On the Improvement of Angular Stability of the 2nd-Order Miniaturized FSS Structure

To improve the angular stability of 2nd-order bandpass miniaturized frequency selective surface (MFSS), consisting of metal patch and wire frame layers and supporting dielectrics, the authors proposed a new arrangement of patch and wire frame layers. The appearance of the strong captive coupling between the edges of the patch and wire frame stabilizes the resonating frequency via different incident directions. It is demonstrated that the proposed MFSS arrangement works well with the classic outer dielectric bonding technique, which stabilizes the flat-top filtering properties of the 2nd-order MFSS via different incident directions, but does not help much in restricting resonating frequency shifts. Therefore, the proposed modification can be a very effective method of designing 2nd-order bandpass MFSS with angular stability requirements.