Abstract: A radiation absorber comprising multiple layers has a conducting base layer, and at least first and second further layers, each separated by a dielectric material, the first and second layers having patches thereon of highly conducting material, and defining resonant cavities in cooperation with the dielectric material, wherein the resonant cavities formed on adjacent layers differ in frequency. Characteristics of the patch, such as size or shape may vary on each layer to provide different resonant frequencies, and/or dielectric or magnetic properties of the dielectric material, and/or separation distance of the patches may be varied. In some embodiments, complex dielectrics may have their loss factors adapted to tune a resonant frequency, or to adapt its resonant bandwidth.

Abstract: Some embodiments are directed to an antenna for use in interrogating RFID tags in close proximity thereto. The antenna can include an active element configured to resonate at or close to a frequency required to read an RFID tag, the active element comprising a feed point; and a plurality of passive elements, each passive element being configured to resonate at or around a frequency corresponding to said frequency, the passive elements being arranged around the active element such that the passive elements electromagnetically couple to the active element when the active element is driven by a signal supplied through the feed point.

Abstract: A radiation absorber comprising multiple layers has a conducting base layer, and at least first and second further layers, each separated by a dielectric material, the first and second layers having patches thereon of highly conducting material, and defining resonant cavities in cooperation with the dielectric material, wherein the resonant cavities formed on adjacent layers differ in frequency. Characteristics of the patch, such as size or shape may vary on each layer to provide different resonant frequencies, and/or dielectric or magnetic properties of the dielectric material, and/or separation distance of the patches may be varied. In some embodiments, complex dielectrics may have their loss factors adapted to tune a resonant frequency, or to adapt its resonant bandwidth.