Comtech EF Data CSAT-6070 - Manual (Page 109)

Appendix D. THEORY OF OPERATION
D.1 RF Signal Conversion ...................... D–2
D.1.1 Downconverter .............................. D–2
D.1.2 Upconverter................................... D–3
D.2 Monitor & Control ............................. D–4
This appendix contains a general description of the theory of operation for the CSAT
downconveter and upconverter sections. The CSAT can be used for SCPC, DAMA AND
TDMA, as well as for full transponder HDTV and analog TV, applications.
The description in this appendix is for the standard 25Watt transceiver. For other
models, refer to Chapter 1. Introduction, for the correct frequency, gain, and output
power levels associated with it. In all models, the downconverter and upconverter
local oscillators are independently synthesized to allow simplex or duplex operation.
In order to minimize complexity, they share a common power supply, an internal
high stability 10 MHz reference oscillator, and the Maintenance and Control
(M&C) unit.
The downconverter section operates in the frequency range of 4500 to 4800 MHz, with a
temperature compensated gain of 45 dB. This high level of gain provides an IF output signal
level of +13 dBm at 1 dB of gain compression. This provides the capability to handle longer
modem cable runs, or fan out for splitting networks without requiring additional line amplifiers.
The upconverter section operates over a frequency range of 6725 to 7025 MHz with a
temperature compensated gain of 71 dB. The RF output level is +44 dBm minimum at 1 dB gain
compression over the operating temperature range.
The phase noise performance of both the upconverter and downconverter sections exceeds the
Intelsat phase noise mask for IBS and IDR services by 6 dB. This allows phase dependent
demodulators to provide the best possible performance. The close-in phase noise is also very
low making the converter ideal for low data rate applications such as DAMA hub earth stations.
An auto select EIA-232 or EIA-485 pin out is available in the circular COM connector on the
exterior of the chassis. All configuration control, status retrieval and unit adjustments are
available as ASCII commands through this interface.
D–1