Sailor Inmarsat B Workshop Manual

SAILOR

Inmarsat B

Workshop Manual

W4400GB0

Inmarsat B

Workshop Manual

9905

9936

Please note

Any responsibility or liability for loss or damage in connection with the use of this product and the

accompanying documentation is disclaimed.

The information in this manual is furnished for informational use only, is subject to change without notice,

may contain errors or inaccuracies, and represents no commitment whatsoever.

This agreement is governed by the laws of Denmark.

Doc.no.: W4400GB0 Issue: D/9936

9936

CONTENTS

1 INTRODUCTION 1-1

1.1 SYSTEM COMPONENTS 1-2

1.2 TECHNICAL DATA 1-2

2 SYSTEM DESCRIPTION 2-1

2.1 ABOVE DECK EQUIPMENT 2-1

2.2 BELOW DECK EQUIPMENT 2-6

3 MODULE DESCRIPTION 3-1

3.1 ABOVE DECK EQUIPMENT 3-1

3.2 BELOW DECK EQUIPMENT 3-16

4 ACCESSORIES 4-1

4.1 SC4350 CONTROL UNIT 4-1

4.2 SD4360 DISTRESS BUTTON 4-1

4.3 H4394/95 VERITAS CONNECTION BOX 4-2

4.4 H4396 T-CONNECTION BOX 4-2

5 DISASSEMBLING, CONNECTORS, MODULE AND

SOFTWARE LOCATION 5-1

5.1 ANTENNA UNIT 5-1

5.2 TRANSCEIVER UNIT 5-17

5.3 HANDSET 5-25

5.4 CONTROL UNIT 5-25

6 SERVICE INTERFACE 6-1

6.1 ADE 6-2

6.2 ALARM 6-4

6.3 BOOK 6-4

6.4 BUTTONS 6-5

6.5 CAN 6-5

6.6 CASC 6-5

6.7 COURSE 6-7

6.8 CU 6-7

6.9 DATE 6-9

6.10 EXIT 6-10

6.11 GYRO 6-10

6.12 HELP 6-10

6.13 LES 6-11

6.14 LOG 6-11

6.15 MODEM 6-12

6.16 NUMERIC 6-13

6.17 PAX 6-13

6.18 POSITION 6-14

6.19 PRINTER 6-14

6.20 REGION 6-15

6.21 REMARK 6-16

6.22 SES 6-16

6.23 SNU 6-17

Inmarsat B

CONTENTS Inmarsat B

6.24 SPEED 6-18

6.25 SPS 6-18

6.26 STATUS 6-19

6.27 SU 6-20

6.28 TEST 6-20

6.29 TIME 6-22

6.30 VDP 6-23

6.31 VERSION 6-23

7 TROUBLE SHOOTING 7-1

7.1 BATTERY BACKUP 7-1

7.2 REAL-TIME CLOCK 7-1

7.3 EEPROM 7-1

7.4 INMARSAT IDs 7-2

7.5 +15V DC 7-2

7.6 FACTORY RESET 7-2

7.7 TX INHIBIT 7-2

7.8 DISTRESS BUTTON 1 7-3

7.9 DISTRESS BUTTON 2 7-3

7.10 TELEX INPUT 7-3

7.11 PRINTER INPUT 7-4

7.12 ADE INPUT 7-4

7.13 NMEA POSITION INPUT 7-5

7.14 SERVICE INPUT 7-5

7.15 NMEA GYRO INPUT 7-5

7.16 PRINTER ON-LINE 7-6

7.17 HEADING KNOWN 7-6

7.18 POSITION KNOWN 7-6

7.19 OCEAN REGION VALID 7-7

7.20 CONTROL UNIT FOUND 7-7

7.21 SCANBUS DATA TRANSMISSION 7-7

7.22 SCANBUS DATA RECEPTION 7-7

7.23 TU BUS 7-8

7.24 MODEM FOUND 7-8

7.25 MODEM ACTIVE 7-8

7.26 MODEM RX SU RATIO 7-9

7.27 SPS FOUND 7-9

7.28 SPS RX IF 7-9

7.29 SPS RX FILTER 7-9

7.30 SPS TX IF 7-10

7.31 SPS TX FILTER 7-10

7.32 SPS DSP 7-10

7.33 SPS OCXO 7-11

7.34 SPS RX S/N RATIO 7-11

7.35 ADE FOUND 7-11

7.36 DOWN CONVERTER LOCKED 7-12

7.37 TRACKING RECEIVER LOCKED 7-12

7.38 UP CONVERTER LOCKED 7-12

7.39 HPA FAILED 7-13

7.40 HPA TIMED OUT 7-13

7.41 HPA STOPPED 7-13

7.42 ADE READY 7-14

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CONTENTS Inmarsat B

9936

7.43 ADE IDLE 7-14

7.44 ANTENNA DIRECTION 7-14

7.45 ADE AZIMUTH RATE SENSOR 7-15

7.46 ADE ELEVATION RATE SENSOR 7-15

7.47 ADE CROSS-ELEVATION RATE SENSOR 7-15

7.48 ADE INCLINOMETER 7-16

7.49 ADE CONNECTION STABILITY 7-16

7.50 VDP RUNNING 7-17

7.51 VDP MODEM DETECTED 7-17

