Figure D-1 Functional Block Diagram Of The Downconverter Section - Comtech EF Data CSAT-5060 Installation And Operation Manual

100W C-Band Transceiver
Theory of Operation
D.1 RF S
IGNAL
D.1.1 D
OWNCONVERTER
The RF input to the downconverter is in the 3400 to 4200 MHz frequency range
at a typical level of -45 dBm. The input signal is mixed down to the 1110 MHz
IF in the first conversion mixer. High side LO injection is used for this mixing
process. It is provided by the downconverter RFLO synthesizer in the 4510 to
5310 MHz frequency range in 1.000 or 2.500 MHz steps. Both step sizes are
automatically selectable.
IF filtering is provided by the 1110 MHz BPF. It is just wide enough to pass the
36 MHz bandwidth of the desired signal while maintaining more than adequate
amplitude and group delay flatness. At the same time, it is narrow enough to
provide the necessary rejection to the image, the RFLO, and other spurious
signals. The second mixer operates at a fixed input frequency of 1110 MHz. It
operates with high side LO injection at 1180 MHz provided by the
downconverter IFLO and converts the IF signal down to the 70 ±18 MHz output
frequency.
3 4 00 -
4 2 00 M Hz
3 40 0 - 42 0 0 M Hz
CO M M & C
REFERENCE

Figure D-1 Functional block diagram of the downconverter section

C
ONVERSION
V A R
A TTEN
RFLO
10 M Hz
45 1 0 -
5 3 10 M Hz
1 1 1 0 M Hz BP F
1 1 8 0 M Hz
D-2
Revision 0
MN/CSAT5060100.IOM
V A R
A TTEN
IFLO
P O WER
1 18 0 M Hz SUP P LY
7 0 +/ - 1 8 M Hz