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Study for Space Electronics Electromagnetic Mitigation, 15-9533

Principal Investigators
James Johnson
Jay D. Thomas

Inclusive Dates:  02/15/05 – 06/15/05

Background - Deteriorating electromagnetic interference (EMI) performance for Space Systems Command and Data Handling Systems (C&DHS) was traced through several programs that shared a common design heritage. As a result, whenever our clients discussed follow-on programs, EMI performance was frequently labeled as a significant program risk. Because of the immediacy of impending program negotiations (Wise and Hubble), we sought and received internal research support in as attempt to permanently retire the issue.

Approach - We employed a multistep process to highlight common characteristics, parameters, and conduits as appropriate. Our goal was to identify the EMI design shortcomings and recommend improvements wherever possible. Our approach included the following:

• Data Analysis – Perform a top-level analysis of heritage designs and previously reported EMI test results. Identify design deficiencies and postulate improvement methods. Also, identify discrete parameters that contribute to EMI outages to scope radiated and conducted emissions testing to be executed in later tasks.
• Design of Experiment – Formulate an experiment to characterize EMI and impact (if any) of altering the chassis configuration, EMI shielding placement, and other recommended alterations as required.
• Experiment Development and Preparation – Acquire, fabricate, and set up test support equipment. Develop methods to replicate any operational modes previously identified.
• Radiated EMI Experiment, Profile, and Evaluation – Set up and execute baseline EMI profile measurements of the radiated parameters identified in previous tasks. Evaluate the results and ascertain the need to execute targeted conducted emissions testing.
• Optional Conducted Emissions Experiment – Set up and execute baseline EMI profile measurements of the conducted parameters identified in previous tasks.

Accomplishments - Our analysis of heritage designs revealed several violations of "best EMI engineering practice." The focused analysis resulted in approximately 30 recommendations to improve EMI design – approximately 17 of which have direct impact on board design. Our EMI experiment revealed shortcomings in both EMI filtering application and employment of free-space attenuation opportunities. The radiated emissions data findings and follow-on analysis included one specific design change recommendation and a recommendation for programmatic philosophy changes to support the design change. The conducted emissions data findings and follow-on analysis included identification of a commercial off-the-shelf (COTS) product to improve our EMI performance and two recommendations for additional investigation.

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