Comtech EF Data DT-4572 Installation And Operation Manual page 29

DT-4572 X-Band Down Converter MN/DT4572.IOM
Introduction Revision 1
The phase noise performance exceeds the Intelsat phase noise mask for IBS and
IDR services by more than 9 dB. This allows high capacity earth stations to add
more demodulators and still meet transmission standards. The close-in phase
noise is also very low. This makes the converter ideal for low bit rate digital
circuits such as used in DAMA hub earth stations.
Depending on the application, the converter chassis rear panel module slot
accepts an Input/Output Module (IOM), Polarity Switch Module (PSM), Transmit
Switch Module (TSM), Equalizer Module (EQM), or Receive Switch Module (RSM).
The converter RF, IF, and High-Speed Bus (HSB) connectors are integral to the
installed module.
An IOM can be installed for switching the RF output for single thread operations,
or for testing the output of the unit.
In redundancy applications, where converters are "Daisy Chained" to provide
distributed online protection switching to a backup converter (BU), a TSM is used
in place of an IOM. The TSM contains RF and IF transfer switches. Type 'N' female
connectors are provided for the RF loop, and 50 Ω or 75Ω BNC female connectors
are provided for the IF loop.
The "Daisy Chain" configuration is designed to chain the IF output of up to twelve
(12) online converters through RSMs terminating in a BU. When a fault occurs in
an online converter, the RSM in the faulted converter is commanded to switch to
the BU.
The BU in the "Daisy Chain" communicates with the online converters through
the installed module's High Speed Bus (HSB data interface). When faults are
detected, the BU reconfigures itself to replace the faulted online converter. The
BU also uses the HSB to monitor configuration changes made to the online
converters by either remote control or front panel command inputs.
The BU performs fault detection, self-reconfiguration, and logical switching
functions. If the BU has a fault, it is prevented from performing the protection-
switching task. If the BU does not have a fault, it assumes the frequency and
attenuation of the faulted online converter, and compensates for the chain
losses.
1–3