7.52 VDP CLOCK DETECTED 7-17

7.53 PAX FOUND 7-18

7.54 PAX RUNNING 7-18

7.55 PAX PHONE 1 ACTIVITY 7-18

7.56 PAX PHONE 2 ACTIVITY 7-19

7.57 PAX PHONE 1 PABX SETTING 7-19

7.58 PAX PHONE 2 PABX SETTING 7-19

7.59 PAX PHONE 1 LINE NOISE 7-20

7.60 PAX PHONE 2 LINE NOISE 7-20

7.61 SPS OCXO WARM 7-20

7.62 ADE FAILED 7-21

7.63 ADE CONTROL INPUT 7-21

7.64 ADE CONTROL OUTPUT 7-21

8 PERFORMANCE CHECK AFTER REPAIR 8-1

8.1 START-UP SEQUENCE 8-1

9 SERVICE 9-1

9.1 CHECK OF OCXO 9-1

10 PARTS LISTS 10-1

11 ABBREVIATIONS 11-1

CONTENTS

1 INTRODUCTION 1-1

1.1 SYSTEM COMPONENTS 1-2

1.2 TECHNICAL DATA 1-2

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1 INTRODUCTION

This manual describes the technical aspects of the Inmarsat B terminal. The purpose of the manual is

to provide the service technician with the knowledge about the system needed to locate faults and carry

out repair and performance checks after repair.

The contents of this manual have been structured as follows.

This chapter contains a brief description of the units of which a terminal consists, including accessories.

At the end of this chapter, technical specifications are listed.

Chapter 2 describes the system concept concerning antenna platform, its stabilisation and RF signal path

and finally the transceiver unit.

Chapter 3 is a technical description of the modules of which the antenna and transceiver unit consist.

Chapter 4 is a technical description of the accessories.

Chapter 5 concerns disassembling, connectors, module and software location.

Chapter 6 is a description of the commands in the service interface program, a software program which

is helpful during installation and trouble shooting.

Chapter 7 is a more detailed description of the self-test command and its use in locating faults.

Chapter 8 concerns performance checks after repair.

Chapter 9 describes preventive maintenance and how to adjust the system reference oscillator.

Chapter 10 contains the parts lists.

Chapter 11 is a list of the abbreviations used in this manual.

Note:

All descriptions of the ADE especially the ADE search are valid from ADE/TSP SW version 2.3.0 only.

1 INTRODUCTION Inmarsat B

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1.1 SYSTEM COMPONENTS

An Inmarsat B terminal can be supplied with various types of service and accessories. The drawing below

shows an installation with the various types of accessories.

ADE: The ADE (Above Deck Equipment) consists of a stabilised platform pointing the

antenna towards the satellite independent of the motion of the ship. Besides the

stabilisation including motors, sensors, tracking and stabilisation processor, the

platform also contains the main part of the RF equipment.

BDE: In the BDE (Below Deck Equipment) are placed the first/last part of the transmitter/

receiver consisting of a baseband UP and DOWN converter. Besides the interface

circuits for the various types of externally connected equipment, the BDE also

contains the signal processing, i.e. error correcting coding/decoding, voice coding/

decoding etc.

