Comtech EF Data KST-12025 - Manual (Page 103)

KST-12025 Ku-Band Satellite Terminal Theory of Operation
Rev. 1 5–17
5.5.2 Theory of Operation
The RFT-1225 employs the down converter to convert a band of signals within the 10.95
to 12.75 GHz frequency range to a baseband 70 MHz output IF signal.
The frequency conversion utilizes a dual-conversion process:
•
The first conversion mixes the input RF signal with the synthesizer input to
down convert to the first IF 1220 MHz.
•
The second conversion mixes the first IF signal with the IFLO input to down
convert to the baseband IF of 70 MHz (
± 18 MHz).
The synthesizer input is generated externally by the down converter synthesizer. The
IFLO is also generated externally by the IFLO assembly.
The input power level of both the synthesizer and IFLO will be at a nominal +8 to
+10 dBm coming into the down converter.
The M&C board interpolates the factory preset compensation data that is stored in an
EEPROM inside the down converter. This data allows the M&C board to command and
compensate the down converter’s output power, ensuring proper output power levels
over the entire frequency and temperature range.
The M&C board also supplies the DC power for the LNA, which is subsequently
injected into the RF input connector.
5.6 Up Converter
The function of the up converter is to convert the 70 MHz IF signal used in the indoor
unit modem to a Ku-band signal to be sent to the high-power amplifier.
Refer to Figure 5-9 for a functional block diagram of the up converter.