Online Journal of Space Communication

Article Title

Baseband Processor Hardware for Advanced Communication Technology Satellite (ACTS)



Motorola has developed a satellite baseband processor (BBP) for NASA Lewis Research Center's Advanced Communication Technology Satellite (ACTS) program. The objective of the ACTS program is to develop the high risk advanced communication technology required for future satellite systems and to promote effective utilization of the spectrum and growth in communication capacity.

Key features for this next generation satellite communication system include coverage of the contiguous United States through a control switching satellite in time-dimension, multiple-access (TDMA) mode. The use of Ka-band (30 GHz on the uplink and 20 GHz on the downlink) presents frequency reuse on a geographic basis because of the narrow beam scanning antenna.

The baseband processor developed by Motorola provides the flexible message routing capability needed to support the satellite's TDMA burst communications. Key technologies developed for the ACTS BBP included coherent serial minimum shift key (SMSK) burst demodulators, a family of high speed, low power large scale integrated (LST) circuits, a maximum-likelihood convolutional decoded (MCD) on a single LSI chip, and the development of memory architectures using programmable control memories.

This paper gives a brief overview of the ACTS Multibeam communication package (MCP) payload, the Baseband Processor (BBP) subsystem description, baseband processor development history leading up to the ACTS BBP, and key technologies developed for the ACTS BBP. ACTS BBP functional description describing how hardware is partitioned into subassemblies (referred to as boxes) is presented.

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