tda5255e1 Infineon Technologies Corporation, tda5255e1 Datasheet - Page 39

• Manufacturer Part Number: tda5255e1
• Description: Ask/fsk 434mhz Wireless Transceiver
• Manufacturer: Infineon Technologies Corporation

Confidential
Measured Magnitude of S11 of evalboard:
Figure 3-3
Above you can see the measured S11 of the evalboard. The –3dB-points are at 404MHz and
468MHz. So the 3dB-bandwidth is:
The loaded Q of the resonant circuit is:
The unloaded Q of the resonant circuit is equal to the Q of the inductor due to its losses.
An approximation of the losses of the input matching network can be made with the formula:
Preliminary Specification
L
OSS
=
B
-
Q
20
=
Q
U
*
f
L
U
log
=
=
-
Q
S11 measured
é
ê
ê
ë
1
INDUCTOR
f
f
-
center
L
B
Q
Q
=
U
L
468
ù
ú
ú
û
=
=
»
-
MHz
434
20
32
64
*
2 ,
log
MHz
@
-
MHz
404
é
ê
ë
434
1
-
MHz
6
32
MHz
=
8 ,
ù
ú
û
6
8 ,
=
=
2
dB
64
MHz
39
[3 – 4]
[3 – 1]
[3 – 3]
[3 – 2]
TDA5255 E1
S11_measured_434.pcx.
Version 1.1
Application
2002-11-28