Electric-breakdown and vibration tests were performed on one-patch and two-patch versions of a prototype of a patch antenna designed to radiate a continuous- wave or pulsed signal in the S band (1.5 to 4 GHz) having a spectral width of 420 MHz and a peak power that could exceed 2 kW. This antenna is being developed for military use in neutralizing unattended improvised explosive devices. The patch antenna configuration was chosen for this development because it offers an efficient, less-bulky alternative to a conventional horn microwave antenna design.
The two-patch prototype antenna (see figure) included an antenna assembly in a metal box with a dielectric front cover. The antenna assembly included a power divider, right-angle coaxial connectors, a ground plane, and probe feeds for the two patch antenna elements, plus a coaxial connector protruding from the rear of the box for connection to a microwave power source. The single-patch antenna was similar but simpler; there was no power divider and there was direct probe feed from a rear-surface coaxial connector to the single patch antenna element.
In the electric-breakdown tests, the antennas were run in a pulsed mode at a peak power >2 kW, and a horn antenna a small distance away was used in measuring the radiated power. It was assumed that electric breakdown (arcing), would manifest itself as sudden decrease in radiated power during a pulse. Each antenna was tested at two- and five-minute time intervals. No evidence of arcing was observed. Hence, both antennas were deemed to pass the electric-breakdown tests.
The vibration tests were modified military-standard tests designed to produce vibrational effects equivalent to those of 1,000 km of travel in a tactical wheeled vehicle. For each antenna, there were three vibration tests; in each test, the antenna was bolted to a shaker table in one of three mutually perpendicular orientations. After the vibration tests, the antennas retained their desired radiative and electric-breakdown performance, although nylon screws that held the front cover on the box had become loosened about a quarter of a turn. In the two-patch antenna, the right-angle coaxial connectors attached to the power divider had also become loosened, less than a quarter of a turn. It was found that the loosening could be prevented by securing the cover-retaining screws with floating lock nuts and by applying a thread-locking material to the threads on the right-angle connectors.
This work was done by Canh Ly of the Army Research Laboratory.
This Brief includes a Technical Support Package (TSP).
Arcing and Vibration Tests of High-Power Patch Antennas
(reference ARL-0031) is currently available for download from the TSP library.
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