A small silicone disc helps military and aeronautical equipment live up to stiff electromagnetic compatibility standards.

Helicopters, drones, airplanes trucks, and ships are tough on the outside, but their internal electronics are extremely sensitive. Because these vehicles can be exposed to harsh physical and electrical environments, they can’t afford to fail—and they face bigger challenges than their counterparts that operate in smoother conditions. As such, supressing the electromagnetic interference (EMI) that threatens aeronautical and military equipment requires heavy-duty mitigation measures.

The Electromagnetic Compatibility (EMC) standards that define EMI emission limits and immunity levels are exceptionally stringent, due to the demands posed to equipment that must operate reliably in the air, sea, and deserts. EESeal® filter connector inserts from Quell offer a durable and cost-effective approach for protecting equipment from unwanted electrical currents in harsh environments.

Designing Electronics for a Noisy World

Electromagnetic waves external to a device introduce unwanted currents in a way that disrupts the desirable current, reducing performance quality and causing malfunction. This electromagnetic noise or interference can be natural—from lightning and solar storms, for example—or human-generated, by high-power radio or electrical sources, even everyday handheld electronics. Noise can also be emitted by other parts of the device itself.

The first level of defense against EMI is metallic screens that surround the electronics and reflect or absorb EMI transmitted through the air, but its effectiveness is limited. EMI filters, in contrast, can fully eliminate interference frequencies. Filtering uses circuits designed to reduce the high-frequency noise conducted through electronic equipment, blocking signals above a
certain frequency, and allows lower frequencies to pass through, ensuring that only desirable currents can flow freely.

In the military, both moving and stationary infrastructure house sensitive electronic systems that need to operate seamlessly when exposed to shocks, fluid immersion, intense vibration, or relentless saltwater spray. Communications systems are especially vulnerable due to their delicate electronic circuitry. At the same time, radio and telecommunication devices are paramount to human safety and mission success. Mission-critical equipment can also fail when exposed to weaponized EMI: high-powered electromagnetic pulse threats designed specifically to do harm to the enemy’s equipment.

When Devices Fail EMI Compliance Testing

Given all of these concerns, compliance standards are stringent. Testing processes for electronic equipment involve lengthy preparation and design upgrades, and a failed EMI test can halt operations altogether.

The traditional approach to managing interference is installing connector components that filter electrical signals at equipment entry points. The filter’s electronic contacts detect and attenuate specific frequency ranges, preventing it from entering the equipment. Traditional filtered connectors use standard designs, are fully configurable, and perform well to attenuate emissions.

On the other hand, adding manufacturer filter connectors is expensive and complicated, especially if they are to be added after prototype testing has already begun. Similarly, it can take a lead time of weeks or months to acquire a filtered connector. Then, it can take months again to spin the board or design to accept it and re-test the equipment until standards are met.

Fortunately, there’s a simpler alternative: a rubber seal embedded with passive chip components like capacitors and inductors, which fits between the two mating surfaces of any host connector. One EESeal can help devices pass compliance tests without any redesign needed. The silicone rubber protects and suspends the chip components, protecting them from harsh environments. The slip-on disk is quick and easy to install by hand to existing connectors, adds less than one gram of weight, and takes up negligible space.

Filtering EMI Noise and Adding Value

An EESeal filter insert offers a reversal of fortune for failed EMI tests or mid-development design changes. The silicone seal substrate fits over the pins of a pin-and-socket connector with precision. The insert stretches and compresses to ensure a tight connection. Gold-plated wires or conductive silicone connect the embedded chip components to the connector pins and the shell. Each pin can be treated uniquely by selecting the individual electronic components (typically 0402 and 0603 package components) for exact requirements. A filter insert can easily retrofit existing connectors of any type. Quell offers rapid prototypes designed to solve specific problems, delivered within days, not weeks.

Installing a filter insert simply involves sliding the rubber disk over the connector pins, without the need of soldering or tools. The seal created during the compression reduces the filter’s size. The design avoids air pockets, maintains the existing environmental seal, and morphs into a shape that mimics the connector interface.

Saving Time and Cost on Big Projects

Recently, EESeal filter inserts helped bring an aerospace client into compliance with EMC qualifications as determined under MIL-STD-461 testing. The client needed a quick and simple way to eliminate radiated emission in the 50 to 200 MHz range that was measured in a radio during testing. Working with Quell engineers led the client to a custom EESeal product that provided targeted attenuation within this frequency range. The filter insert brought the product into compliance without additional circuit designs, prototyping runs, or simulations. Ultimately, radiated emission from the product was barely distinguishable from ambient background noise.

Take a closer look at how the EESeal was effectively integrated into four additional mil/aero applications, including missile guidance, a satellite, an infrared system, and a helicopter. Watch the video below for details.

In all four cases, EESeal was able to provide the necessary mitigation and meet compliance standards despite exceedingly harsh conditions.

The EESeal filter insert uses patented electronic packaging technology to suspend, isolate, and protect components. Environmental and mechanical stress tests show that even severe environments do not affect its integrity. The design stands up to criteria established via Mil-Std-461 for military and defense applications equipment, including resistance to shock, vibration, salt spray, thermal cycling, humidity, temperature-altitude, fluid immersion, fungus, and outgassing. It can help solve FAA/DO-160C issues for aerospace equipment as well. For almost all connectors, the EESeal attenuates frequencies from 100 KHz up to 100 GHz, by up to 45 dB.

EESeal filter inserts are durable, tested, and well-proven products that offer advantages over standard filtered connectors. What started as a rapid fix for EMI protection has now made its way into early design phases by large manufacturers. The robust insert holds up in the harsh environments required by military and aeronautical equipment. In the words of Quell, an insert “makes it easy to turn any connector into a filtered connector.”

Request your free custom sample from Quell today.