A New Method of Protecting Against EMI and EMP in Aircraft Applications
In commercial and military aircraft applications, EMC (electromagnetic compatibility) conformity, EMI (electromagnetic interference) and EMP (electromagnetic pulse) protection are paramount to maintaining the integrity of electronic signals, the information that is being transmitted, and consequently the overall performance of the device. Traditional methods of EMI and EMP protection include mounting additional devices to the circuit board. Yet, such solutions are costly, less effective, and do not conform to increasing real estate constraints. Alternatively, inroads are being made in EMI and EMP protection through mounting chip capacitors and TVS devices to flex circuits within a connector — as opposed to the circuit board — to protect against lightning induced transients, voltage surges, and electromagnetic interference and ESD pulses, all while conforming to the cost and size limitations of aircraft applications.
Electromagnetic interference and electromagnetic pulse are factors in the distortion of electronic signals in nearly all commercial and military aerospace applications, as EMI and EMP can distort the signals and cause noise, thereby impacting the information that being transmitted. Because of the nature of the application, navigation equipment, displays, and other electronically transmitted information must be both highly accurate and reliable.
As such, manufacturers are forced to protect against both radiated and induced signal threats. The interconnect system can serve as the gatekeeper into these costly systems that are highly sensitive to voltage induced transients. Protectionis most effective at the interface to the system, placed within the connector. In most of today applications, protection includes capacitive filtering following the protection device to maximize the surge protection to the system. Historically, interconnect manufacturers have been providing solutions within the connectorsthat have been effective but costly.
Traditional EMI and EMP Protection Methodologies
Protecting aircraft electronic systems from lightning transients, voltage surges, EMP, and EMI is traditionally accomplished using one of two methodologies, both of which involve attaching a transorb to every contact in the interface connector.
The first method involves physically attaching a device to the side of each contact within the connector and grounding it to the connector shell. This solution incorporates processes that solder the device and then overmold it to isolate and insulate the poles of the device from each other. Surge and leakage current testing of the contact assembly is always mandatory since the processing greatly affects the performance of the product. The small physical size of the device required to accomplish this method minimizes its power dissipation capabilities and results in a longer connector due to TVSS (transient voltage surge suppression) and filtering.
The second method involves attaching a pre-tested JANTX-certified device with leads to the contact via circuit boards or other similar techniques, the other end being connected to the shell. This method offers the ability to use off-the-shelf devices with a wide range of power handling capabilities. However, the larger physical size of the leaded devices necessitates increased connector size, usually both in length and diameter.