Plasma arc test technique for evaluating antenna window RF transmission performance

A test technique is presented to make both qualitative and quantitative measurements of the RF transmission characteristics of a material when heated to temperatures up to and including the ablation temperature of window material. The high temperatures and ablation are produced by a plasma arc, and active transmission through the window material is accomplished before, during and after arc operation. Materials are exposed to heat fluxes as high as 3000 BTU/sq ft-sec. A data reduction technique is used to obtain quantitative values for the material loss tangent versus temperature, and the technique can assess the potential of new materials for antenna windows for vehicles with severe heating environments.