Comtech EF Data HPCST-5000 - Manual (Page 140)

Theory of Operation High-Power C-Band Satellite Terminal
6–14 Rev. 0
6.4 Synthesizer
The RFT-500 uses two synthesizers (optional single synthesizer):
! One for the down converter to convert the RF input to a 70 MHz IF output
! One for the up converter to convert the 70 MHz input to the RF output
The purpose of the synthesizer module is to convert the 10 MHz reference signal to a
variable frequency to perform the conversion. A single synthesizer option is available.
When the up converter is programmed, the down converter frequency is automatically
selected.
6.4.1 Specifications
Refer to Table 6-8 for specifications.
Table 6-8. Synthesizer Specifications
Parameter Specification
RF Inputs:
Connector type
Impedance
Input level
10 MHz CMOS square wave
2120 MHz reference (from IFLO)
SMA
50
$
+7 dBm
RF Outputs:
Connector type
Impedance
Level
U/C frequencies 4715 to 5295 MHz
D/C frequencies 4610 to 5190 MHz
Single 4662.5 to 5242.5 MHz
SMA
50
$
+7 dBm
6.4.2 Theory of Operation
The synthesizer module multiplies the 10 MHz reference clock to a variable clock by use
of:
! VCOs
! Loop filters
! Phase detectors
! Variable divide-down chain
The divide-down chain is controlled by the M&C board through the use of 14 parallel
CMOS signals. The down converter divide-down chain varies from 150 to 380. The up
converter divide-down chain varies from 222 to 422. A frequency doubler is then applied
to produce the final output.
The VCO tuning voltage is sent to the M&C for monitoring, as well as a lock detect
fault.