Radio Part - Siemens C75 Service Repair Documentation

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Copyright 2005© Siemens AG

4 Radio Part

The radio part is realizes the conversion of the GMSK-HF-signals from the antenna to the
baseband and vice versa.
In the receiving direction, the signals are split in the I- and Q-component and led to the D/A-
converter of the logic part. In the transmission direction, the GMSK-signal is generated in an
Up Conversion Modulation Phase Locked Loop by modulation of the I- and Q-signals which
were generated in the logic part. After that the signals are amplified in the power amplifier.
Transmitter and Receiver are never active at the same time. Simultaneous receiving in the
EGSM900 and GSM1800 band is impossible. Simultaneous transmission in the EGSM900
and GSM1800 band is impossible, too. However the monitoring band (monitoring timeslot) in
the TDMA-frame can be chosen independently of the receiving respectively the transmitting
band (RX- and TX timeslot of the band).
The RF-part is dimensioned for triple band operation (EGSM900, DCS1800, PCS19000)
supporting GPRS functionality up to multiclass 10.
The RF-circuit consists of the following components:
• Hitachi Bright 6E chip set (HD155165BP) with the following functionality:
o PLL for local oscillator LO1 and LO2 and TxVCO
o Integrated local oscillators LO1, LO2
o Integrated TxVCO
o Direct conversion receiver including LNA, DC-mixer, channel filtering and
PGC-amplifier
o 26 MHz reference oscillator
• Transmitter power amplifier with integrated power control circuitry
• Frontend-Module including RX-/TX-switch and EGSM900 / DCS1800 / PCS 1900
receiver SAW-filters
• Quartz and passive circuitry of the 26MHz VCXO reference oscillator
Service Repair Documentation
Level 2.5e – C75
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Release 1.0