Ten basic concepts of RF filter are as follows:
Attenuation: the amplitude loss of a signal after passing through the RF filter, usually expressed in decibels (DB).
Cut off frequency point: it is generally considered to be the point where the frequency response of the filter decreases by 3 dB.
Group delay: filter phase parameter relative to frequency. Measured by the group delay time (seconds), it can be considered as the propagation time delay of the signal envelope when the amplitude modulated signal passes through the RF filter.
Insertion loss: loss of signal power due to component insertion.
Isolation: to prevent accidental interaction between signals (e.g., transceiver interaction), isolate two signals from each other.
Quality factor: the quality factor is a measurement standard for the selectivity of resonant circuit, which is expressed as the ratio of stored energy to lost energy in each reciprocating cycle.
Passband: the area through which the signal passes relatively without attenuation.
Ripple: the change of insertion loss in the passband region.
Selectivity: a measure of the ability of a filter to pass or suppress a specific frequency (relative to the center frequency of the filter). Generally, the degree of selectivity is expressed as the loss occurring at some specific frequency difference relative to the center frequency of the filter when the signal passes through the filter.
Stopband: the band in which the filter reaches the specified out of band suppression frequency, expressed in decibels.