Cylindrical-water-resonator-based ultra-broadband microwave absorber

In this study, a cylindrical-water-resonator-based absorber with an ultra-broad operating band at microwave wavelengths is demonstrated theoretically and experimentally. By utilizing the dielectric resonator mode, spoof surface plasmon polariton mode, and grating mode of the cylindrical water resonator, the proposed absorber exhibits an absorptivity higher than 90% over almost the entire ultra-broad operating band from 5.58 to 24.21 GHz, with a relative bandwidth as high as 125%. The angular tolerance and thermal stability of the proposed absorber are simulated, and the results indicate that the absorber performs well in a wide range of angles of incidence and exhibits a weak dependence on the water temperature. The low cost, ultra-broad operating band, good wide-angle characteristics, and thermal stability make the absorber promising for applications in antenna measurement, stealth technology, and energy harvesting.