Handset: The control handset SC4345 is an integrated handset with display and keyboard used

when a voice call is in progress. A call is set up by entering the phone number from

the handset keyboard. A voice distress call can be started by removing the handset

from the hook and activating the distress button placed in the hook. Another function

of the handset is to use it as a control and set-up unit, where functions like the selection

of coast station and satellite can be carried out.

Control unit: The control unit SC4350 is a desk/bulkhead mounted keyboard and display with an

additional handset without keyboard and display.

Distress button: The distress button can be used to activate a voice or a telex distress alert. The kind

of distress alert the button is used for is selected during installation.

Connection

box: If there is a need for the connection of more than one handset or control unit, the

connection box is used. A maximum of five handsets or control units can be connected

to one transceiver unit which is possible by using four connection boxes.

Veritas: The Veritas connection box can be used as an interconnection box between the

transceiver unit and other system units using ship installation cables. Cables of that

type cannot be connected directly to the relatively small SUB-D connectors at the rear

panel of the transceiver unit.

Inside the Veritas connection box, to interface with ship installation cables, there is a

single printed circuit board containing SUB-D connectors to interface with the

transceiver unit and wire terminal blocks. Besides interfacing between transceiver

unit and ship installations, a gyro repeater is also included. The gyro repeater can be

used if there is no NMEA signal from the gyro of the ship.

1 INTRODUCTION Inmarsat B

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Inmarsat B

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SAT-B TRANSCEIVER

S.P. RADIO DENMARK

PABX Connection or

Push Button Telephone

32213E

Gyro NMEA

GPS NMEA

PABX

Heading Information

56/64 Kbit/sec.

Async./Sync.

Position Information

Personal

Computer

Heading Information

or Gyro

Distress Key

SD4360

Transceiver ST4425 Power Cable DC 24V

Compass

Keyboard

Telex

H1640

Maritime Computer

Connection

H4396

Box

Local Net

Matrix Printer

H1252

Control

Unit

SC4350

ABOVE DECK

BELOW DECK

SC4345

Control Handset

SAT-B Antenna

SA4415

Fascimile (G3)

Veritas

H4394/95

Connection Box

SAT-B Transceiver

ST4425C

can be replaced by Control Unit

All Control Handsets SC4345

SC4350 and vice versa.

Optional

Converter

Hard DiskOn / Off

1 INTRODUCTION Inmarsat B

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1.2 TECHNICAL DATA

Designation: SAT-B Ship Earth Station (SES) maritime class 1 with area group call capability and

normal tuning range, designed according to Inmarsat B System Definition Manual and

GMDSS requirements.

Configuration: SAT-B antenna SA4415

SAT-B transceiver, 24V ST4425 B/C

Control handset SC4345

Control unit, desk/bulkhead SC4350

Distress key SP4360

Interconnection: SAT-B antenna (ADE) to SAT-B transceiver (BDE):

Single coaxial cable (RG 214) up to 100 m carrying Rx/Tx IF signals (21.4/62.9 MHz),

data (4.8 kbit/s half duplex), 40.32 MHz reference signal and ADE power (40V DC).

SAT-B transceiver (BDE) to control handset and/or control units:

Multiconductor cable (8*0.25 mm

2

+ screen) up to 300 m implementing Scanbus

interface (LAN 76.8 kbit/s, ISOOSI 1-4), audio (Rx/Tx audio signal, 0 dBm) and power

(24V DC).

Services: Telephony incl. echo cancellation and DTMF signalling (APC vocoder, 16 kbit/s).

Telex (ITA-2, 50 baud).

Data communication (Hayes compatible (AT), 9.6 kbit/s).

Facsimile (CCITT group 3, 9.6 kbit/s).

Optional:

High speed data communication (56/64 kbit/s),

All modes available as duplex and fixed-originated simplex.

External I/F: Scanbus:

(DB-9 connector) Connection of control unit.

NMEA:

(DB-9 connector) Connection of 2-wire NMEA to GPS and GYRO.

DATA: (DB-9 connector) Connection of personal computer.

1 asynchronous serial (high speed) DTE/DCE port (9.6, 56, 64 kbit/s)

according to CCITT Rec. V.11 and X.27.

PC/Printer: (DB-15 connector) Connection of personal computer and printer.

1 asynchronous serial DTE/DCE port (50 baud telex and 9.6 kbit/s data)

according to CCITT Rec.V.24.

