2, where the gain of the filter is the largest, and the bandwidth of the filter is the difference between f2 and f1.
band pass filter

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