Low Speed Serial Bus (LSSB)

Status date

Modern Telecom Satellites provide 45-60 transponders with Ku- and C-band frequencies.

Behind each channel is a TWTA (Travelling Wave Tube Amplifiers) or a MPM (Microwave Power Module) which is connected by an individual harness (cable of many parallel wires) to provide the power supply, send signals to switch MPM on/off or give gain step commands to the LCAMP (TC, Tele-Command) and get the unit status by telemetry (TM) signals.

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Telecommands and Telemetries of the LSSB protocol:

  • Telecommands
    • ALC / FGM Command
    • Level / Gain Setting Command
    • Mute ON / OFF Command
    • ARU Enable Command
    • ARU Disable Command
  • Telemetries
    • Level / Gain Step number Telemetry
    • LCAMP Input Power Level Telemetry (in ALC)
    • LCAMP Output Power Level Telemetry (in FGM)
    • Mute Status
    • Temperature Value Telemetry
    • ARC Status
    • Primary Current Telemetry
    • TWT Helix Current Telemetry
    • TWT Anode Voltage Telemetry

Reduce mass and harness / cable effort.


In order to reduce the mass of each harness and to convert most of the parallel signals into serial signals, the Low Speed Serial Bus (LSSB) is intended to be used on future programs.

 click for larger image

  • The Tesat MPM consists of an EPC, a LCAMP (LinCAMP) and a TWT. LCAMP and EPC have individual connectors.
  • Single (one tube, EPC and LCAMP) or Dual models possible (each 2).
  • The LCAMP is designed to work in Ku-, Ka- or C-band. The purpose is:
    • To provide amplification (gain) or power levelling for the tube (TWT)
    • To compensate the TWTA non linearity (linearizer function)

Most of the parallel EPC TM/TC signals are connected over the EPC to the LCAMP now. The LCAMP is converting this signal to the LSSB interface.

A new ASIC is the performing the central management of TM/TC vs. LSSB. The MPM on/off command and the power supply is not part of the LSSB interface.

Current status

EPC to LCAMP interconnection designed/done, new ASIC designed, EPC and 2LCAMPs build and integrated as MPM(TWTA) and in testing. RF testing including LSSB sucessful finished. CDR and final report preparations.