Abstract
Performance evaluation is an important aspect in the study of microwave-absorbing material coatings. The reflectivity of the incident wave is usually taken as the performance indicator. There have been various methods to directly or indirectly measure the reflectivity, but existing methods are mostly cumbersome and require a strict testing environment. What is more, they cannot be applied to field measurement. In this paper, we propose a scheme to achieve field performance evaluation of microwave-absorbing materials, which adopts a small H-plane sectoral horn antenna as the testing probe and a small microwave reflectometer as the indicator. When the size of the H-plane sectoral horn antenna is specially designed, the field distribution at the antenna aperture can be approximated as a plane wave similar to the far field of the microwave emitted by a radar unit. Therefore, the reflectivity can be obtained by a near-field measurement. We conducted experiments on a kind of ferrite-based microwave-absorbing material at X band (8.2–12.4 GHz) to validate the scheme. The experimental results show that the reflectivity is in agreement with the reference data measured by the conventional method as a whole.
Highlights
Absorbing materials refer to those materials that can absorb the electromagnetic energy projected onto their surfaces, and transform the electromagnetic energy into heat or other forms of energy.With the development of science and technology, electronic products are widely used in production and life
We propose a scheme to evaluate the performance of microwave-absorbing material on site, which adopts a small H-plane sectoral horn antenna as the testing probe and a small microwave reflectometer as the indicator
We find that the field distribution at the aperture of the H-plane sectoral horn antenna can be approximated to a plane wave when the size of the horn is specially designed
Summary
Absorbing materials refer to those materials that can absorb the electromagnetic energy projected onto their surfaces, and transform the electromagnetic energy into heat or other forms of energy. The calculation is time-consuming, and measurement errors of the permittivity and permeability can lead to an incorrect calculation of reflectivity What is more, they cannot be used in field measurement. In the arc-frame method two movable pyramidal horn antennas are mounted on an arc-frame to measure the reflectivity, and the absorbing-material coating is fixed on the desktop. Among these methods, the arc-frame method is widely recommended. Known as the NRL arc-frame technology [6], this method was originally developed by the Naval Research Laboratory of America It can obtain the reflectivity of the absorbing material directly, but requires a strict testing environment. The designed testing system is portable and especially suitable for field measurement
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