User's Manual Part 1

3EM21522AAAA Functiona
l
Description
Issue 1, March 2008 DTR-0200-SA-SIRIUS
2-15
• RF Power: Monitoring is two channel and RS485 full duplex. The path is from the
reflected power and forward power detectors through DB9-M panel connector
P6B into the processors UART1 and UART2. The Atmega256 processor initial-
izes the GPS Receiver, makes all necessary settings and then monitors important
stats (refer to GPS Receiver below).
2.3.1.4.3 GPS Receiver
The GPS receiver provides 10 MHz and 1 pps signals for synchronization purposes.
The signals’ exact alignment to a UTC/GPS second is monitored via a message
received by the controller as a response to the correspondent’s request. The receiver
supports proprietary binary messages and also NMEA formatted message protocol.
A subset of the protocols is used by the MPC860 microprocessor to control receiver
operation. After initialization, the GPS starts tracking the satellites to determine its
position; the accuracy of the GPS output signals depends on the GPS satellite recep-
tion. The Controller communicates continuously with the GPS to deter-mine if the
GPS is still operating correctly and still receiving the satellite signals
, etc., or if it
has any alarm (malfunction) to report. The output of the GPS (1 pps and 10MHz
pulses) is to the Distribution Amplifiers, which in turn feed the pulses to the Modula-
tor and Up-converter via internal connector J130.
2.3.1.4.4 Dial-up Modem
Two chips, Si2457 and Si3018, make up an internal modem and provide the required
connectivity to POTS (PSTN). The phone line connection is via an RJ11connector
(J119 on the front panel). This telephone communication channel provides the main
control interface for repeater monitoring by the Sirius repeater NMS. Information
exchange between site and NMS is via SNMP.
2.3.1.4.5 Ethernet Switch
The Ethernet switch is a built-in 10/100 Base-T switch and provides four RJ-45
Ethernet ports allowing the controller to communicate with other Ethernet devices.
2.3.1.4.6 Uninterruptible Power Supply (UPS)
See Figure 2 - 9 . The UPS monitors the AC line status and if the AC voltage drops, it
provides +5V and +3.3V for CPU backup. The UPS provides CPU back-up power for
up to 5 minutes
, enough time to store the current state of the repeater, store param-
eters in volatile memory, notify NMS, and completely and safely shut down the
repeater
. The unit comprises a bank of five Ultra Capacitors, 350F/2.5V each, a DC/
DC converter, over-voltage protection and charging/discharging circuitry. During
repeater power-up, the capacitors charge through a current limiting resistor with
the bulk of the power going to the SPU and no interruption of power during this
period. When power is interrupted, the capacitors discharge to the load through the
DC/DC converter at a steady five volts until they reach approximately seven volts at
which time the SPU power is terminated.