Electromagnetic Vulnerability Assessment Facility (EMVAF),
White Sands Missile Range, New Mexico

Army Humvees inside the EMVAF main anechoic chamber; the floor absorber has been removed for test setup.
    Image courtesy Army Research Lab

A Specialized Facility for High-Power Microwave Susceptibility Tests

Since its completion in 2007, the EMVAF has been the US Army's premier facility for RDT&E programs that address the electromagnetic survivability and vulnerability research objectives of the Army as well as other branches and DoD activities. (Click here and here for news stories and photos about EMVAF's opening.) The facility design project, in which The Howland Company played a central role in communicating user requirements to facility architects and designers, was named one of the top Architect-Engineering firm projects for 2006 by Southwest Contractor magazine.

 

 

"The recently established Electro Magnetic Vulnerability Assessment Facility (EMVAF) is a state-of-the-art facility with the goal of evaluating and investigating antenna performance, vehicle effects (jamming and communication), and multipath effects. The facility is impressive, well designed and managed, and well staffed by dedicated and energetic personnel. The management should be commended for conceiving, designing, and developing this facility, which serves many critical missions and needs of the Army. SLAD has increased its ability to maintain a leading edge for this sort of analysis."

    -- 2009-2010 Assessment of the Army Research Lab, National Research Council


"[The] Electromagnetic Vulnerability Assessment Facility (EMVAF) [is] used to sustain the Army Research Lab’s ongoing mission to evaluate Army weapon systems’ survivability against the full spectrum of electromagnetic energy threats on the battlefield and in operations other than war (OOTW). This includes the means to determine weapon systems’ survivability against radio-frequency directed energy weapons."

   -- US Army White Sands Missile Range website

 

 
 

In Focus :

One of the unique capabilities of EMVAF is its ability to create a GPS environment, with either simulated or real-world GPS signals, that is electromagnetically isolated from the outside world. This permits testing of GPS jamming technologies with no risk of interference to GPS users in the WSMR neighborhood, as well as assessment of current or under-development systems' ability to use GPS when jamming is attempted.

So the central role EMVAF is playing in the DoD's development of Assured Positioning, Navigation and Timing (A-PNT) is no surprise. This article reports on a recent testing program which "concentrated on Pseudolite performance at various jamming, or interference, levels as well as risk reduction elements to prepare for future field tests. Secondary test objectives, to include anti-jam antenna system (AJAS) and receiver (e.g., military legacy, commercial, and Pseudolite enabled) system performance, were also observed."

Pseudolite prototype systems were tested within the anechoic chamber to better understand transmission capabilities, navigation abilities, interference thresholds, and overall performance. The chamber is the Army's largest anechoic chamber providing an ideal work place for applied research, development, test, evaluation, and experimentation.

 
     
 

In Focus :

The EMVAF facility and its experienced staff supported a series of tests to assess the impact on existing GPS systems of LightSqared's proposed satellite and terrestrial broadband network. Testing was conducted in the summer and fall of 2011, with results published early in 2012. EMVAF's unique characteristics allowed a comprehensive test program that would have been impossible to accomplish elsewhere without disruption of GPS navigation and tracking systems. Some photos of the testing:

 
 
Commercial/civilian GPS equipment setup for assessing vulnerability to interference from LightSquared transmit antennas and handsets.  Engineers and technicians monitoring LightSquared interference tests, EMVAF, White Sands, late 2011.
 
  The successful test program was a combined effort of the military, the FAA, the National Telecommunications and Information Administration (NTIA), and equipment vendors, all under the auspices of the National Space-Based Positioning, Navigation, and Timing Systems Engineering Forum (NPEF).  
 


The EMVAF facility includes two shielded anechoic chambers: a 100 ft x 70 ft x 40 ft (30m x 21m x 12m) optimized for high-power microwave test and measurement of air and land vehicles, and a smaller 20 ft x 30 ft x 20 ft (6m x 9m x 6m) chamber for smaller DUTs. The large chamber has a 100-ton capacity turntable and and a heavy-duty bridge crane hoist; it has two large 100 dB RF shielded doors, one 14 x 14 feet and the other 20 x 20 feet, for test article access. A mezzanine area provides convenient space for test equipment setup and cabling.

The Howland Company worked with the Army's user organization--the Survivability and Lethality Analysis Directorate--and the A/E firm, DMJM Holmes & Narver, to develop a facility conceptual design that would satisfy current and projected requirements. We designed the shielded anechoic chambers and control rooms and the RF shielding for high-security areas. We wrote the procurement specifications for the shielding and anechoic construction as well as the 100-ton capacity turntable. During the construction phase, we advised the general contractor and the Army on issues of construction sequencing; we were also tasked with oversight of the QA program for all shielding and anechoic construction and testing.

The Howland Company also conducted an extensive series of commissioning measurements to characterize the two anechoic chambers. These measurements were made using a Spherical Near-Field Imaging technique. (Technical papers describing the technique and its application are available below.) The Spherical Near-Field Imaging technique affords anechoic chamber designers and users an unprecedented capacity to measure electromagnetic field purity within a specified measuremt volume, and also to identify and mitigate extraneous signals entering the test zone. In the image below, a 3D plot of image data is oriented to match the inset photo of the large EMVAF chamber; all the sources of extraneous reflections into the test zone--sprinkler heads, fiberglass stair rails, walkway absorber--appear very clearly, along with the strength of the reflection in decibels.

Comparison of measured data to chamber photograph: all the sources of extraneous reflection--sprinkler heads, fiberglass handrails, walkway absorber--appear clearly in the processed 3D image.

Download PDF "Recent Advances in Anechoic Chamber Characterization Using Spherical Near-Field Imaging," John C. Mantovani, Carl W. Sirles and Ray Howland, presented at the AMTA Symposium, 17-21 October 2011, in Denver.

Download PDF "Anechoic Chamber Performance Characterization Using Spherical Near-Field Imaging Techniques," Carl Sirles, John Mantovani, Ray Howland, and Beau Hart, presented at at EuCAP2009, the 3rd European Conference on Antennas and Propagation, 23-27 March 2009, in Berlin.

EMVAF o n the web:

 

EMVAF is managed and operated by the Modeling & Simulation Support Branch, Information and Electronic Protection Division, of the Survivability/ Lethality Analysis Directorate of ARL (AMSRD-ARL-SL-ES). Click the image at right for a PDF data sheet with contact information and a summary of the facility's capabilities. See these sites for more information:

 

EMVAF Facility Data Sheet (383kb PDF)

SLAD logo

ARL logo

ARL Survivability/Lethality Analysis Directorate

Doing Business with ARL

ARL White Sands Visitors' Guide

 
EMVAF construction   EMVAF construction
    Images courtesy Pikes Peak Steel

Two images of the EMVAF under construction. In both photos, the sheet metal and framing for the outer
RF shield welded enclosure is visible inside the framing for the host building. Placing EMVAF's anechoic
chambers inside this outer envelope provides an additional layer of physical and electromagnetic security.