MIL-STD-461
MIL-STD-461 is an EMI/EMC standard for developmental test and evaluation. This standard is broken out into nineteen various methods. These methods include Radiated Emissions, Conducted Emissions, Radiated Susceptibility, and Conducted Susceptibility.
MIL-STD-461 testing includes radiated and conducted test methods. These methods involve simulations of magnetic, radio frequency, Electrostatic Discharge (ESD), and Electromagnetic Pulse (EMP) sources of potential disturbance. Susceptibility requirements are determined by type of equipment, type of platform the equipment is to be operational on, and location of the equipment on that platform.
RE102 Radiated Emissions Testing
RE102 is the MIL-STD-461 method for evaluating electromagnetic field radiated emissions from systems and subsystems enclosures and cabling designed for U.S. military applications. Requirements and testing to this military standard vary for platform of intended installation. The frequency ranges applicable for various platforms are:
- Ground: 2 MHz to 18 GHz
- Surface Ships: 10 kHz to 18 GHz
- Submarines: 10 kHz to 18 GHz
- Aircraft (Army and Navy): 10 kHz to 18 GHz
- Aircraft (Air Force): 2 MHz to 18 GHz
- Space: 10 kHz to 18 GHz
By the numbers, limits imposed on emissions are severe and well below most commercial standards. The numbers however, do not tell the entire story, because test values measured are peak values, not average or quasi-peak. Measurements are also made with antennas positioned 1 meter away from the edge of the test set up.
In short there is not an apple to apple comparison that can be made between RE102 and other standards; the emission limits are lower, the frequency ranges are larger, and the measurements are performed in a more severe manner.
Special Test Requirements for AIAA S-121A
AIAA S-121 specifies general design practices and sets recommended verification and validation requirements for space vehicles and launch vehicles. This standard can be used for tailoring MIL-STD-461 methods for space applications that may exceed those of MIL-STD-461. This can often be the case for radiated emissions where the limits for certain frequency bands are extremely low.
To achieve these measurements, tailored testing involving scans at reduced Resolution Bandwidths (RBW). Performing these tests requires detailed communications with test facilities to ensure that testing is performable and to calculate required time for test performance.
Getting it Right
While RE102 testing should be performed as early in product development as possible, it is important that the test item be as representative as possible. This means that enclosure, PCB revisions, firmware, software, and cabling should be fully representative of the final product. Care should also be taken in creating the ability to simulate normal modes of operation so that testing can be performed on the Equipment Under Test (EUT) that reflects its intended use.
All of these parameters should be reflected in an Electromagnetic Test Procedure (EMITP) that is constructed in accordance to MIL-STD-461 requirements as described in DI-EMCS-80201. Other important data for inclusion in the EMITP are descriptions of stimulation and monitoring equipment, operating frequencies, performance checks, and a description of cable types complete with construction details.
Facing the Music About MIL-STD-461 RE102
The simple fact is that most product developers do not pass MIL-STD-461 RE102 testing the first time. Retest and redesign cost money and time. Adding patchwork cures such as filtered connectors can add significantly to product cost and often not provide the required attenuation. Often the most cost effective solution is to perform an evaluation of the product to assess sources of the emissions and make design changes to mitigate them before they can couple onto wiring and power sources.
CVG Strategy Experts
Our experts at CVG Strategy have extensive experience in EMI/EMC testing for a number of industries and products, both military and commercial. We also have expertise in testing for space requirements including AIAA S-121A. Our industry experts can assist in developing tailored test plans, test witnessing and troubleshooting. We can also provide design analysis and guidance for product compliance.
Our EZ-test plans are available for military applications for EMI/EMC and environmental testing. Our Electromagnetic Test Procedures are recognized by A2LA Certified Test Labs as reliable and comprehensive. We have included, in addition to guidance from the standards, additions including best practices which we have learned in test program management of equipment designed to Department of Defense standards.
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