1 asynchronous serial DTE/DCE port (printer) according to CCITT Rec.

V24.

Alarm: (DB-15 connector) Connection of alarm unit and alarm indicating unit.

Phone1: (RJ-11 connector) 2W phone/PABX/FAX interface.

Phone2: (RJ-11 connector) 2W phone/PABX/FAX interface.

Antenna: Parabolic dish antenna for RHCP signals (21 dBi gain) with active stabilisation on 3

axes (azimuth, elevation and cross elevation) using rate sensors, inclinometers, and

signal strength tracking.

Transmission: 1626.5 - 1646.5 MHz (normal maritime tuning range, 20 kHz channel spacing for voice

communication).

EIRP = 25, 29, 33 dBW.

Reception: 1525 - 1545 MHz (normal maritime tuning range, 20 kHz channel spacing for voice

communication).

G/T = -4 dB/K.

Modulation: TX 24,132 kbit/s O-QPSK

RX 6 kbit/s BPSK, 24/132 kbit/s O-QPSK.

Coding: FEC convolution coding and 8 level soft decision Viterbi decoding (k = 7) and

(R = 1/2 , 3/4).

For high speed data, a sequential decoder with k = 36 and R = 1/2 is used.

Power Supply: Supply voltage: 24V DC +30/-10%.

Power consumption: TX/RX =250/120W

Environments: SAT-B antenna:

Temperature range: -25 to +55 °C.

SAT-B transceiver:

Temperature range: -15 to +55 °C.

Roll, pitch and yaw: ± 30° (T = 8 s), ± 10° (T = 6 s), ± 8° (T = 50 s)

Turning rate: ± 6 deg/s

Size and weight: SAT-B antenna:

H*W = 1410 mm * 1250 mm

M = 129 kg.

SAT-B transceiver:

H*W*D = 132 mm * 370 mm * 267 mm

M = 8.7 kg

Control handset:

H*L*B = 67 mm * 219 mm ‘ 70 mm

M = 1.2 kg

Control unit:

H*B*D = 100 mm * 200 mm * 120 mm

M = 0.8 kg

CONTENTS

2 SYSTEM DESCRIPTION 2-1

2.1 ABOVE DECK EQUIPMENT 2-1

2.1.1 PRINCIPLE OF STABILISATION 2-2

2.1.2 COMPONENTS OF THE STABILISATION SYSTEM 2-3

2.1.3 ANTENNA BEHAVIOUR DURING START-UP SEQUENCE 2-4

2.1.4 ANTENNA BEHAVIOUR DURING GLOBAL SEARCH 2-4

2.1.5 ANTENNA BEHAVIOUR DURING REGION SHIFT SEARCH 2-4

2.1.6 TRACKING ALGORITHM 2-5

2.1.7 COMMUNICATION, SETUP AND STATUS SURVEILLANCE 2-5

2.2 BELOW DECK EQUIPMENT 2-6

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9901

2 SYSTEM DESCRIPTION

The two main parts making up a terminal are described in this chapter. The description of the antenna unit

(ADE) consists of two parts, one concerning the RF and one about the stabilisation. The other main part

of the terminal is the transceiver unit.

2.1 ABOVE DECK EQUIPMENT

The block diagram shown in fig. 2.1 concerns the RF part of the antenna unit.

35522A

Synthesizer

Tracking

Receiver

Converter

Down

Synthesizer

LNA

HPA

Diplexer

Converter

Up

Triplexer Conn. Board

SMPS

Rotary Joint

TSP

Sensor

Block

Motors

DMB

Transmitter Level

Power Control Voltage

Serial Comm. to SMPS

Signal Strength

Data RX/TX

Filter selc.

Frequency Selc.

21.4 MHz RX

10.08 MHz ref.

62.9 MHz TX

DMB

To Transceiver Unit

Fig. 2.1.

The RF part consists of a transmitter and a receiver part sharing a single antenna. The diplexer separates

transmitter and receiver signals to allow full duplex transmission without transmitter degrading receiver

performance.

The transmitter part consists of an UP converter which mixes a fixed intermediate frequency signal to a

signal in the transmitter band (1.6265 - 1.6465 GHz). The frequency selection is made by means of the UP

converter synthesizer. In the HPA (high power amplifier) the low level signal from the UP converter is

amplified before it enters the diplexer and antenna.

