AS 680/682
Subsystem Description Description, Operation and Maintenance
ADS−B
2−8 Ed. 10.07
2.1.4.3 Signal Processing Board (SPB)
See Fig. 2−10.
The Signal Processing Board is used to process the video signal of the RXU. The implemented algo-
rithms in the SPB (e.g. 25% of the 1st preamble pulse amplitude) are applied on the video input signal
only and do not consider the receiver characteristics. In detail the following processes are executed
by the SPB:
− Video signal processing
− Preamble detection
− Message decoding
− Retriggering, if a weaker Mode−S is overlapped by a stronger Mode−S message, the weaker
message will be disturbed, therefore the stronger message is decoded.
The following table gives a definition of the indicators and controls of the SPB module.
Board Indicator Color Control Function of control or indicator (lit or flashing)
SPB
LED, Fail
LED, RxDL
LED, TxUL
LED, TxDL
LED, TSC
LED, OVF
LED, TxN
LED, RxN
LED, TxH
LED, RxH
LED, Bite
LED, Main
red
green
green
green
green
green
green
green
green
green
green
green
Reset Recessed key, manual reset of SPB.
Normally out; BITE indication if watchdog fails.
Flashing, indicates receiving a valid MODE−S
telegram (preamble).
Normally out, indicates the transmission of an
uplink message (only valid with uplink
modulator option).
Normally out, indicates the transmission of a
downlink message (only valid with downlink
modulator option).
Flashing, indicates SNMP activity on the
network.
If lit, indicates an overflow in the input hard-
ware buffer of the SPB.
If lit, indicates that a data packet has been
written to the network.
If lit, indicates that a data packet has been
read from the network.
If lit, indicates that data has been sent to the
hardware (only valid with uplink or downlink
modulator option).
If lit, indicates that data has been read from
the hardware telegram buffer.
If lit, indicates that the BITE process is active.
If lit, indicates that the MAIN process is active.
front view
LED indications BITE I/OStatus interfaceBoard reset Serial RS232Trigger in
TX−Control out I/O
J5 J3 J4 J6
Exchange
Fig. 2−10 Signal Processing Board (SPB)
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