Comtech EF Data CST-5000 - Manual (Page 122)

CST-5000 C-Band Satellite Terminal 140 MHz IF Option
Rev. 9 A–3
A.1.1.1 Specifications
Input 10.0 MHz square wave, CMOS levels
Output 1112.5 MHz (2 each)
Connectors SMA
Output Impedance
50 Ω
Output Level +7.0 dBm
A.1.2 Synthesizer
The 140 MHz IF terminal requires a single synthesizer with two outputs:
• One for the down converter to convert the RF input to 140 MHz output
• One for the up converter to convert 140 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.1.2.1 Specifications
RF Inputs
Connector type
Impedance
Input level
10 MHz CMOS square wave
SMA
50
Ω
+7 dBm
RF Outputs
Connector type
Impedance
Level
Frequencies 4592.5 to 5172.5 MHz
SMA
50
Ω
+7 dBm
A.1.2.2 Theory of Operation
The synthesizer module multiplies the 10 MHz reference clock to a variable clock by use
of a VCO, loop filter, phase detector, and a variable divide-down chain. The divide-down
chain is controlled by the M&C board through the use of three serial signals. A frequency
tripler 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.
Refer to Figure Appendix A-2 for a block diagram of the LO synthesizer.