TDA5252G2 Datasheet, PDF (39/86 Pages) Infineon Technologies AG – ASK/FSK 915MHz Wireless Transceiver

Measured Magnitude of S11 of evalboard:
TDA5252 G2
Version 1.1
Application
S11_measured_915.pcx.
Figure 3-3 S11 measured
Above you can see the measured S11 of the evalboard. The –3dB-points are at 851MHz and
989MHz. So the 3dB-bandwidth is:
B = f_U − f _L = 989MHz − 851MHz = 138MHz
[3 – 1]
The loaded Q of the resonant circuit is:
Q_L =
f _center
B
= ^{915 MHz}
138 MHz
= 6.63
[3 – 2]
The unloaded Q of the resonant circuit is equal to the Q of the inductor due to its losses.
Q_U = Q_INDUCTOR ≈ 36@915MHz
[3 – 3]
An approximation of the losses of the input matching network can be made with the formula:
LOSS
=
−20*

log_1 −

Q_L
Q_U



=
−20 * log_{}1 −
6.63
36 ^
=
1,8dB
[3 – 4]
Data Sheet
39
2007-02-26