NRL Arch Reflectivity Test - IEEE

NRL Arch Method – High-Frequency Testing

This method was originally designed at the United States Naval Research Laboratory in 1945 for measuring the angular-dependent performance of broadband Radar Absorbing Materials (RAM).

The Naval Research Labs (NRL) utilize the swept-frequency arch method to evaluate the reflectivity performance of microwave absorbers for ETS-Rantec, with tests ranging from 1 to 18 GHz. Emctest Technologies can perform this kind of test with the possibility of extension up to 40 GHz upon request.

The approach involves using a non-reflective arch equipped with two horn antennas, positioned internally near its apex, and a metal plate as the 0-dB reflectivity reference beneath the center of the arch. Anechoic absorbers on the ground and rear walls eliminate unwanted reflections. The setup, which includes measuring the reflected energy before and after placing an absorber on the plate, allows for the calculation of the absorber's reflection coefficient.

Reflectivity, defined as the reduction in reflection power caused by the introduction of a material, is measured by comparing reflections from a metal plate and radar absorbing material (RAM) across a wide frequency spectrum, thus establishing the "zero" or 0 dB level. This parameter is used to replicate a condition where a radio wave disperses in space. The use of a vector network analyzer, a time-domain gate, and anechoic panels helps to eliminate interference and noise, enabling a detailed analysis of reflective properties from various angles.

The EMCTEST Technologies laboratory has the NRL Arch device to conduct these tests on absorbing materials.