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Hardened Tuned-Wall Plastic Radomes for Military Radars
ARMY MATERIALS AND MECHANICS RESEARCH CENTER WATERTOWN MA
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XP stretched polypropylene film is perhaps the most effective material for construction of hardened dielectric walls. It has excellent fragment-defeat properties, a low relative dielectric constant 2.3 and a very low loss tangent 0.005. For low-loss materials, reflection losses are determined by the dielectric constant and absorption losses by the loss tangent. A perfect radome material would have a dielectric constant of one and a loss tangent of zero. Additionally, XP is self bonding under heat and pressure, allowing construction of homogeneous, tuned-wall design. The wall thickness is chosen to be an integral number of half wavelengths in the material to take advantage of canceling out reflections at the inner wall loss in beam intensity is then mainly due to absorption in the wall. 1 The resulting thick- wall radome allows efficient r-f transmission and provides a high level of ballistic protection against fragmentation munitions. The ANTPQ-37 is the first radar antenna considered for hardening against fragment munitions attack.
APPROVED FOR PUBLIC RELEASE