Principles of Satellite Communications, 4-4 - Lab-Volt

Exercise
4-4
Troubleshooting a Satellite Communication Link
EXERCISE OBJECTIVE
When you have completed this exercise, you will have used a systematic
technique to diagnose instructor-inserted faults in a satellite link formed by the
Earth Station Transmitter, the Satellite Repeater, and the Earth Station Receiver.
DISCUSSION
Troubleshooting a satellite communication link
A complete satellite communication link involves many different components.
Troubleshooting a satellite communication link therefore requires a thorough
understanding of each component and a familiarity with the normal signals at
each stage.
It is suggested that you review each of the preceding troubleshooting exercises
before troubleshooting an entire link.
PROCEDURE OUTLINE
The Procedure is divided into the following sections:
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ƒ
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PROCEDURE
System startup
Observing normal operation
Troubleshooting an unknown fault
System startup
1. If not already done, set up the system and align the antennas visually as
shown in Appendix B.
2. Make sure that no hardware faults have been activated in the Earth Station
Transmitter or the Earth Station Receiver.
b
Faults in these modules are activated for troubleshooting exercises using DIP
switches located behind a removable panel on the back of these modules. For
normal operation, all fault DIP switches should be in the “O” position.
3. Turn on each module that has a front panel Power switch (push the switch
into the I position). After a few seconds, the Power LED should light.
© Festo Didactic 86311-00
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Ex. 4-4 – Troubleshooting a Satellite Communication Link  Procedure
4. If you are using the optional Telemetry and Instrumentation Add-On:
x
Make sure there is a USB connection between the Data
Generation/Acquisition Interface, the Virtual Instrument, and the host
computer, as described in Appendix B.
x
Turn on the Virtual Instrument using the rear panel power switch.
b
x
If the TiePieSCOPE drivers need to be installed, this will be done
automatically in Windows 7 and 8. In Windows XP, the Found New
Hardware Wizard will appear (it may appear twice). In this case, do not
connect to Windows Update (select No, not this time and click Next). Then
select Install the software automatically and click Next.
Start the Telemetry and Instrumentation application. In the Application
Selector, do not select Work in stand-alone mode.
b
If the Telemetry and Instrumentation application is already running, exit
and restart it. This will ensure that no faults are active in the Satellite
Repeater.
Observing normal operation
5. Make the connections shown in Figure 4-5.
Binary Sequence
Generator
(BSG) 1
Binary Sequence
Generator
(BSG) 2
Binary Sequence
Generator
(BSG) 3
BIT
CLOCK
DATA
DATA
INPUT 1
RF
OUTPUT
DATA
IF 1
OUTPUT
DATA
INPUT 2
Digital
Modulator
DATA
DATA
INPUT 3
Up Converter
1
Up Converter
2
Earth Station Transmitter
BIT CLOCK OUTPUT
I Q
I Q
Satellite
Repeater
RF OUTPUT
Earth Station Receiver
Down Converter
2
Down Converter
1
Digital
Demodulator
I Q
I Q
IF 2
OUTPUT
Figure 4-5. Connections for transmission and reception of TDM data.
a
294
There are no faults in the Analog Modulator and Analog Demodulator sections
of the modules.
© Festo Didactic 86311-00
Ex. 4-4 – Troubleshooting a Satellite Communication Link  Conclusion
6. Using the appropriate instruments, review the normal operation and signals
in all of the modules. Print or sketch the instrument screens that you think will
be useful for reference.
Consult your answers to procedure step questions and notes taken during
the exercises.
Troubleshooting an unknown fault
7. Ask your instructor to activate a fault in one of the modules of the Satellite
Communications Training System.
a
Faults can only be activated in the Satellite Repeater by telemetry using the
Telemetry and Instrumentation Add-On.
8. Carry out the troubleshooting procedure in order to locate the fault and
diagnose the problem. Use analog or digital transmission as necessary to
locate the fault. Write your results on a Troubleshooting Worksheet provided
at the end of this exercise.
9. If desired, ask your instructor to activate another fault. Troubleshoot the new
fault using another Troubleshooting Worksheet.
10. When you have finished using the system, exit any software being used and
turn off the equipment.
CONCLUSION
© Festo Didactic 86311-00
In this exercise, you used your troubleshooting skills to locate and diagnose a
fault in a complete satellite communication link. You observed that many different
techniques are required to verify system operation and troubleshoot the fault.
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Ex. 4-4 – Troubleshooting a Satellite Communication Link  Troubleshooting Worksheet
TROUBLESHOOTING WORKSHEET
Student’s Name:
_______________________________________________________________
Instructor’s Name:
_______________________________________________________________
Fault:*
_______________________________________________________________
Troubleshooting Procedure:
1.
Identify the defective module(s) or mode(s) and check visually for damage.
2.
Verify that power supplied to all modules. Note all status LEDs and other indicators.
3.
Apply the appropriate signals and use signal flow tracing to locate the problem.
4.
Verify any other input branch, if present.
5.
Make sure the malfunction located plausibly explains the problem observed.
6.
Diagnose the problem.
Problem Description and Symptoms: ________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
Defective circuit: ________________________________________________________________________
_____________________________________________________________________________________
Diagnosis: _____________________________________________________________________________
_____________________________________________________________________________________
Instructor’s Comments: ___________________________________________________________________
_____________________________________________________________________________________
Notes: ________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
* At instructor’s discretion
296
© Festo Didactic 86311-00
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