Siemens S55 - Antenna Switch (Electrical;Mechanical)

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S55/S57 Company Confidential © Copyright Siemens AG 12/02
4.3 Antenna switch (electrical/mechanical)
Internal/External <> EGSM900/GSM1800/GSM1900 <> Receiver/Transmitter
The S55/S57 mobile has two antenna switches.
a) The mechanical antenna switch for the differentiation between the internal and
external antenna
b) The electrical antenna switch, for the differentiation between the receiving and
transmitting signals.
To activate the correct settings of this diplexer, the EGOLD+ signals RF_SW
and TXON_GSM are required
As a new feature the S55/S57 has an integrated “SAR detection” circuit. This circuit is
used to decide if the internal antenna or an external antenna is used. The goal is, to
reduce the transmit power when the internal antenna is used and the mobile is held
very close to the body. On the other hand, the mobile can send with more power, if the
external antenna is used. This distinction is done by the SAR detection circuit which
consists of the voltage divider R872 and R873. The ANT_DET output provides a high
level when the external antenna is used. ANT_DET
(Serial Interface L16) is connected to
the EGOLD+. Required voltage is VCC_ANT_DET (VCC2_8 via R892)
a) Internal/External antenna switch
to / from
di
p
lexe
r
Internal
to EGOLD
External
Sheet 1
near TXVCO