Researchers at Queen's University Belfast's Centre for Wireless Innovation (CWI) have combined expertise in on-body wireless sensors and frequency selective surfaces to solve a problem limiting the RF performance of medical sensors.
Conventional frequency selective surfaces (FSSs) reflect or transmit microwave energy at particular resonant frequencies. However, there is a newer class of periodic structures, thin resistively loaded FSS absorbers, which absorb most of the incident power. This class of microwave absorber has the potential to significantly enhance the RF performance of all existing and future physical layer communication systems used in environments, hostile to propagation. Thin resistivity loaded FSS absorbers have planar, thin and lightweight metal-backed patterned screens, making them particularly suitable for suppressing wave refl ections from metal objects such as wind turbines as well as land, air or space-based vehicles.
Normally, FSS arrays are simulated and measured in the ‘far field’ of the excitation antenna. This means that the separation distance is sufficiently large for the periodic absorber surface to be excited by plane waves. For all conventional RF applications this is a reasonable assumption, for example a radar system is generally positioned remotely and far from the structure that it interrogates. However, for healthcare monitoring applications, near field solutions are required as there is close contact between the absorber surface and excitation antenna.