Rf Signal Conversion - Comtech EF Data DT-4572 Installation And Operation Manual

DT4572 X-Band Down Converter
Theory of Operation
The "Daisy Chain" configuration is designed to chain the IF output of up to 12 on-line
converters together through RSM's terminating in a backup Converter. When a fault
occurs in an on-line converter, the RSM in the converter with the fault is commanded to
switch to the backup Converter. The backup Converter performs the fault detection, self
reconfiguration and the logical switching functions. If the backup Converter has a fault,
it will not attempt to perform the protection switching task. If the backup Converter does
not have a fault, it will assume the frequency and attenuation of the faulted on-line
converter, and compensate for the chain losses.
The backup Converter in the "Daisy Chain" communicates with the on-line converters
through a high speed (data interface) bus (HSB). When faults are detected the backup
Converter re-configures itself to replace the on-line converter with the fault. The backup
Converter also uses the HSB to monitor configuration changes made to the on-line
converters by either remote control or front panel command inputs. Changes in
frequency, attenuation or polarity are entered into the backup table as they are made, as
well as information from new on-line units. The HSB does not interfere with the remote
control communications link for access to any of the converters in the "Daisy Chain".
The DT-4572 Down Converter are a standard 19-inch rack mounted units, 1.75 inches in
height. The converter is 22 inches deep, and weighs 25 pounds. Prime power the
converter can be either 100 to 125 VAC, or 205 to 240 VAC, at 47 to 63 Hz (or provided
with an optional -48 VDC prime power input). The power dissipation is 60 watts. The
converter can operated in a temperature environment of 0 to 50°C (32 to 122°F) at 10,000
feet altitude in 0 to 95% relative humidity.
C.2 RF S
IGNAL
As a typical example of the RF signal processing, the RF input to the DT-4572 Down
Converter is 7250 to 7750 MHz at a typical level of -45 dBm. The RF is mixed in the
first mixer with a 6030 to 6530 MHz synthesizer signal from a multiplier, in 125 kHz fine
tuning steps. The synthesizer is locked to a 5/10 MHz reference oscillator. The first
mixer is located in the converter Signal Path Module, and the synthesizer consists of a
Coarse/Fine Step Module and a Sum Loop Module.
The intermediate IF is 1230 MHz which is mixed in the second mixer with the 1290 MHz
IFLO providing a +20 dBm, at 1 dB compression, 70 MHz IF output. The second mixer
is also located in the converter Signal Path Assembly.
Figure 33 is a typical functional block diagram of the converter.
C
ONVERSION
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Rev. 0
MM/DT4572.IOM