Introduction
While many may be concerned by an outright nuclear attack on US soil, the emerging clear and present danger predicted by government and private think tanks is Electromagnetic Pulse (EMP) threats. Such a threat, carried out by strategically placed land devices, could be catastrophic to virtually every facet of our civilization. Organizations both public and governmental have become aware of such threats for several decades, and it’s only recently that we as a nation have realized the extent and severity of EMPs.
Categorized as Intentional and Unintentional Electromagnetic Interference (IEMI/UEMI), these threats can interfere with and damage critical facilities, aerospace, infrastructure, and land mobile electronic systems. Most nations are currently vulnerable to sabotage and the intentional disruption that IEMIs can create. It’s no secret that devices and systems have become vulnerable to IEMIs/UEMIs created by EMPs. Perhaps equally disruptive is the new threat to digital and communications networks. These data centers and internet systems form the linchpin of the world’s banking, transportation, and resource allocation.
The Rising Need for EMP/ HEMP Filters
Early efforts to protect buildings and racks of electronic equipment have given way to a new breed of EMI filters. These EMP/HEMP or IEMI filters are designed to protect specific electrical assemblies, or sub-assemblies from IEMIs. All have been designed to ensure that susceptible electrical/electronic systems remain survivable and able to suppress harmful EMI.
Historically, standards were developed for large rack based and enclosure-based electronics. Current EMP filters are designed to absorb potentially destructive overshoot voltages and work to meet MIL-STD-188-125 requirements. Should a voltage overshoot exceed the switching voltage, the filter suppression circuitry switches to a low impedance, high attenuation mode to short the excessive voltage and absorb the excess energy inside the filter. Today’s EMP filters must protect small critical systems at the device or assembly level. Such electronic systems may not have long runs of electrical conductors and may be susceptible to E1 and E2 pulses. These concerns precipitated the development of IEMI filters enhanced for EMP/HEMP applications.
• Standard Control/Signal Line HEMP Filters
These filters comply with paragraph 4.6.1 of MILPRF-15733 for visual and mechanical inspection standards, and their capacitance meets method 305 of MIL-STD-202 at 1 kHz. Their insulation resistance complies with paragraph 4.6.7 of MIL-PRF-15733 with the HEMP protection module removed, and their dielectric withstanding voltage complies with MIL-PRF-15733 with the HEMP protection module removed. They also meet MIL-STD-220 requirements for a standard insertion loss of 20 dB at 10 kHz and 80 dB at 10 MHz to 10 GHz.
• High-Performance Control/Signal Line HEMP Filters
These filters come with a voltage rating of 48 VDC and 120 VAC between 0 and 60 Hz. They comply with paragraph 4.6.1 of MIL-PRF-15733 for visual and mechanical inspection standards and their capacitance meets method 305 of MIL-STD-202 at 1 kHz. Their insulation resistance complies with paragraph 4.6.7 of MIL-PRF-15733 with the HEMP protection module removed, and their dielectric withstanding voltage complies with MIL-PRF-15733, paragraph 4.6.5 with the HEMP protection module removed. They also meet MIL-STD-220 requirements for high-performance insertion loss for 100 dB at 14 kHz to 10 GHz.
