Comtech EF Data CDM-Qx, Инструкция по установке и эксплуатации

Страница: 45 / 224

CDM-Qx Satellite Modem Revision 6
External Connections MN/CDMQx.IOM
4.4.9 TX and RX IF Connectors
The type of IF connectors available depends on the configuration ordered. The following
reflects configurations available:
The female BNC 50
Ω
reference connector, standard on all configurations, provides an
external reference input for the Tx and Rx IF synthesizers and for the internal transmit
clock. The load impedance is 60.4
Ω
, so the VSWR is less than 1.25:1 at either 50
Ω
or 75
Ω
.
Input level is 0 dBm minimum to +20 dBm maximum at either 1, 2, 5, 10, or 20 MHz.
When external reference is enabled, the internal 10 MHz reference oscillator is phase
locked to the external reference input by a 10Hz bandwidth PLL. If no activity is present at
the external reference input, the modem will revert to the internal 10 MHz reference.
70/140 MHz L-Band
•
Tx and Rx:
o
70/140 MHz – BNC 75
Ω
o
L-Band – N-Type 50
Ω
•
Reference: BNC 50
Ω
female
4.4.10 HSSI Interface
This data interface is a plug-in module that inserts into the rear of the CDM-Qx’s
Modulators or Demodulators. It provides physical and electrical connection between the
external terrestrial device and the internal circuitry of the modulator or demodulator. By
convention, a modem is
D ata C ommunications E quipment (DCE) where Tx data enters
the data interface and Rx data exits it. The plug-in interface has full duplex capability.
In addition, the module is automatically configured for simplex-transmit or simplex-
receive operation when the module is plugged into a Modulator and Demodulator. When
the CDM-Qx is configured as a modem, only the Demodulator is required to have a HSSI
Interface and the Modulator is assigned a blank panel with Alarm output only.
The HSSI Card Data Interface Module plugs into the rear of the Modulator or
Demodulator. Figure 4-3 shows a block diagram of the interface. The HSSI interface
provides:
♦
A single HSSI interface
♦
DCE Connection:
!
ST clock is sourced to the terrestrial interface for use as reference by DTE
!
TT is treated as an incoming External Clock, and the interface phase locks to it
!
TA / CA is supported
A summary of specifications for the interface is provided in Table 4-8 and the connector
pinout is shown in Table 4-9.
4–11