AS 680/682
Subsystem Description Description, Operation and Maintenance
ADS−B
2−4 Ed. 10.07
2.1.4 Signal Processing Unit (SPU)
See Figs. 2−2 to 2−7.
As the Ground Station equipment is intended to be installed in remote sites with power and space
constraints, considerable importance was attached to finding a solution that combines the utmost
performance at lowest possible power consumption and size. The SPU design led to a robust and
compact Ground Station drawer with small dimensions of only 3 height units (HU) in standard 19"
format, ready for integration into existing racks. If there is no space available at a certain site, a small
cabinet can be easily provided off the shelf.
The power consumption is approx. 55 VA. As standard, the SPU is equipped with a DC/DC converter
which is to be supplied with nominal +24 VDC (18 to 36 VDC). As option for connecting to mains sup-
ply, an AC/DC converter is available which is to be supplied with nominal 230 VAC (100 to 240 VAC,
50/60 Hz). The electronic subassemblies are cooled with a built in, removable fan unit, located at the
inner right side. The SPU is built by the following main subassemblies:
− Receiver unit for ADS−B signals (RXU)
− GPS Timing System (GTS), GPS Receiver for GPS SIS signals
− Signal Processing Board (SPB)
− Single Board Computer (SBC)
− Power Supply, DC/DC or AC/DC (option)
− Fan unit
All user relevant connectors and indicators are located on the SPU front. The front is equipped with
handles to facilitate the insertion and removal of the subrack. The power connectors including fuses
and filters (AC and DC) and the mains switch (with AC/DC option) are located at the rear of the SPU.
NOTE: The label containing part and serial number of the entire SPU as well as the label describ-
ing its power consumption is located on the subrack’s backpanel. The label on the side
is indicating the part and serial number of the chassis itself. Refer to Fig. 2−5.
Power Supply (DC/DC)
DC on switch
Air Inlet GPS RX GTS DG14
SBC SPB Fan unit
RXU
Air outlet
Fig. 2−3 SPU 19" subrack, front view
DC input connector with fuse holder (2x 6.3 AT)Air outlet
DC inputFuses AC inputFuses Mains switchPE PEPE=Protective Earth
Option: mains input connector with AC switch and fuse holder (2x 0.8 AT)
Input voltage 18−36 VDC
Current in 4.5 A max.
Fuses 2x 6.3 AT/250 V
1/4" x 1.1/4"
Input voltage 100−240 VAC
Current in 0.5 A max.
Fuses 2x 0.8 AT/250 V
1/4" x 1.1/4"
Fig. 2−4 SPU 19" subrack, rear view, DC/DC and AC/DC option
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