Siemens A55 Repair Documentation

V1.20 Page 13 of 48 ICM MP CCQ GRM
A55/C55_Hitachi Company Confidential © Copyright Siemens AG 04/03
4.3 Antenna switch (electrical/mechanical only C55)
Internal/External <> GSM1800/900 <> Receiver/Transmitter
The C55 mobile has two antenna switches. A55 has no external antenna
connector/mechanical antenna switch.
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 A55/C55 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+
a) Internal/External antenna switch
to / from
di
p
lexe
r
Internal
to EGOLD
External

Siemens A55 Specifications

General

Brand	Siemens
Model	A55
Category	Cell Phone
Language	English