29 Journey • Aliso Viejo, CA 92656 • USA
(949) 448-7070 • FAX: (949) 448-8484
E-MAIL:abinfo @abracon.com • INTERNET ADDRESS: www.abracon.com
ABRACON IS
ISO 9001 / QS 9000
CERTIFIED
CORPORATION
ABRACON
-66-
®
MONOLITHIC CRYSTAL FILTERS
TECHNICAL TERMS • TESTS • APPLICATIONS
TECHNICAL TERMS
Holder:
A case housing a thin piece of quartz crystal with vacu-
um-evaporated metal electrodes and terminals for connections.
Nominal Frequency:
Normally this refers to the nominal value
of the center frequency given in the specifications, to which
other frequencies may be referred. Nominal frequency usually
indicates the Center Frequency (Fo) and Carrier Frequency (Fc).
Pass Bandwidth:
The pass bandwidth in which the attenuation
is equal to or less than a specified value insertion loss.
Stop Bandwidth:
The stop bandwidth in which the attenuations
are equal to or greater than specified values in the stop band
attenuation.
Ripple:
The ripple (in pass band) is the difference between the
maximum and minimum attenuation within a passband.
Insertion Loss:
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.
Attenuation Bandwidth:
The frequency width at the value that
assures the relative attenuation is of the same value or higher
than the specified attenuation.
Attenuation Guaranteed:
The maximum attenuation guaran-
teed at the specified frequency range.
Termination Impedance:
Either of the impedance presented to
the filter by the source or by the load, and described the resistive
portion (Rt) and the parallel capacitive portion (Ct) including stray
capacitance.
Spurious Response:
Minimum attenuation caused by extra-
ordinary response in the stopband. Spurious response usually
appears at a frequency higher than the center frequency.
Group Delay distortion:
The difference between the maximum
and minimum group delay within pass bandwidth unless other-
wise specified.
Balanced Type and Unbalanced Type:
A balanced type is one
in which a pair of terminals is not connected to the case. An
unbalanced type is one in which one of a pair of terminals is con-
nected to the case.
Figure 1
CRYSTAL FILTERS TEST SET-UP
The termination impedance presented by the source or by the
load is either represented by a resistor and a capacitor (capaci-
tive type) or by a resistor and a “negative” capacitor (inductive
type). For a capacitive type, specified value of capacitor as given
in table can be used in the test circuit. For an inductive type
(“negative capacitance”), a L-C network is required to compen-
sate the negative capacitance.
TESTING CONFIGURATION
Two pole filters are cascaded to produce four, six, eight or more
pole filter responses with the addition of coupling capacities
between two pole sections.
APPLICATIONS
Crystal filters are widely used in mobile communications sys-
tems, mobile and cordless telephones, pagers and radios.
Abracon will manufacture crystal filters per custom specifica-
tions, including termination impedance, pass band width and at-
tenuation band width.
Figure 2
4 Pole MCF
Figure 3
4 Pole MCF
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