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This Defense Intelligence Reference Document (DIA-08-0912-005) is dated 28 January 2010. The Defense Intelligence Agency's Defense Warning Office prepared it under the Advanced Aerospace Weapon System Applications Program. It gives an overview of pulsed high-power microwave sources and the technologies needed to build them, including insulation, cathode materials, high-voltage switching, pulse generators and antennas. The paper concludes that progress requires better cathodes, switching and insulation, and that compact ultrawideband antennas will remain difficult to build.
From the source:Release of 2026-09-18 Incident: 1/28/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys pulsed high-power microwave (HPM) source technology and argues that such systems remain of military interest because they can disrupt or damage electronic systems with short, intense electromagnetic pulses. The report reviews the main source types and the supporting technologies they depend on, including high-voltage insulation, switching, cathode materials, antennas, and pulse-power generation. It emphasizes the difficulty of building systems that are compact, efficient, and practical to field, since short pulse durations, antenna size, heating, detectability, and beam or signal quality all impose hard engineering limits. Its overall conclusion is that the technology has significant potential military value, but that further progress depends on advances in cathodes, predictive modeling, high-speed high-voltage switching, and low-loss insulation, while compact ultrawideband systems will remain difficult because of basic physical constraints on antenna design.
UNCLASSIFIED/ /FOR OFFICIAL U.!I! er•tY instances, the determinant of the radiated signal characteristics. Sidelobes generated using TEM antennas tend to fall off sharply and are accompanied by a stretch ing of the original pulse duration. The distance from the antenna to where the far field region begins is defined such that the travel time of the differential distance is less than the rise time of the pulse. Parameters such as gain and beam width for UWB antennas are difficult to define because these concepts are from the narrowband world, where the definitions are for a single frequency. For UWB antenna comparisons, the community uses the previously described figure of merit concept to aid with this problem. The FOM is the peak electric field measured at some distance multiplied by that distance, thus the unit for FOM is volts. Using this concept, gain for UWB antennas is defined as: UWB gain = FOM/Vp where: Vp is the peak voltage of the driving pulse. Typical gains are 3-4 but with extreme designs can reach 6 and above. These are the antennas of choice for impulse radars since they can be small and lightweight but radiate UWB pulses quite well. However, sidelobe pulse stretching makes the aiming accuracy of the transmitting and receiving antennas crucial. Another technique of interest in WB/UWB antennas uses a log-periodic antenna designed with dispersion characteristics such that, when driven with the proper input signal, it produces the fast rise time pulse required. The drive signal in this technique must have a strong increase in frequency from start to end. No high-power designs using this technique appear to have been accomplished. A new type of antenna, the impulse radiating antenna (IRA), incorporates a parabolic dish as a main component of the design (in fact, it is debatable whether this is actually a new design because it incorporates a parabolic dish). The distingu ishing feature of an IRA is its use of a final fast switch located at the focal point of the dish to provide a spherical waveform to the dish. The design also must include a high-voltage transmission line to feed the peaking switch, which in all probability will not be dispersionless. However, the frequency content of the feed signal most likely will be less than that of the wave front from the peaking switch. The design also must include some number of conical transmission lines from the peaking switch back to the dish, providing something close to an impedance match for the feed pulser. The crucial criterion here is that the IRA be driven by a spherical TEM wave front, in which case the phase center of the wave is then fixed and the IRA is dispersionless . There is also a much smaller pre-pulse that is radiated from the front side of the switch and is not reflected from the dish. This signal will be radiated two focal lengths ahead of the main pulse . For a 4-meter dish, the pre-pu lse arrives about 10 ns before the main pulse . Fast-acting semiconductor protection devices could in principle be effective in negating the effects of the main pulse. The peaking switch at the focal point must be contained in some insulating media and, thus, there is a reflection associated with the transition to air. The wave front generally is not spherical as it enters the air beyond the peaking switch owing to the physical dimensions of the switch and high-voltage insulation requirements. Successful IRA designs use the switch insulating media and container to form a lens designed to give a spherical wave at the air interface. The IRA, like the TEM horn, transmits a differentiated signal from the applied pulse. This is why the rise time of the driving pulse is so important to antenna response. UNCLASSIFIED/ /FOR OFFICIO! 1!iii ODIL¥ 28
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 37 pages are in the text index: search them above, or from the library's search.