2 SYSTEM DESCRIPTION
Inmarsat B
PAGE 2-5
9936
When a region shift search is performed, the satellite dish first turns to the direction 15° [45°] to the left (or
right, depending on which is closer) of the expected position of the satellite. From this point it performs a
horizontal search to the point 15° [45°] to the right (or left, if the start position was right) of the satellite. After
this, a ± 15° horizontal and ± 20° vertical fine search is performed around the point where the highest signal
strength was measured. The total region shift search will take 1-2 minutes.
2.1.6
TRACKING ALGORITHM
For long term optimisation of the antenna pointing reference a step-track algorithm is included in the control
system for the antenna. The basic concept of the tracking algorithm is to measure the signal level around
the current centre of pointing by moving the reference in small measurement steps. At each measurement
point the reference position is fixed during an averaging time which is long enough to cover one to several
sea wave periods. After the averaging period the mean level is interpreted as the tracking level for that
reference point. This measurement is repeated several times at equally spaced points on each side of the
centre point before a decision is taken in which direction to move the centre. This procedure is repeated
on the elevation and azimuth axes one at a time until a new search is started. The size of the measurement
steps on the azimuth axis increases when the elevation reference angle increases.
2.1.7
COMMUNICATION, SETUP AND STATUS SURVEILLANCE
In addition to antenna tracking and stabilisation the TSP controller works as the central control unit in the
ADE and takes care of various setup and control tasks in the ADE.
Control data communication with the BDE:
Receiver, transmitter and tracking receiver channels.
Search initiation and sky slice parameters.
Ship gyro compass information.
Transmitter power level.
Antenna status information.
HPA setup and error reporting:
The TSP communicates with the microcontroller in the HPA unit. Power level i n f o r -
mation, burst length information and transmitter frequency range are sent to the HPA.
Status information and error codes are received from the HPA and reflected to the BDE
whenever needed.
Synthesizer setup:
The three synthesizer groups in the antenna (up converter, down converter and tracking
receiver) are all programmed by the TSP with configuration and frequency information.
The frequency programming parameters are calculated by the TSP based on the
channel numbers received from the BDE. In addition the TSP surveys the lock signals
generated by the synthesizers to detect if a synthesizer is unlocked. Unexpected
unlock situations are reported to the BDE.
Содержание Inmarsat B
Страница 1: ...SAILOR Inmarsat B Workshop Manual W4400GB0 ...
Страница 2: ...Inmarsat B Workshop Manual 9905 ...
Страница 7: ...CONTENTS 1 INTRODUCTION 1 1 1 1 SYSTEM COMPONENTS 1 2 1 2 TECHNICAL DATA 1 2 9849 Inmarsat B ...
Страница 46: ...4 ACCESSORIES Inmarsat B PAGE 4 3 Inmarsat B 9849 Diagram Veritas connection box ...
Страница 124: ...CONTENTS 8 PERFORMANCE CHECK AFTER REPAIR 8 1 8 1 START UP SEQUENCE 8 1 9936 Inmarsat B ...
Страница 127: ...CONTENTS 9 SERVICE 9 1 9 1 CHECK OF OCXO 9 1 9936 Inmarsat B ...
Страница 129: ...CONTENTS 10 PARTS LISTS 10 1 9901 Inmarsat B ...
Страница 133: ...CONTENTS 11 ABBREVIATIONS 11 1 Inmarsat B 9849 ...