Basic definition

The filter is the passive four-terminal network, transmitting (or retenting) the defined frequency band.

Course of attenuating characteristic of the filter

Other terms and definitions

Title Symbol Definition
Nominal frequency fo [MHz] Indicates the nominal center frequency of the band-pass or the nominal stop frequency of a band-stop filter
Poles [–] The number of poles of the transfer function
Nominal bandwidth
(Pass band)
B1 [kHz] Minimal bandwidth of the pass-band at the attenuation A1 [dB]
Stop-bandwidth B2, B3 [kHz] Separation of frequencies between the relative attenuation of filter shall be equal to, or greater than, a specified value
Insertion loss L [dB] The logarithmic ratio of the power delivered to the load impedance before insertion of the filter to the power delivered to the load impedance after insertion of the filter
Pass-band ripple R [dB] Difference between the maximum value and the minimum value of attenuation within the pass-band B1 [kHz] of the filter
Alternate attenuation A3 [dB] Attenuation in a frequency range far outside of the pass band
Spurious response A4 [dB] Minimum attenuation caused by extraordinary response in the stop-band. Spurious response usually appears at higher frequency than the center frequency
Group delay distortion Δt [ µs ] The difference between the maximum and minimum group delay within the pass-band (B) unless otherwise specified
Terminating impedance Zt
Rt // Ct
[ Ω // pF ]
Either of the impedances presented to the filter by the source or by the load


For more information about the crystal filters can be obtained from the following technical standards:

EN (IEC) 60 368-1, Piezoelectric filters of assessed quality – Part 1: Generic specification