Characteristic mode analysis of resistor-loaded frequency selective surfaces: Theoretical research and experimental verification

In this paper, the modal behaviors and the frequency properties of resistor-loaded frequency selective surfaces have been systematically studied based on the periodic moment method and characteristic mode analysis. Through the observation of the phase curves of the reflection coefficients, we found that as the resistance value increases, the resonant frequency gradually moves toward higher frequencies. By calculating and analyzing the modal currents and the modal reflection coefficients of each mode, we know that the phenomenon is caused by higher-order modes. In order to reduce the influence of higher-order modes on the resonant frequency, a method of using more load resistors is proposed. To verify the proposed method, an absorber with high absorptivity is designed and measured. The measurement shows that the absorptivity of the designed absorber is more than -18 dB in the range of 1.92- 3.99 GHz. The experiment proves that the proposed loading method can be used to flexibly regularize the equivalent impedance of the lossy frequency selective surface without worrying about the negative effects of load resistors in the design of a circuit analog absorber.

Automated summary

In this paper, the modal behaviors and frequency properties of resistor-loaded frequency selective surfaces were studied systematically. It was observed that as the resistance value increases, the resonant frequency moves towards higher frequencies, primarily due to higher-order modes. A method of using more load resistors to reduce the impact of higher-order modes on the resonant frequency was proposed and validated through the design and measurement of an absorber with high absorptivity in specific frequency ranges. The experiment demonstrated that the proposed loading method can effectively regulate the equivalent impedance of lossy frequency selective surfaces without negative effects on circuit analog absorber design.