Effect of Losses on Tunable High Impedance Surface

Reconfigurable metasurfaces for multi-functional antennas can be designed by using lumped electronic elements in each unit cell. However, those additional components may not have negligible losses and it may lead to substantial absorption by the metasurface. In this paper, the influence on the performances of a High Impedance Surface (HIS) is investigated after the introduction of lumped elements with a significant resistive part, between each unit cell. The ratio between the HIS unloaded quality factor Q
0
and the unit cell electrical length is proposed as a criterion to compare different unit cell designs, since it takes into account losses inside the structures. The relationship between the quality factor and the usual definition of HIS bandwidth is also investigated.