Analysis of the Transmission Performance Limits for a Multilayer Transmitarray Unit Cell

This communication presents a theoretical study that establishes the performance limits for a multilayer transmitarray unit cell. This is the first study to be applicable to unit cells in which the conducting resonators, on the different layers, are shaped differently. A theoretical calculation is derived at the beginning. The theoretical calculations predict that, for an S
₂₁
amplitude of −1 dB, unit cells having two and three conducting layers provide a phase shifting range of 170° and 360°, respectively. In addition, for a given phase shifting range of S
₂₁
, a new methodology for analyzing the maximum S
₂₁
amplitude, based on different substrates, is proposed. For the first time, we prove that it is efficient to attain the maximum S
₂₁
amplitudes by employing a smaller substrate permittivity or a quarter-of-wavelength substrate electrical thickness. Finally, the theoretical calculations have been validated through computer simulation.