Rf Con/Cpu Board (16P0208A) - Nera Inmarsat-c Service Manual

2.3.1 RF CON/CPU board (16P0208A)

The following describes the function of RF CON/CPU board.
Analog part
- Dividing the received RF signal to [D-GPS] terminal for D-GPS decoder.
- Dividing the received RF signal to GPS receiving board (GN-79, option).
- Changing the received RF signal to the IF signal: 1.2 kHz.
- Generating the 400 kHz TX/RX frequencies at PLL synthesizer circuit. (TX: 1626.5 MHz
to 1646.5 MHz Rx: 1530.0 MHz to1545 MHz)
- BPSK modulating at DDS.
Fig.2.3.2 shows the synchronizing detection circuit.
CPU
- Controlling communication protocol of Inmarsat C.
- TX/RX signal processing
- TX/RX changing
- Controlling AGC, PLL and DDS circuit
- Communicating with TERM CPU
- Controlling the Distress Alert Received unit(IC-305) and the Alarm unit(IC-306)
- Handling IEC-61162 (NMEA) data
- Monitoring SYN, CHECK V (the supplied voltage for the antenna) and ANT C (Antenna
current)
Memory (see page 2-27)
- RAM: Backed up for 72 hours
- EEPROM: Memorizing FW/RT ID, ENID, DNID
Fig.2.3.2 Synchronizing detection circuit
2-7
2.3 Terminal unit, IC-215