Function: Keep the signals that need to be used, which we call valid signals, and suppress the signals that are not needed, which we call invalid signals.
Principle:
At present, cavity waveguide bandpass filters are mainly used. Its working principle is to induce a vibrator of the corresponding frequency through electromagnetic waves, usually a 5-level vibrator, and the signal attenuation is slightly larger.
The frequency point where the insertion loss of the filter is greater than 3dB is called the cut-off frequency of the filter. When the frequency exceeds the cut-off frequency, the filter enters the stop band, and in the stop band, the interference signal will be greatly attenuated. Determined according to the bandwidth of the effective signal, the cutoff frequency should be greater than the bandwidth of the signal, so as to ensure that the useful signal is not attenuated. According to the frequency of the interference signal, all the interference frequencies should fall within the stop band of the filter.
