Receivers; Receiver: Gsm900/1800 -Filter To Demodulator - Siemens C45 Repair Documentation

4.4 Receivers

4.4.1 Receiver: GSM900/1800 –Filter to Demodulator
From the antenna switch, up to the demodulator the received signal passes the
following blocks to get the demodulated baseband signals for the EGOLD+:
Filter >>>>>>>> LNA >>>>>>>> Demodulator>>>>>>>> PGC
Z880 Bright
Filter: The GSM900 and GSM 1800 filters are located inside the frontend module.
The Filter are centered to a frequency of 942,5MHz for GSM900 and 1847,5MHz
for GSM1800. The symmetrical filter output is matched via LC-Combinations to
the LNA input of the BRIGHT (D800)
LNA: The LNA´s is located inside the BRIGHT and is able to perform an
amplification/attenuation from ~ 20dB. The LNA is can be switched in HIGH and
LOW mode and is controlled by the Bright.
Demodulator: The Bright IC performs a direct demodulation of the received
GSM1900 Signals. To do so the LO1 is required.
The channel depending frequencies for 1900MHz band are divided by´2 for
internally.
PGC: After demodulation the "I" and "Q" signals are amplified by the internal
PGC-Amplifier whereby the "I" and the "Q" path are amplified independently
From each other. The performance of this PGC is 80dB (-22 up to 58dB),
switchable in steps of 2dB. The control is realised through the EGOLD+
signals (SYGCCL, SYGCDT,
After passing an internal switch, the signals are ready for further processing
through EGOLD+
The required voltage VCC_SYN
V1.0
C45, M50 AND MT50
Bright
SYNSTR).
is provided by the
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Bright
N840
ICM MP CCQ ST
05/02