Documents / Official release
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/ j FOR OFFICU!tt l:191!!! 9HL'f (a)Figure 13 shows (a) Vlasov antenna orig ins and (b) a Vlasov antenna attached to a cylindrical MILO. Vlasov antennas have one major drawback: the propagation angle is a function of the operating frequency. Thus, if the frequency chirps during the RF pulse, then the beam direction will sweep. The propagation angle is given by: lb) 0 = 90° - cos ((1-(fc/f)2) 112) WIDEBAND AND ULTRAWIDEBAND ANTENNAS Wideband antennas generally present a much greater design challenge than do narrowband antennas. As pulse duration um\\i ndow) and rise times are shortened, antenna design becomes more diffi cult. A good Figure 13. (a) Mode Converter Vlasov Antenna and wideband antenna must have low (b) Vlasov Antenna Attached to a Coaxial MILO dispersion across the entire bandwidth and high gain with minimal sidelobes. These are difficult to achieve because the wavelengths are large, requiring large antenna dimensions for high gain. Often, mission constraints dictate a much smaller antenna, thus the gain will not be constant with frequency, resulting in a distorted radiated pulse shape. The main consideration for transmitting UWB signals is minimizing frequency dispersion . For conventional antennas, the gain is a function of frequency. One approach to solving this problem has been to correct a conventional antenna (TEM horn) for dispersion. A second approach has been to use the dispersive characteristics of a conventional antenna, with the appropriate tailored drive signal, to radiate the desired UWB signal. A third approach has been to develop a new type of antenna. These three approaches cover the limited gamut of UWB HPM antennas. The basic approach to attain ing low dispersion in a conventional antenna is to ensure a slowly varying antenna impedance change along the length, beginning at the source output impedance and end ing somewhere close to the impedance of free space (377.0). In practice, it is found that the final impedance does not have to be very close to that of free space; instead, 220.0 to 280.0 provides the highest efficiency for most TEM horns. Best results are obtained for any length TEM antenna if the impeda nce is increased at a constant percentage rate (that is, is exponentially tapered). The resulting design may then have electrical breakdown problems at the connection point with the source, since the antenna impedance changes initially are quite small and, thus, plate spacing also remains small. Typica lly, a specially shaped, solid insulating material is required to obtain a gradual impedance change when transitioning from the source media into air. Th is is where the highest electric field strength is found and also where the temptation to aid impedance tapering by incorporating abrupt transitions in conductor dimensions is greatest. Any reflections of the pulse from farther down the antenna will also enhance fields at the feed point. All these factors combine to make the design of the antenna feed section possibly the most important factor in HPM sources and, in many UNCLASSIFIED//FOA. OliFICil.\k W&lii 8HL\« 27
Not linked to a story yet.
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.