Field Parameter Metrology

Consider the consequences if nearby electronics could interfere with a jet's instruments or cause an automobile to stall. The Field Parameter Metrology Program develops ways of measuring electromagnetic (EM) emissions and susceptibilities to electronic interference of electronic devices and systems. The program maintains the capability to provide EM field measurements.

Applications include the communications needs of first-responders to emergencies, measurements of the shielding effectiveness of advanced materials, effects from and on other electronic components, the statistics of electromagnetic fields in rooms and buildings, and the effects on biological subjects.

This program generates reference EM fields and calibrates EM probes required for their accurate measurement. Accurate EM field measurements are needed to characterize our wireless world and ensure that the valuable electromagnetic spectrum is optimally used, that electronic systems are compatible and neither sources nor victims of EM interference, and that people are not exposed to hazardous fields. As instrumentation and electronics achieve higher clock rates, EM field parameter metrology is needed at ever higher frequencies. The program is working to extend current methods and facilities to higher frequencies, and develop new test methods to increase accuracy and reduce measurement costs.

The program is working on extending open area test site test methods to frequencies above the 1 gigahertz specified by most international electromagnetic compatibility (EMC) standards. Fully anechoic chambers are accepted as standard sites for approximate free-space measurements. Time-domain methods are being studied as a way to measure the characteristics of these rooms and to improve the results obtained therein. This type of chamber is also being evaluated for EMC product testing up to 40 gigahertz. Closed test systems such as transverse EM cells have been widely adopted for testing small antennas, sensors, and probes, but are normally limited by geometrical constraints to below 1 gigahertz. EEEL recently finished construction and testing of a new closed-cell co-conical geometry system that can be used to test such devices up to 45 gigahertz. This new test fixture reduces test times from weeks to hours.

The program provides information to standards organizations to help correlate measurements between various EMC test facilities. The program also cooperates with the national test laboratories of our international partners to perform round-robin testing and comparison of standard antennas and probes. This assures international agreement in their performance and reduces the uncertainties in the areas of metrology that affect international trade. Our goal is to develop and evaluate reliable and cost-effective standards, test methods, and measurement services related to complex EM fields for EMC of electronic devices and other applications in health, defense, and homeland security.

• Completed a co-conical field generation system (CFGS) for the Air Force. The CFGS will reduce hazard probe calibration times from weeks to hours.
• Completed and documented high intensity radiated field (HIRF) shielding effectiveness tests on representative commercial aircraft (Boeing 737-200, Boeing 767-400ER, Bombardier Global 5000, Beechcraft Premier 1A Composite Business Jet); the results were delivered to the FAA.
• Descibed analytically and verified experimentally a new method to quantify the shielding effectiveness of physically small but electrically large enclosures (e.g., instrument and computer housings) in reverberation chambers; introduced the method into the applicable IEEE standard.

Associated Publications/Reports:

• K. Remley, G. Koepke, C. Holloway, C. Grosvenor, D. Camell, J. Ladbury, D. Novotny, W. Young, G. Hough, M. McKinley, Y. Becquet, J. Korsnes, “Measurements to Support Broadband Modulated-Signal Radio Transmissions for the Public-Safety Sector,” NIST Technical Note 1546, April 2008.
• C. Grosvenor, D. Camell, G. Koepke, D. Novotny, R. Johnk, “Electromagnetic Airframe Penetration Measurments of a Beechcraft Premier 1A,” NIST Technical Note 1548, August 2008.
• D. Camell, R. Johnk, D. Novotny, C. Grosvenor, “Free-Space Antenna Factors Through the Use of Time-Domain Signal Processing,” in Proc. 2007 IEEE International Symposium on Electromagnetic Compatibility (Honolulu, HI), pp. 1-5, July 2007.