Sailor Inmarsat B, Workshop Manual

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3 MODULE DESCRIPTION Inmarsat B
PAGE 3-10 9901
3.1.10 SYNTHESIZER FOR UP/DOWN CONVERTER
The UP and DOWN converter synthesizers are two separate units but placed on the same printed circuit
board.
UP converter synthesizer
The two local oscillator signals used in the UP converter are generated on this synthesizer module. The
first local oscillator which is used to mix the transmitter frequency to first IF is named VHF synthesizer
and the other is named L-band synthesizer.
The frequency coverage of the two synthesizers are listed below:
L-band synthesizer: 1776.915 - 1810.620 MHz in steps of 315 kHz
VHF synthesizer: 213.0025 - 213.3150 MHz in steps of 2.5 kHz
A block diagram of the UP converter synthesizer is shown in fig. 3.10.
LOOP 1
PD :32 VCO
:N :64/65
:A
PD :63 VCO
:N
:A
:20/21
:A
:N :20/21
:64 PD VCO
VHF
L Band
Lock
det.
LOOP 2
10.08 MHz
from Triplexer
To TSP
from PLL
Lock Signals
35534
Fig. 3.10.