Frequency-selective surfaces with dumbbell shaped elements

One possible application of band-pass frequency-selective surfaces (FSS) is the frequency-selective radome. Usually, band-pass FSS appear as metallic screens, perforated periodically with apertures. The holes in the screen, resonating at pass-band central frequency f/sub 0/, may take various forms. The required frequency f/sub 0/ is provided by the selection of aperture dimensions, and the pass bandwidth is determined by the spacing between apertures. However, unwanted passbands appear at high frequencies, multiple of frequency f/sub 0/. A shift of unwanted pass-bands into a "not dangerous" frequency region or damping of the FSS transparency in these frequency bands is a problem of practical interest. One way to solve the problem is in the rational selection of hole geometry. For example, a positive result may be expected in the case of holes with locally separated inductance and capacity (e.g., holes in the form of a dumbbell). This work presents a theoretical and experimental study of dumbbell FSS performance. Broadband measurements of transmission coefficients for different incident wave angles through a band-pass FSS with dumbbell aperture elements demonstrate positive features. For these FSS, the unwanted transmission bands may be shifted sufficiently far to a high-frequency region.