High performance micromachined MM-wave FSS

A new design approach is described which enables the efficiency of rapid-roll off multilayer FSS beamsplitters to be significantly increased by eliminating the dielectric absorption loss. This is achieved by producing free standing slot element arrays which allows the lossy interlayer material, that provides the physical separation between the filters, to be completely removed (i.e. tanδ=0) whilst maintaining the mechanical integrity of the device. At very high frequencies this technique offers an attractive solution because the resonant elements may be formed using silicon micromachining techniques. Eliminating the dielectric material in the design of high performance in the design of high performance bandpass filters at MM wave frequencies is discussed. The performance has been quantified by applying both measurement and simulation techniques to characterise the frequency response of a double layer slot dipole array FSS, where the screens are separated by an air gap