Linksync, Automatic frequency control – Comtech EF Data MIDAS 4 System and Design User Manual
Page 49
System and Design Manual, Revision 2
Theory of Operation 3–7
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LinkSync™ is a unique MIDAS feature providing:
• Automatic Frequency Control (AFC)
• Uplink Power Control (UPC) at the MIDAS Controller
• Circuit Power Management (Option)
♦ Site level call blocking based on HPA power
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MIDAS provides automatic frequency control (AFC) to reduce the traffic
modem acquisition time for continuous mode operation and to improve the
burst acquisition performance of the SNM-1001 Network Control Modem and
the Node Control Modems
1
, by keeping the frequency drift to within
±
500 Hz.
The outbound control channel is used as the system-wide reference, which is
continuously monitored by the LinkSync™ Modem at the MIDAS Controller
site and all the Node Control Modems
2
. The AFC process does not depend on
the absolute accuracy in any part of the system.
The AFC process consists of three steps:
1. Removing the receive offset of the Network Control Modem at the
MIDAS Controller.
2. Removing the receive offset of the Node Control Modems and the traffic
modems at the traffic sites.
3. Removing the transmit offset of the Node Control Modems and the traffic
modems at the traffic sites.
1
Includes SNM-1000 and the integrated traffic/control modems (SNM-1010 and
SNM-1010L).
2
The integrated traffic/control modems and the network terminals in a standard
configuration monitor the outbound control channel in the “control mode”.