Design and characterization of square patch Salisbury screen microwave absorber

The work presents an inventive, simple and implementable design approach to enhance the bandwidth of conventional Salisbury Screen Microwave Absorber (SSMA). Theoretically, the maximum fractional bandwidth of SSMA for FR4 substrate with an optimum sheet resistivity of 308 Ω/sq for –10 dB reflection is nearly 42.1%. In comparison, the bandwidth for square patch based SSMA is 59.7% with the same thickness. The design comprises square patches of SSMA placed periodically on a metal sheet. The square patches consist of an FR4 substrate and a 200 Ω/sq resistive sheet. A single reflection null is observed in the SSMA due to λ/4 resonance whereas in the proposed absorber an additional resonant mode is introduced due to coupling between the nearby patches. The simultaneous overlapping of the λ/4 mode and the additional coupling mode results in bandwidth extension. The close agreement between the simulation and measurement data is observed.