Minimal Size Fss for Long Wavelength Operation

The properties of small finite size FSS for use particularly at long wavelengths are summarised. The intended use is the modification of the EM architecture of buildings at mobile radio frequencies. Introduction: At microwave and millimetre wave frequencies the physical sizes of Frequency Selective arrays are, in virtually all practical applications, large enough for the structures to be adequately modelled in design work as if they are electrically infinite in extent. Nevertheless, studies of finite sized FSS have been made, and reported in the open literature. References 1 and 2 are examples. It emerged from that work that the currents induced in the array elements by incident electromagnetic waves are not uniform – they are often highly dependent on the location of the element in the array, with the greatest non-uniformity being in the edge region [3]. With the increasing interest in the application of FSS at the frequency bands used for mobile communications, and in particular their application to buildings, in effect to modify their Electromagnetic Architecture, the implications of the much longer operating wavelengths for the design of practical frequency selective structures are significant. The arrays become correspondingly much larger – scaling in proportion to typical operating bands implies large increases in their areas, by a factor of almost 1000 if a design for near 12 GHz were scaled to 400 MHz, for example. One question that immediately arises is how many array elements are required to generate useful frequency selectivity? The smaller the number, presumably the lower are the costs of production, particularly if active devices were to be included in the structure. In mobile communications and wireless local area networks, a comparatively small reduction in signal interference can give very significant