Frequency Generation; Discrete 13Mhz Vcxo - Siemens A35 Repair Documentation

4.2 Frequency generation

4.2.1 Synthesizer : The discrete VCXO (13MHz)
The Axx 13MHz signal is generated by a discrete VCXO. consisting of a colpitts
oscillator with a crystal
The subsequent oscillating circuit
create a de-coupling of the synthesiser from interference signals, coming from the
logic (SIN13M
(functional F13M)
The oscillator frequency is controlled by the EGOLD+
AFC_PNM signal, and the capacity diode V600, to ensure that the circuit is
working is stable conditions < 7,7ms after switching on the oscillator.
To reduce the charging time of the low pass
bridged by the diode V602.
For temperature control a temperature-dependent resistor
VCXO.
The required voltage VCC_SYN
The picture 4211 shows the signal at the collector of transistor V601_2.
S ig n a lfo r m
E G O L D +
V 1 .3
A F C
V1.0
A35-A36-A40
Z600 and a post-switched buffer stage as oscillator switch.
(C611,C619,
).
(R615,
is provided by the
1
1 2
R 1 0 6
A F C _ P N M
3 0 K
G N D
Page 7 of 38
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L600) and the resistor R611
generated
(functional R3)
C616) the resistor
R613 is placed near the
N431.
2
V 6 0 2
B A S 1 7 0 W
R 6 1 5 R 6 0 0
4 7 K 2 2 K
G N D
Notes
R615 is
3
3
G N D
4211
to SMARTI
to EGOLD+
ICM MP CC ST
09/01