Mixer, If-Amplifier And Demodulator - Siemens A35 Repair Documentation

4.4.2 Receiver : Mixer, IF Amplifier and Demodulator
The symmetrical LNA amplified EGSM900 and GSM1800 signals arrive at the
SMARTI pins 31,32,34,35,
To do so, the LO1 is guided via the SMARTI
Frequency calculation of the LO1: (Freq.GSM = RF+IF and Freq.PCN = RF-IF)
After mixing, the IF is filtered by an external SAW-Filter
SMARTI (input of the PGC-Amplifier).
The programmable PGC-Amplifier ensures an equalized level of the IF-Signal at the
input of the I/Q demodulator. To perform this, the PGC-Amplifier is switched
in 2 dB steps using the EGOLD+ signals (SYNSTR;SYGCDT;SYGCCL).
The demodulation is realised by the I/Q demodulator. To mix out the IF, the
nd
2 local oscillator frequency (1440MHz) divided by 4, is used.
Finally the "I" and "Q" signals are amplified and ready for further operations
through the GAIM part of the EGOLD+ (A/D conversion) as
at the SMARTI pins 1,3,4,48
The required voltage VCC2_8
4434
to
baseband
V1.0
A35-A36-A40
to be mixed down to the IF frequency of 360MHz..
pins 22,23
is provided by N430
4433
Page 13 of 38
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to the different mixers.
(Z500) to arrive again at the
RX_I,RX_IX-RX_Q,RX_QX
Notes
from LNA
ICM MP CC ST
09/01