Development and Qualification of an Advanced Pilot Tone Injection Unit (PTIU) and L-Band Test Interface Unit (LTIU) for Next Generation Processed Payloads on Geo-Mobile Communications Satellites

Status date

The PTIU and LTIU are large, multi-way, complex solid-state switch matrices that require excellent phase and amplitude tracking performance.  They enable the functionality of the Next Generation of Integrated Digital Processors using the Alphabus platform (Alphasat Program). The PTIU and LTIU provide critical on-board testing and monitoring functions (phase and amplitude performance) for the large number of signal paths through the digital processors. The Space Electronics Business Unit within COM DEV International Products at our Cambridge, Canada, location will carry out the project.

The first targeted market opportunity for the PTIU and LTIU products is the Inmarsat XL payload currently being developed by EADS Astrium UK, which is to be embarked on the first European Alphabus platform. COM DEV has provided similar products for the Inmarsat 4 series of satellites, however these products must now be redesigned to meet the requirements of the new integrated digital processors and the new Alphabus platform interfaces. In addition, some components and technologies employed in the previous generation of products are now obsolete and must be replaced.

COM DEV’s strategy is to focus on space programs where we have direct channels to the market, and where we have established a good foothold either in advanced payload electronics or other COM DEV product areas.

Potential customers may be grouped into two categories:

  • Satellite Operators/Service Providers
  • Satellite/Payload Prime Contractors

Although product sales such as PTIU and LTIU and related solid-state switch matrices will primarily happen at the prime level, sales and marketing effort is also expended at the satellite operator level to help define future system and subsequent payload product needs.


The following are key issues:

  • Parts obsolescence since the original design was developed.
  • Adapting the Inmarsat 4 designs to the new requirements, with respect to interfacing with a digital processor and the Alphabus payload.
  • The LTIU was not required as part of the integrated payload during Inmarsat 4.



The benefits are as follows:

  • Addressing the market demand for payload equipment onboard mobile communications satellites. Over the past 5 years, there has been strong demand for mobile communications satellites as evidenced by the number of recent programs following Thuraya and Inmarsat 4. According to 2007 Euroconsult reports, this demand is expected to continue over the next 5 years. New mobile satellite payloads will provide opportunities for solid state switching products, such as the PTIU.
  • COM DEV also sees an opportunity for future equipment that performs calibration and monitoring functions related to digital on-board processing. This project will lead to building our heritage and the future ability to collaborate with satellite prime contractors in this area.
  • Continuing development of COM DEV’s solid-state switch matrix products.



Briefly, PTIU and LTIU are large, multi-way, complex solid-state switch matrices that are required to have excellent phase and amplitude tracking performance.

Physically, the units are realized with a base module containing dc power and control functions with two switch matrices, prime and redundant of Left and Right outputs, mounted on top. The diagram below shows an early COM DEV PTIU.

click for larger image

As currently defined, the PTIU and LTIU consist of almost identical hardware. The only difference required in the configuration is that one 3 dB power splitter and one 3 dB power combiner are not needed for the LTIU output cross-strapping. Only the PTIU has cross-strapping at the inputs.

The operating RF frequency ranges for the PTIU and LTIU are slightly different, but with sufficiently broadband circuitry (12% bandwidth with margin) the same circuit elements can be used for both units.

Both units consist essentially of arrays of solid-state switches to form the Left SP64T outputs and the Right SP56T outputs, with appropriate control circuitry, telecommand/telemetry interface circuitry and dc power interface circuitry. The units are developed as internally 2-for-1 redundant; the switching arrays are duplicated with two electromechanical switches used to switch between the prime and redundant sides at one end and 120 combiners are used to join the prime and redundant sides at the other end.


COM DEV has received a contract for work on Alphasat, a major European satellite program being built by EADS Astrium.

Targeted for launch in 2012, Alphasat will be the first satellite to be based on Alphabus, a new European multi-purpose platform for the high-power payload communications satellite market. Alphasat will deploy both a commercial payload for Inmarsat plc and four technology demonstration payloads provided by ESA.

COM DEV will supply high performance power combining networks for the INMARSAT payload. Used in conjunction with Astrium’s next generation digital processor this technology provides unparalleled payload flexibility to the satellite operators in support of existing and future enhanced global mobile satellite services. Work will be carried out at COM DEV’s facilities in Cambridge, Ontario over the next 18 months. The contract includes the potential for follow-on flight set orders out to 2016.

Current status
  • Following the resolution of all issues, the elegant breadboard model was completed and the required updates were incorporated into the design;
  • Equipment CDR held at the end of January 2010 with ESA, Astrium and Inmarsat in attendance at COM DEV Cambridge;
  • All major action items were closed in February with some minor actions remaining;
  • Test stations have been readied for EQM testing and module test procedures are in place;
  • EQM sub-assembly activity is complete and all modules are in test;
  • EQM Delta-TRR planned for week of April 19th to be followed by start of EQM equipment-level formal testing;
  • EQM testing is expected to be completed by the end of May 2010;
  • PFM PCB-level assemblies are well underway.