Company Confidential s Com
Copyright 2005© Siemens AG
Page 8 of 37
Service Repair Documentation
Level 2.5e – C75
Release 1.0
4.3 Frequency generation
The C75 mobile is using a reference frequency of 26MHz. The generation of the 26MHz
signal is done via a VCO (Z950). TP (test point) of the 26MHz signal is the TP 820
The oscillator output signal 26MHz_RF is directly connected to the BRIGHT IC
(ball B9) to be
used as reference frequency inside the Bright (PLL). The signal leaves the Bright IC as
RF_SIN26M
(ball G9) to be further used from the SGOLDlite (D1000 (Functional AE15)).
VCXO Out
SGOLDlite In
Bright 6E
To compensate frequency drifts (e.g. caused by temperature) the oscillator frequency is
controlled by the (RF_AFC) signal, generated through the internal SGOLDlite (D1000
(A10))
PLL. Reference for the “EGOLD-PLL” is the base station frequency received via the
Frequency Correction Burst.
The required voltage VDD_RF2 is provided by the ASCI D1300
Waveform of the AFC_PNM signal from SGOLDlite to Oscillator
SGOLDlite
GND
GND
R2
RF_AFC
Signalform
C1
C2
AFC_PNM
GND
C3
R3
1 2 3
1
2
3
R1