Defense Intelligence Reference Document Pulsed High-Power Microwave Source Technology

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Figure 7 is a closeup photograph of the same actual components as built and tested at
the High Energy Research and Test Facility antenna range. This source was used
extensively for testing in the 1990s, including remote tests in which the entire system,
including the antenna, a screen room, and far-field diagnostics, was fitted into a trailer
specially modified for the purpose.
Figure 7. HS Output Section With the Point Geometry Converter Feeding an Extended-
Ground-Plane Antenna Through a Brewster Angle Window
THE PHOENIX HPM SOURCE
The Phoenix was a UWB source developed by the AFRL specifically for asset testing at
the High-Energy Microwave Laboratory (HEML). The HEML has a large anechoic
chamber and is capable of testing small fighter aircra~. The Phoenix had a ferrite core
transformer-based system using two flowed oil switches to generate the fast rise-time
voltage pulse. It was bulkier than the H-series sources and thus was less portable. An
oil-processing platform with 1-micron filtering and a 5-horsepower DC motor driving the
positive displacement oil pump was used. The pumping system was capable of a 7-
gallon-per-minute flow rate through the two switches. The oil switches were designed
into son parallel-plate transmission lines. The peaking switch electrode spacing was
only 0.015 to 0.020 inches and was highly overvolted. The operating voltage was about
500 kV with a 90-ps rise time and a 1.25-ns pulse width. The peak power was 5 GW,
and the radiated field at 9 meters was 45 kV/m, giving it an FOM of more than 400 kV.
Phoenix had the fastest rise time of any HPM source to date. Figure 8 shows the
waveform of the radiated field at a distance of 8.5 meters. Figure 9 shows the resulting
spectral content. Note that the source has good spectral content beyond 2. 5 GHz owing
to the extremely fast rise time.
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