A Polarization-Insensitive Band-Notched Absorber for Radar Cross Section Reduction

A polarization-insensitive broadband absorber with a notch band characteristic has been presented for radar cross section (RCS) reduction applications. The proposed design is a three-layered structure, consisting of metal-printed substrate layers separated by air spacers. The top layer is a resistor-loaded convoluted cross-dipole geometry that results in a wideband absorption. The band-notch response is achieved by careful design of a square loop in the middle layer, and the bottom layer is a complete metal ground. The overall structure exhibits two discrete absorption bands (having absorptivity above 90%) over the frequency ranges of 2.12 to 4.15 GHz and 6.08 to 9.58 GHz, whereas a reflective behavior is obtained from 4.3 to 5.65 GHz. The proposed geometry has several novel features, such as compact topology (with unit cell size of 0.137 λL, λL being the lowest operating wavelength), low profile, polarization-insensitivity, and wide operating bandwidth of 127.52%, unlike the existing band-notched absorbers. By deriving an equivalent circuit model and several parametric variations, the performance of the proposed absorber has been qualitatively analyzed. A sample prototype has also been fabricated and reasonable agreement among the circuit analysis, simulation response, and measured result is obtained under normal incidence.