Bandwidth variations in conformal infrared frequency selective surfaces

Infrared Frequency Selective Surfaces (FSS) have been demonstrated to control the spectral emissivity and reflectivity of a surface in the 3-6 mum band. These structures were designed using rigid substrates and with radiation only at normal incidence. Previous research has demonstrated conformal FSS transmission filters in the mid-infrared band. This paper will show the design and testing of an infrared FSS for control of spectral emissivity and reflectivity, and operating in the 3-6 mum band. The FSS performance will be demonstrated at angles of incidence from 0 to 30 degrees. Both square loop and loaded cross elements will be considered. The bandwidth of the loaded cross is shown to vary significantly with variation in angle of incidence while the bandwidth of the square loop is more stable.