tda5251f1 Infineon Technologies Corporation, tda5251f1 Datasheet - Page 39

• Manufacturer Part Number: tda5251f1
• Description: Ask/fsk 315mhz 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 288MHz and
344MHz. 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
LOSS
=
B
-
Q
20
=
Q
U
*
U f
L
log
=
=
Q
S11 measured
-
é
ê
ê
ë
1
INDUCTOR
-
f
f
center
L
Q
Q
B
=
U
L
344
ù
ú
ú
û
=
=
-
MHz
20
315
»
56
*
27
log
MHz
-
MHz
@
288
é
ê
ê
ë
1
315
-
MHz
5
27
=
MHz
6 ,
5
ù
ú
ú
û
6 ,
=
=
2
56
dB
MHz
39
[3 – 4]
[3 – 1]
[3 – 3]
[3 – 2]
TDA5251 F1
S11_measured_315.pcx.
Version 1.0
Application
2003-02-18