The receiver part consists of an LNA (low noise amplifier) and two receiver units, a DOWN converter which

is the counter part of the UP converter, and a tracking receiver which is a part of the tracking and stabilisation

system. The output signal from LNA is split out to both units. The DOWN converter and DOWN converter

synthesizer mix the receiver band (1.525-1.545 GHz) to a fixed intermediate frequency of 21.4 MHz. Due

to different service types, voice, high speed data etc., different receiver bandwidths are required. In the

DOWN converter three bandwidths can be selected on the final intermediate frequency.

The tracking receiver is always tuned to the NCSC channel in a given ocean region. The reason this channel

type is used, is that there is always a signal presented from the satellite, unlike other channel types where

service activation is used. The tracking receiver can be thought of as a frequency selective power meter

which measures the signal level on the channel which it is tuned to. It has its own synthesizer and covers

the entire receiver band. The tracking receiver output is a direct voltage which is used as input for the

tracking and stabilisation system.

As described in the previous chapter, a single coax cable between transceiver unit and antenna unit is used.

To make this concept work, a triplexer is used to distribute the signals from the transceiver unit to the

different modules in the antenna unit and to combine the different signals from the antenna unit to a

composite signal before it enters the cable.

To make the transceiver unit and antenna unit work together, data communication between them is

necessary. On the triplexer board a data receiver/transmitter is placed. The kind of data exchanged between

2 SYSTEM DESCRIPTION Inmarsat B

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antenna unit and transceiver unit is status and fail information from the antenna and configuration data.

Configuration data concerns frequency set-up of the synthesizer, DOWN converter filter selection, and

transmitter power level. The received data from the transceiver unit is processed by a microcontroller placed

on the tracking and stabilisation processor board, which also takes care of data in the opposite direction.

The tracking and stabilisation processor board is the heart of the antenna stabilisation system. To stabilise

the platform, tilt sensor and rata sensors are placed in different places on the platform. Those sensors

together with the tracking receiver supply input to the tracking and stabilisation processor board, which, as

output, controls the motors. In the following chapter the stabilisation system is described in detail.

The connection from the triplexer to the coax cable is made by means of a connection board and a rotary

joint. The rotary joint is used instead of a cable unwrap system. On the connection board, the main 40V

supply voltage from the transceiver unit is taken out and connected to the input of the switch mode power

supply (SMPS). The SMPS delivers different kinds of supply voltages to the modules. Besides those fixed

voltages, a microprocessor controlled voltage used to regulate the output power from the HPA is also

delivered.

If for some reason signals between transceiver unit and antenna unit are missing, a signal called

dead man’s

button

is activated, shutting the regulated voltage to the HPA, thus preventing the HPA from transmitting.

2.1.1 PRINCIPLE OF STABILISATION

The main objective of the stabilisation system is to keep the antenna pointing as accurately as possible

in the referenced pointing direction at any time under environmental conditions (ship yaw, pitch and roll).

To obtain this the antenna stabilisation system is based on three axis active stabilisation with closed loop

control of each axis. The individual axes are named azimuth (yaw/turning correction), cross elevation and

elevation (roll and pitch correction) as shown in fig. 2.1.1. Each axis uses a double sensor principal for

angular movement measurement (combined measurement of angular rate and absolute angle) and an

electrical motor as actuator. The angular rate is measured by means of angular rate gyros based on

oscillating piezoelectric crystals. For absolute angle reference the elevation (El) and cross elevation (Ce)

axes use a fluid based inclinometer, and the azimuth (Az) axis uses the ships gyro compass.

35972B

Az

Ce

El

Fig. 2.1.1.

2 SYSTEM DESCRIPTION Inmarsat B

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The controller function of the stabilisation system is performed by the tracking and stabilisation processor

board (TSP board).

In addition to the three axes contributing to the active stabilisation (Az, El and Ce) the antenna is equipped

with a horizontal axis holding a small sensor box. The sensor box holds several of the sensors for the

stabilisation system. Its main function is to make it possible to keep the working point of the inclinometer

sensor as close to the real horizontal level as possible under all antenna elevation reference angles. When

the elevation part of the pointing reference changes, the angle between the antenna disc and the horizontal

box will be changed into the same angle value in the opposite direction, thus keeping the sensor box

horizontal at all times.

