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	SwRI engineers used custom-designed pneumatic controls (top) to remotely control this vehicle while being tested for radiated immunity to electromagnetic fields.

Southwest Research Institute (SwRI) has extensive electromagnetic compatibility (EMC) facilities and equipment that, combined with an experienced staff, provide unique capabilities to assist clients during product development. Since 1956, SwRI has developed EMC standards, specifications, hardware, and software for a variety of applications.
 

SwRI provides EMC services at its extensive facilities in San Antonio, Texas, or at the client's facility. SwRI conducts tests and evaluations to industrial, military, national, and international standards. The Electromagnetic Compatibility Research (EMCR) Section of SwRI is qualified by the American Association for Laboratory Accreditation (A2LA) to the ISO 17025 for electromagnetic compatibility design, testing, and analysis. In addition, the EMCR is recognized for testing automotive electronic components in accordance with the Automotive Electromagnetic Laboratory Accreditation Recognition Program (AEMCLRP). Members of the EMCR staff are certified EMC engineers and technicians by the National Association of Radio and Telecommunication Engineers (NARTE), Inc.
 

	Using a ceiling-mounted aluminum stirrer turned by a pneumatic motor, the SwRI stirred mode facility efficiently tests whole vehicles and smaller systems. The position of the stirrer is monitored through a fiber-optic link.

EMC Test Facilities

Stirred-Mode Chamber

SwRI designed the stirred-mode chamber facility to accommodate testing of the whole vehicle as well as smaller components and subsystems. The stirred-mode facility provides highly efficient immunity testing because the device being tested is immersed in a quasi-homogeneous electric field. This evaluation method minimizes test time and costs.
 

Shielded Enclosures

SwRI EMC facilities include 8 shielded enclosures, ranging in size from 10 feet x 20 feet x 10 feet to 20 feet x 30 feet x 12 feet. All enclosures have filtered 120/208 three-phase 60 Hz power, with 50- and 400-Hz power available, and can be configured with RF absorptive material. Two sets of enclosures share a common wall. Each enclosure provides:

• 100 dB of attenuation to electric fields from 1 kHz to 25 MHz

• 100 dB of attenuation to plane waves 25 MHz and above

• 20 dB H-Field attenuation at 1 kHz increasing to 100 dB at 150 kHz

Radio Frequency (RF) Anechoic Chambers

SwRI has an anechoic chamber available for EMC tests and evaluations. It measures 28 feet x 16 feet x 16 feet and provides RF attenuation in excess of 100 dB, 30 MHz and above. This facility can be fully configured with anechoic material or used without the material on the floor to expose the ground plane.
 

Open-Area Test Site

SwRI maintains an open-area test site (OATS) to measure radiated emissions from electronic and electrical equipment. The level test site is clear of electromagnetic reflecting surfaces for a minimum radius of 32 meters. Three-phase 60 and 400 Hz, single-phase 50 Hz, and DC power sources are available to test systems. The open-area teset site has a large, continuous metal ground plane (20 x 40 meters) and a 4-meter diameter flush-mounted turntable capable of supporting 15,000 pounds to conduct tests in accordance with:

• ANSI C63.4

• CISPR

• IEC

• ISO standards

	The Tri-plate-line is used to test small assemblies such as automotive electronic components for immunity to radiated electromagnetic fields.
	To understand complex electromagnetic compatibility interactions, engineers use sophisticated modeling algorithms. This planewave simulation at the interface of two media shows that the incident and reflected fields on the left side interfere with the surface wave on the right (plot of magnitude versus position).

Tri-Plate-Line Fixture

A Tri-plate-line (TPL) test fixture, designed and built by SwRI in accordance with SAE specification SAE J1113-25, is used to conduct radiated immunity evaluation of various automotive modules, sensors, and subsystems and their associated wire harnesses. The TPL is used to generate E-fields in excess of 400 volts/meter from 1 MHz to 200 MHz and 200 volts/meter from 200 MHz to 1 GHz.
 

Transverse Electromagnetic (TEM) Cells

SwRI has three TEM cells ideal for EMC testing of small modules and brass board prototypes. The largest cell operates over the frequency range of DC to 220 MHz. SwRI built two additional cells to the Crawford cell design; one operates from DC to 500 MHz, and the other, from DC to 1 GHz.
 

EMC Development Activities

SwRI EMC engineers and technicians, certified by NARTE, Inc., perform tests on electronic devices to detect and measure electromagnetic emissions and to identify susceptibility/immunity problems associated with radiated electromagnetic fields. SwRI engineers then can suggest electronic design modifications to remedy EMC noncompliance.
 

SwRI engineers used custom-designed pneumatic controls (top) to remotely control this vehicle while being tested for radiated immunity to electromagnetic fields.
 

Using internal funding, SwRI develops improved EMC test equipment, special-purpose test systems, and novel testing techniques. SwRI staff members have developed direct RF injection techniques and developed stirred-mode test chambers.
 

For more information about electromagnetic compatibility capabilities and facilities at SwRI or how you can contract with SwRI, please contact Jenny Ferren at jferren@swri.org or (210) 522-2329.  We can offer you insights about how to specify the best approach to solving your EMC problem.

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

June 26, 2008