Absorbing frequency-selective-surface for the mm-wave range

We report on a millimeter-wave (mm-wave) absorber based on the frequency selective surface. It consists of a periodic array of resistive patches on a grounded dielectric layer. By varying the shape of the patches and the distance between them, the device can be tuned to absorb in a given frequency band. We designed and fabricated several devices consisting of square arrays of Nichrome circles or rings. The design was targeted to the mm-wave range, 75-110 GHz. Our measurements of the mm-wave reflection from these devices show good agreement with computer simulations. We discuss the use of our device as a microbolometer array.