2.1.2 COMPONENTS OF THE STABILISATION SYSTEM

Fig. 2.1.2 shows a block diagram of the stabilisation system.

Az rate sensor

El rate sensor

Inclinometer

Tracking receiver

Ce rate censor

Motor Driver

Zero-mark det.

Horizontal

step motor

El axis

step motor

Az axis

step motor

Horizontal axis

DC motor

Brushless

TSP Controller

35973B

Fig. 2.1.2.

The stabilisation system can be divided into functional groups:

Azimuth axis:

Azimuth angular rate gyro sensor.

Fluxgate compass.

Ship gyro.

Azimuth step motor driver.

Azimuth step motor.

Elevation axis:

Elevation angular rate gyro sensor.

Elevation inclinometer (one axis of the dual axis inclinometer unit).

Elevation step motor driver.

Elevation step motor.

Cross elevation:

Cross elevation angular rate gyro sensor.

Cross elevation inclinometer (second axis of the dual axis inclinometer unit)

Cross elevation bldc motor driver.

Cross elevation bldc motor.

Horizontal axis:

Horizontal axis zero mark detector (optical fork).

Horizontal axis step motor driver.

Horizontal axis step motor.

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2.1.3 ANTENNA BEHAVIOUR DURING START-UP SEQUENCE

When the complete system, or just the ADE, has been reset or switched off and on, the ADE will initialize

and search for the satellite. The behaviour of the antenna during this process is described in this chapter.

1. Initialization

A few seconds after resetting, the horizontal axis will go to the bottom stop position. A knocking

sound will be heard for a few seconds. After this the axis will go up to the optical zero sensor.

Then the elevation axis will initialize in the same manner. Also from this axis a knocking sound

will be heard when it is in the bottom position. When the elevation axis has returned to horizontal

position, the cross-elevation axis will begin to move towards horizontal position. A high-fre-

quency switch-mode sound can be heard when the cross-elevation axis moves. The antenna will

be ready after 2-3 minutes.

If the transceiver has received the position of the vessel, the fast search will begin.

2. Fast search

The elevation axis will move up to the calculated elevation angle of the chosen satellite, and the

azimuth will turn clockwise 360°. This rotation will last about 1-2 minutes. After the search, the

azimuth will go to the position with the highest signal level. This rotation will last less than 1

minute. Here a fine search will be performed.

3. Fine search

The fine search is a cross-shaped search, the centre of which will be in the expected direction of

the satellite. The angular speed of this search is lower than the speed of the fast search. First

the elevation axis will search vertically from 20° below the expected satellite position to 20°

above this position. Then it will search horizontally from 15° to the left of the expected position

to 15° to the right of it. Finally it will move back to the azimuth and elevation angles where the

highest signal levels were measured. The fine search will last 1-2 minutes.

The total start-up sequence will last 5-6 minutes.

2.1.4 ANTENNA BEHAVIOUR DURING GLOBAL SEARCH

If the modem cannot achieve synchronisation on the received NCSC signal within 5 seconds after the fast

search, a global search will start. In this search mode the azimuth will rotate slowly 360° clockwise, and

at the same time the elevation axis will move up and down in a zigzag shape. The elevation top of this zigzag

is 80° above the horizon and the elevation bottom is 5° above the horizon. After this the satellite dish is

turned to the direction where the highest signal level was measured. A ± 25° horizontal and vertical fine

search is performed around the direction whre the highest signal level was measured.

The total global search will last between 6-7 minutes.

2.1.5 ANTENNA BEHAVIOUR DURING REGION SHIFT SEARCH

The behaviour of the antenna during a region shift search depends on whether the position of the vessel

is keyed in manually or received directly from a GPS. In the following description, the values in square

brackets are those of a position keyed in manually, the other values are with a functional GPS connected

to the system.

If for some reason the signal between the satellite system and the ship is blocked by eg. a smokestack

or an other object on board or ashore, it can be necessary to change to an other region. Blocking objects

can cause the signal level to drop to a value where the system is still receiving from the satellite, but where

the quality of the signal is too poor to perform communication. This error may occur if for instance several

calls (Ship to shore) fail, or if only two LEDs are illuminated on the handset. In such cases the transceiver

can be shifted to an other region, in which case a region shift search is performed.

