Rf Signal Conversion - Comtech EF Data UT-4518E-1 Installation And Operation Manual

UT4500 Series Up Converter
Theory of Operation
The "Daisy Chain" configuration is designed to chain the IF input and RF output of up to
twelve (12) on-line converters together through TSM's terminating in a backup converter.
When a fault occurs in an on-line converter, the TSM 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 UT-4500 Series Up Converters 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 100
watts. The converter can operated in a temperature environment of 0 to 50 degrees C 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, in the Model UT-4514 Up Converter,
the 70 MHz IF input is mixed in the first mixer with a 1150 MHz IFLO signal. The IFLO
is locked to a 5/10 MHz reference oscillator. The first mixer is located in the Signal Path
Assembly.
The intermediate IF is 1220 MHz which is mixed in the second stage mixer with 12780 to
13280 MHz synthesizer signal to provide an RF output frequency of 14000 to 1451X
MHz in 125 KHz fine tuning steps. The synthesizer is also locked to the 5/10 MHz
reference oscillator. The second mixer is located in the converter Signal Path Module,
and the synthesizer consists of the Coarse/Fine Step Module and Sum Loop Module.
Figure 33 is a typical functional block diagram of the converter.
C
ONVERSION
80
MN/UT4500.IOM
Rev. 0