SAW Components
SAW filter
Short range devices
Series/type:
Ordering code:
Date:
Version:
B3949
B39921B3949H110
January 13, 2014
2.0
©
EPCOS AG 2014. Reproduction, publication and dissemination of this data sheet, enclosures
hereto and the information contained therein without EPCOS’ prior express consent is prohibited.
SAW Components
SAW filter
Data sheet
Application
s
Low-loss RF filter for remote control receivers
s
Balanced and unbalanced operation possible
B3949
921.42 MHz
Features
s
s
s
s
s
s
s
s
s
s
Package size 3.0 x 3.0 x 1.0 mm
3
Package code DCC6E
RoHS compatible
Approximate weight 0.037 g
Package for
Surface Mount Technology
(SMT)
Ni, gold-plated terminals
Lead free soldering compatible with J - STD20C
Passivation layer Elpas
AEC-Q200 qualified component family
Electrostatic Sensitive Device
(ESD)
Pin configuration
1)
s
s
s
s
s
1
2
4
5
3,6
Input (recommended) or input ground
Input ground (recommended) or input
Output (recommended) or output ground
Output ground (recommended) or output
to be grounded
1) The recommended pin configuration usually offers best
suppression of electrical crosstalk. The filter characteris-
tics refer to this configuration.
Please read
cautions and warnings and
important notes
at the end of this document.
2
January 13, 2014
SAW Components
SAW filter
Data sheet
Characteristics
Temperature range for specification:
Terminating source impedance:
Terminating load impedance:
T = –40 ˚C to +85 ˚C
Z
S
= 50
Ω
and matching network
Z
L
= 50
Ω
and matching network
min.
Center frequency
Minimum insertion attenuation
incl. loss in matching elements (Q
L
=65)
excl. loss in matching elements
Pass band (relative to
α
min
)
921.27 ... 921.57 MHz
Relative attenuation (relative to
α
min
)
α
rel
10.00 ... 800.00 MHz
800.00 ... 887.00 MHz
887.00 ... 896.00 MHz
896.00 ... 919.00 MHz
924.00
928.00
940.00
950.00
...
...
...
...
928.00
940.00
950.00
1000.00
MHz
MHz
MHz
MHz
f
C
α
min
—
—
3.4
3.2
3.8
3.6
—
typ.
@ 25 ˚C
921.42
max.
—
B3949
921.42 MHz
MHz
dB
dB
—
0.5
1.0
dB
50
44
38
21
12
20
36
42
57
50
44
27
17
25
42
47
—
—
—
—
—
—
—
—
dB
dB
dB
dB
dB
dB
dB
dB
Impedance
for pass band matching
1)
Input: Z
IN
= R
IN
|| C
IN
Output: Z
OUT
= R
OUT
|| C
OUT
1)
—
—
260 || 1.6
270 || 1.3
—
—
Ω
|| pF
Ω
|| pF
Impedance for passband matching bases on an ideal, perfect matching of the SAW filter to source- and to load
impedance (here 50 Ohm). After removal of the SAW filter the input impedance of the input and output match-
ing network is calculated. The conjugate complex value of these characteristic impedances are the input and
output impedances for flat passband. For more details we refer to EPCOS application note #18.
Please read
cautions and warnings and
important notes
at the end of this document.
3
January 13, 2014
SAW Components
SAW filter
Data sheet
B3949
921.42 MHz
Maximum ratings
Operable temperature range T
Storage temperature range
DC voltage
Source power
T
stg
V
DC
P
S
–45/+125 ˚C
–45/+125 ˚C
6
V
10
dBm
source impedance 50
Ω
Please read
cautions and warnings and
important notes
at the end of this document.
4
January 13, 2014
SAW Components
SAW filter
Data sheet
Matching network to 50
Ω
(element values depend on pcb layout and equivalent circuit)
C
p1
= 2.7 pF
L
s2
= 15 nH
L
s3
= 15 nH
C
p4
= 2.2 pF
B3949
921.42 MHz
Minimising the crosstalk
For a good ultimate rejection a low crosstalk is necessary. Low crosstalk can be realised with a good
RF layout. The major crosstalk mechanism is caused by the “ground-loop” problem.
Grounding loops are created if input-and output transducer GND are connected on the top-side of
the PCB and fed to the system grounding plane by a common via hole. To avoid the common
ground path, the ground pin of the input- and output transducer are fed to the system ground plane
(bottom PCB plane) by their own via hole. The transducers’ grounding pins should be isolated from
the upper grounding plane.
A common GND inductivity of 0.5nH degrades the ultimate rejection (crosstalk) by 20dB.
The optimised PCB layout, including matching network for transformation to 50 Ohm, is shown
here. In this PCB layout the grounding loops are minimised to realise good ultimate rejection
Optimised PCB layout for SAW filters in DCC6E package, pinning 1,4 (top side, scale 1:1)
The bottom side is a copper plane (system ground area). The input and output grounding pins are
isolated and connected to the common ground by separated via holes.
For good contact of the upper grounding area with the lower side it is necessary to place enough
via holes.
Please read
cautions and warnings and
important notes
at the end of this document.
5
January 13, 2014
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