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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 infor-

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.

2 SYSTEM DESCRIPTION Inmarsat B

2.2 BELOW DECK EQUIPMENT

The below deck equipment or transceiver unit as it is called consists of five printed circuit boards (modules)

as shown in fig. 2.3.

Pax

CSP/VDP

Modem

SPS

Rear Panel Connectors

SMI

SMPS

35974

Fig. 2.3.

SPS board

The SPS (signal path and synthesizer) board is the interface between the analogue RF parts at the antenna

unit and the digital signal processing in the transceiver unit. The receiver IF of 21.4 MHz is converted to

baseband, sampled and processed in a digital signal processor.

The transmitter part consists of a quadrature mixer where two baseband data signals are up converted and

combined to a 62.9 MHz IF signal. The baseband signals are generated in the modem module.

A data receiver and transmitter for communication with the antenna unit is also placed at this board.

All critical frequencies are derived from the system reference oscillator. The oscillator is a crystal oscillator

built into an oven.

The RF input/output to/from the SPS board is a single coax connection. Therefore, a combiner/splitter

circuit is used to combine the RF signals to be sent to the antenna unit and the split-out received RF signal

to the respective blocks which are to use them.

Modem board

The purpose of the modem board is to code data flow sent from the terminal to the satellite and decode data

flow received from the satellite. Coding is used to make it possible to detect and correct bit errors, thus

increasing the quality of the communication.

To increase the security, data bits are scrambled. Scrambling and descrambling takes place in the modem.

Data flow is transmitted/received in frames. The contents of a frame, besides the data to be transmitted

or received, are bit sequences helping the modem to synchronise. The modem takes care of the frame

format in both the receiver and the transmitter directions.

CSP/VDP board

The CSP/VDP board consists of two functionally separate parts. The CSP (control and signalling processor)

is the main processor in the system and takes care of the satellite protocol, man/machine and external

equipment interfaces.

The VDP (voice and data processor) is a digital signal processor which handles voice coding and decoding

and is the interface between modem and the PAX module for data and fax services.

PAGE 2-6

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2 SYSTEM DESCRIPTION Inmarsat B

PAGE 2-7

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PAX board

The PAX board (phone and fax) contains hardware and software for interfacing with a fax machine and with

push button telephones like a stand-alone telephone or a PABX network.

The module also acts as an interface for data communication from a single terminal or a local network at

transmission rates of 9.6 or 64 kbit/s (64 kbit/s only possible if high speed data is implemented).

SMI board

The SMI (switch mode power supply and interconnection) board contains the system power supply. From

the ship, the main supply voltage of 24V DC is connected at the rear panel of the transceiver unit. And from

that, the switch mode power supply generates a number of different voltages not only for the modules in

the transceiver unit but also 40V DC for the antenna unit.

At the rear panel of the transceiver unit, a number of connectors are placed for externally connected

equipment. Those connectors are mounted on the board, from where they are connected to the respective

modules by means of ribbon cables.

CONTENTS

3 MODULE DESCRIPTION 3-1

3.1 ABOVE DECK EQUIPMENT 3-1

3.1.1 ANTENNA 3-1

3.1.2 DIPLEXER 3-2

3.1.3 LNA 3-2

3.1.4 DOWN CONVERTER 3-3

3.1.5 UP CONVERTER 3-4

3.1.6 HPA 3-4

3.1.7 TRACKING RECEIVER 3-5

3.1.8 TRIPLEXER 3-6

3.1.9 SYNTHESIZER FOR TRACKING RECEIVER 3-8

3.1.10 SYNTHESIZER FOR UP/DOWN CONVERTER 3-10

3.1.11 SWITCH MODE POWER SUPPLY 3-13

3.1.12 TSP 3-14

3.1.13 TILT SENSOR 3-15

3.2 BELOW DECK EQUIPMENT 3-16

3.2.1 SPS BOARD 3-16

3.2.2 MODEM BOARD 3-18

3.2.3 CSP/VDP BOARD 3-19

3.2.4 PAX BOARD 3-20

3.2.5 SMI BOARD 3-21

3.2.6 HANDSET 3-22

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Inmarsat B

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