V1.0 Page 7 of 38 ICM MP CC ST
A35-A36-A40 Company Confidential 09/01
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 Notes
oscillator with a crystal Z600 and a post-switched buffer stage as oscillator switch.
The subsequent oscillating circuit (C611,C619, L600) and the resistor R611
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+ (functional R3) generated
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 (R615, C616) the resistor R615 is
bridged by the diode V602.
For temperature control a temperature-dependent resistor R613 is placed near the
VCXO.
The required voltage VCC_SYN is provided by the N431.
The picture 4211 shows the signal at the collector of transistor V601_2.
EGOLD+
V1.3
GND
GND
47K
R615
AFC
Signalform
C110
To Next Page
Loading...
Need help?
General
