Monolythic Crystal Filters
Filter Characteristics
Critical to the understanding of filter behavior is a definition of the vocabulary of the
most frequently used terms and familiarity with the typical filter amplitude frequency
response curve, (fig. 1).
Center Frequency (F0)
– The frequency between the high and low cut off frequencies
of a filter.
Bandwith (BW)
– The difference between two cut off frequencies at a specified
attenuation level (3dB or 6dB).
Attenuation
– Reduction of signal in transmission through a filter.
(Attenuation is usually indicated in decibels dB).
Decibel
– Unit that shows the ratio between two powers, two voltages or two currents.
Insertion Loss
– Power loss of the filter in the passband (in dB). Zero dB reference
shall be the point of maximum output of the filter unless it is specified otherwise.
Termination Impedance
– A value to terminate the filter input/output. It is generally
expressed by resistance with parallel to capacitance which contains stray capacitance.
Insertion Loss = 10 Log Pin
Pout
Load Impedance
(Output termination) – The impedance connected to the output
terminals of the filter in order to achieve the proper response.
Spurious Mode
– Unwanted responses that occur in the filter due to resonant
frequncies of the crystal other than the fundamental frequency.
(10 Log P
1
, 20 Log V
1
or 20 Log I
1
)
V
2
P
2
I
2
Shape Factor
– Ratio of bandwidths at two different levels of attenuation.
Ripple
– Is the difference between the passband maximum value and minimum loss.
FREQUENCY IN KHz
190
0
3dB
10
F
1
PASSBAND
BANDWIDTH
EQUALS F
2
-F
1
BW
1
F
2
RIPPLE
F
0
=
F
2
+ F
1
2
200
210
220
INSERTION LOSS
230
ATTENUATION (DECIBELS)
20
30
40
STOPBAND
BW
2
SPURIOUS
RESPONSE
50
SHAPE FACTOR
60
ATTENUATION
PEAK
70
BW
2
BW
1
fo
The pulse of progress
Monolythic Crystal Filters
type
10K7A
10K7.5A
10K15A
10K6B
10K7.5B
10K7.5B1
10K15B
21K15A
21K7.5B
21K15B1
center Fr
(MHz)
10.695
10.700
10.700
10.700
10.700
10.695
10.700
21.400
21.400
21.400
No. of
poles
2
2
2
4
4
4
4
2
4
4
holder
type
49U or 49T
49T
49T
2 x 49T
2 x 49T
2 x 49T
2 x 49T
UM1 or UM5
2x(UM1 or UM5)
passband
width (min)
6 dB ± 3.5 KHz
3 dB ± 7.5 KHz
3 dB ± 3.0 KHz
stopband
width(max)
20 dB ± 10 KHz
18 dB ± 25 KHz
40 dB ± 10 KHz
insertion
loss (max)
2 dB
2 dB
2 dB
3 dB
2 dB
2 dB
2 dB
2 dB
2 dB
2 dB
passband
coupling
ripple (max) capacitance
-
1 dB
1 dB
1 dB
1 dB
1 dB
1 dB
1 dB
1 dB
1 dB
-
-
-
24 pF
15 pF
15 pF
5.5 pF
-
20 pF
5 pF
termination
impedance
1 kΩ//11.5 pF
1.5 kΩ//5.5 pF
3 kΩ//2.5 pF
1 kΩ//8.5 pF
1.5 kΩ//3.5 pF
1.5 kΩ//3.5 pF
3 kΩ//1.5 pF
1.5 kΩ//3.5 pF
900Ω//5.4 pF
1.5 kΩ//2.5 pF
3 dB ± 3.75 KHz 18 dB ± 12.5 KHz
3 dB ± 3.75 KHz 40 dB ± 12.5 KHz
3 dB ± 3.75 KHz 40 dB ± 12.5 KHz
3 dB ± 7.5 KHz
3 dB ± 7.5 KHz
3 dB ± 7.5 KHz
40 dB ± 25 KHz
18 dB ± 25 KHz
40 dB ± 14 KHz
40 dB ± 25 KHz
2x(UM1 or UM5) 3 dB ± 3.75 KHz
HC49/U
Resistance Weld
11.1 max.
HC49/T
Resistance Weld
11.1 max.
UM1
Resistance Weld
UM5
Resistance Weld
7.8 max.
13.5 max.
7.8 max.
11.20 max.
8.0 max.
5.8 max.
3.1 max.
ø 0.35
3.1 max.
3.75
±0.2
12.7 min.
20.0 min.
20.0 min.
4.65 max.
4.65 max.
4.88
±0.2
4.88
±0.2
3.1 max.
4.7 max.
4.7 max.
ø 0.43
ø 0.43
in mm
in mm
in mm
in mm
The pulse of progress
Filters
ø 0.35
3.1 max.
3.75
±0.2
12.7 min.
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