Investigating finite FSS in the near field

In conventional frequency selective structures (FSS) applications it is standard to assume the array to be infinite and uniform. For application to building structures it is necessary to truncate the extent of FSS to a large extent. A 3x3 square slot loop (band pass) FSS has been investigated in terms of its near field performance. Reported measurements demonstrated simple electrically small, finite, FSS are capable of allowing signal access for TETRA at 400MHz while providing at least10 dB isolation to mobile and wireless services. This gives potential to enhance frequency reuse leading to efficient management of the frequency spectrum. Previous measurements were taken of transmission response in a plane wave chamber. In this paper, the near field is simulated and probed to establish the effect on the uniformity of individual element excitation caused by the highly finite nature of the FSS array.