User's Manual Part 1

3EM21522AAAA Functiona
l
Description
Issue 1, March 2008 DTR-0200-SA-SIRIUS
2-5
2.3 MAIN FUNCTIONS
The Sirius Terrestrial Repeater consists of the following main functions:
•
Receiver – Receives the down converted input signal from the VSAT Antenna/
LBN via coax cable. Processes the received signal for transmission to the modula-
tor.
•
Transmitter – (modulator, up converter, HPA, bandpass filter, and output
coupler) Transmits the received and processed RF signal, via tower mounted
antenna,
to the end user’s equipment.
•
Timing – A GPS receiver provides signals for synchronization within the Signal
Processing Unit (SPU).
•
Monitor and Control – This function is primarily performed by the main con-
troller board which receives information from all external devices, including
temperature, power to antenna, output signal control parameters, and equipment
condition.
•
Power Distribution – Power is controlled and distributed by a power distribu-
tion unit (PDU) and a relay control group.
Functional description of the components involved in these main functions follows.
2.3.1 SIGNAL PROCESSING UNIT (SPU) SUB-ASSEMBLY
Figure 2 - 2 and Figure 2 - 3 respectively show a physical representation and functional
block diagram of the SPU.
The primary function of the SPU is to receive the complex digital data stream
(CDDS) from the
VSAT satellite, modulate the received signal into a COFDM wave-
form, up-convert the waveform to the assigned S-Band frequency within the user’s
frequency plan,
and forward this waveform to the HPA in the transmitter portion of
the repeater.
The SPU contains the L-Band satellite receiver, modulator, up-converter, main con-
troller, and Uninterruptible Power Supply (UPS).