V1.0 Page 9 of 46 ICM MP CCQ ST
C45, M50 AND MT50 Company Confidential © Copyright Siemens AG 05/02
4.2 Frequency generation
4.2.1 Synthesizer: The discrete VCXO (26MHz)
M46 mobile is using a reference frequency of 26MHz for the Hitachi chip set.
The generation of the 26MHz signal is done via a discrete “Colpitts” VCXO .
This oscillator consists mainly of:
A 26MHz crystal Z950
An oscillator switch V950
A capacity diode V951
TP 951 after dividing by two
The oscillator output signal is directly connected to the BRIGHT IC (pin 38) to be
used as reference frequency inside the Bright and to be divided by 2.
This so gained signal SIN13MHZ_BB is used from the EGOLD+(functional M14).
To compensate frequency drifts (e.g. caused by temperature) the oscillator
frequency is controlled by the (AFC_PNM) signal, generated through the internal
EGOLD+ (D100 (functional R3)) PLL via the capacity diode V951.
Reference is the base station frequency.
To compensate a temperature caused frequency drift, the temperature-depending
resistor R959 is placed near the VCXO to measure the temperature. The
measurement result TVCXO is reported to the EGOLD+(baseband L4) via R136 as
the signal TENV.
The required voltage VCC_OSC is provided by the N840 (VCC_SYN) through
R863 and R861
Waveform of the AFC_PNM signal from EGOLD+ to Oscillator
EGOLD+
V1.3
GND
GND
47K
R615
AFC
Signalform
C110
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