SAW Components
Data Sheet B3781
2
Feb 22, 2005
SAW Components
B3781
315,00 MHz
Low-loss Filter
Data Sheet
Features
s
RF low-loss filter for remote control receivers
s
Package for Surface Mounted Technology
(SMT)
s
Balanced and unbalanced operation possible
s
Passivation layer: Elpas
s
AEC-Q200 qualified component family
Terminals
s
Ni, gold plated
Pin configuration
1)
1
Input Ground (recommended) or Input
2
Input (recommended) or Input Ground
5
Output (recommended) or Output Ground
6
Output Ground (recommended) or Output
4,8
Case - Ground
3,7
to be grounded
Electrostactic Sensitive Device (ESD)
Type
Ordering code
Marking and package
according to
Packing
according to
B3781
B39321-B3781-Z810
C61157-A7-A46
F61074-V8167-Z000
Maximum ratings
Operable temperature range
T
A
45/+120
C
Storage temperature range
T
stg
45/+120
C
DC voltage
V
DC
6
V
Source power
P
S
10
dBm
source impedance 50
typ. dimensions in mm, approx. weight 0,07 g
Ceramic package QCC8B
1)
The recommended pin configuration usually offers best suppression of electrical crosstalk.The
filter characteristics refer to this configuration.
3
Feb 22, 2005
SAW Components
B3781
315,00 MHz
Low-loss Filter
Data Sheet
Characteristics
Reference temperature:
T
A
= 40 ... +85C
Terminating source impedance:
Z
S
= 50
and matching network
Terminating load impedance:
Z
L
= 50
and matching network
1)
Impedance for passband matching bases on an ideal, perfect matching of the SAW filter to
source- and to load impedance (here 50 Ohm). After the SAW filter is removed and input imped-
ance into the input matching / output matching network is calculated.
The conjugate complex value of these characteristic impedances are the input and output imped-
ances for flat passband. For more details, we refer to EPCOS application note #4.
min.
typ.
max.
Center frequency
f
C
--
315,00
--
MHz
(center frequency between 3 dB points)
Minimum insertion attenuation
min
including loss in matching elements
--
1,8
2,5
dB
excluding loss in matching elements
--
1,1
2,0
dB
Pass band (relative to
min
)
314,725... 315,275 MHz
--
0,9
3,0
dB
Filter bandwidth
rel
3
dB
0,69
0,76
0,83
MHz
Relative attenuation (relative to
min
)
rel
10,00 ... 294,50 MHz
47
51
--
dB
294,50 ... 304,50 MHz
42
46
--
dB
304,50 ... 312,80 MHz
21
28
--
dB
312,80 ... 313,20 MHz
33
40
--
dB
313,20 ... 314,30 MHz
6
9
--
dB
316,00 ... 323,00 MHz
10
14
--
dB
323,00 ... 335,00 MHz
34
40
--
dB
335,00 ... 600,00 MHz
43
48
--
dB
600,00 ...1000,00 MHz
60
70
--
dB
1000,00 ...2500,00 MHz
43
48
--
dB
Impedance for pass band matching
1)
Input:
Z
IN
=
R
IN
||
C
IN
--
410 || 2,6
--
|| pF
Output:
Z
OUT
=
R
OUT
||
C
OUT
--
410 || 2,6
--
|| pF
4
Feb 22, 2005
SAW Components
B3781
315,00 MHz
Low-loss Filter
Data Sheet
Matching network to 50
(element values depend on pcb layout and equivalent circuit)
C
p1
= 1,5 pF
L
s2
= 68 nH
L
s3
= 68 nH
C
p4
= 1,5 pF
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 QCC8B package, pinning 2,5 (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.
5
Feb 22, 2005
SAW Components
B3781
315,00 MHz
Low-loss Filter
Data Sheet
Frequency response
Frequency response (wideband)
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