Modeling and Design of Electronically Tunable Reflectarrays

Abstract

The reflectarray has significant promise in applications requiring high-gain, low-profile reflectors. Recent advances in tuning technology have raised the possibility of realizing electronically tunable reflectarrays, which can dynamically adjust their radiation patterns. This paper presents an electronically tunable reflectarray based on elements tuned using varactor diodes. Modeling approaches based on an equivalent circuit representation and computational electromagnetics simulations are presented. Both techniques accurately predict the scattering characteristics of the unit cell as compared to experimental measurements. The development of a unit cell with over 320 of phase agility at 5.5 GHz is discussed. Finally, a 70-element electronically tunable reflectarray prototype operating at 5.8 GHz is presented. Radiation pattern measurements with the reflectarray demonstrate its dynamic beam-forming characteristics. Measurements of the gain of the reflectarray correlate well with theoretical expectations.

Equivalent Electrical Circuit for Designing Mems-Controlled Reflectarray Phase Shifters

“…1, the transverse electromagnetic mode (TEM) is the only one propagating mode within the operating The phase shift applied to the TEM mode when reflecting from the cell is assumed to be identical to that experienced by a plane wave electric field incident on a given cell [7]. The estimation of this phase shift or equivalently the phase of the reflection coefficient Γ through a simple equivalent circuit model is now presented.…”

“…Recently, an equivalent circuit [7] based on the transmission line model is presented to analyze the scattering behavior of an electronically tunable varactor-based unit cell; however this model cannot be used as a dynamic design tool as the number of command elements and their position is fixed.…”

Contributions to the Modeling and Design of Reconfigurable Reflecting Cells Embedding Discrete Control Elements

“…This RWG can be used to characterize the reflection phase of a cell symmetrical around both its -and -axes, in the periodic environment of Fig. 2 and for an incidence , according to (9) [18] as follows:…”

“…The number of elements placed in the RWG cross section is not necessarily 1. According to image theory, there can be any number of half-elements placed in the RWG, so for an array of lattice spacing with (10) Observation of (9) shows that the RWG characterization of a cell is only possible for a given incidence angle at each frequency, which is determined by the choice of .…”

“…Indeed, in addition to the known advantages of reflectarrays over parabolic reflectors [1], dynamically controllable reflecting cells would allow electronic reconfigurability. In this context, controllable reflecting cells employing different technologies for microwave reconfigurability have recently been investigated, using ferroelectric thin films [4], liquid crystals [5], photonically controlled semiconductors [6], or varactor diodes [7]- [9]. In addition, there is a particular interest in developing cells based on microelectromechanical system (MEMS) technology [10]- [15], which allows a significant reduction of the losses, intermodulation effects, and dc power consumption, while extending the high-frequency limit of operation for such devices.…”