COMMUNICATION SYSTEM

  • The system has two communication channels; the CW and the FM channels. The CW channel is used for sending the Beacon Morse code at 60 WPM, the beacon duration is about 10 Sec; while the FM channel uses AX.25 protocol to communicate with the ground control station. The communication subsystem uses SSP protocol on the satellite internal bus where it acts like a router that receives the ground commands and forward them to the required subsystem, then it receives the response and replies properly to the ground station through the FM channel, also the communication subsystem stores the captured image to be downloaded to the ground station upon request during the communication session.
  • Interface
  • The communication modules is connected to the main bus through 2 UART interfaces.
  • There is an SPI link between the communication modules and the Payload camera subsystem that is used in the image transmission.
  • Protocols
  • The communication modules communicates with the GCS using AX.25 Protocol.
  • There is an SPI link between the communication modules and the Payload camera subsystem that is used in the image transmission.
  • FM Channel
  • It is a half-duplex channel.
  • Used in communicating with the ground station.
  • The used data rate is 4800 b/s.
  • Transmitted RF Power 30 dBm.
  • CW Channel
  • It is a TX channel.
  • Transmitted RF Power 30 dBm.
  • Used in sending the beacon signal.
  • The used data rate is 60 w/m.
  • Transmitted RF Power 28.5 dBm.
  • Morse Code is used as the encoder.
  • The module has MSP430 microcontroller with SPI FLASH - NOR Memory I64Mb; and temperature sensor for power amplifier.
  • The antenna used is a deployable V-shaped antenna with the following parameters:
  • Working frequency: 437 MHz
  • VSWR=1.7
  • Gain=0 dB
  • Pattern= Near omnidirectional

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