Two-dimensional beam steering using an electrically tunable impedance surface

Abstract

By covering a metal ground plane with a periodic surface texture, we can alter its electromagnetic properties. The impedance of this metasurface can be modeled as a parallel resonant circuit, with sheet inductance L, and sheet capacitance C. The reflection phase varies with frequency from + to , and crosses through 0 at the LC resonance frequency, where the surface behaves as an artificial magnetic conductor. By incorporating varactor diodes into the texture, we have built a tunable impedance surface, in which an applied bias voltage controls the resonance frequency, and the reflection phase. We can program the surface to create a tunable phase gradient, which can electronically steer a reflected beam over + 40 in two dimensions, for both polarizations. We have also found that this type of resonant surface texture can provide greater bandwidth than conventional reflectarray structures. This new electronically steerable reflector offers a low-cost alternative to a conventional phased array.

A Varactor-Tunable High Impedance Surface for Active Metamaterial Absorber

“…The resonance frequency of a mushroom-type HIS will be tuned by adjusting the values of its effective circuit parameters. A relevant electrically tunable HIS is presented in [4,5], in which the adjacent patches are connected by varactors, and the bias network for the loaded varactors is located on a separate circuit layer on the back of the ground plane.…”

“…In [4,5], each metal patch in the periodic surface texture is connected to all of the adjacent patches by reverse biased varactors. To simplify the structure, we only connect the patch with two of the adjacent ones.…”

“…A well-established method for tuning HIS is incorporating electronically tunable components into its unit cells. A limited number of electronically tunable HISs have been designed using solid-state varactor diodes [4][5][6][7][8][9]. For biasing the varactor diodes, the tunable HIS requires a separate circuitry.…”

Synthesis of Steered Flat-top Beam Pattern Using Evolutionary Algorithm

“…The concentric circular ring array antenna (CCRA) is very efficient to steer the beam patterns, which enables to increase the capacity in directional communication systems. Various techniques have been reported in the literature as given below [3][4][5][6][7][8]. Azevedo proposed a technique to generate shaped beam patterns from a linear array antenna through the control of nonuniformly samples of the array factor, both in amplitude and phase based on Fast Fourier Transform (FFT) [3].…”

“…Reyna et al described the design procedure of steerable concentric rings array for low side lobe level using Genetic Algorithm [6]. A new steerable reflector which can electronically steer a reflected beam over +/ − 40 o in two dimensions for both polarizations have been proposed and implemented [7] Figure 1: Geometry of concentric ring array Antenna have been carried out using Differential Evolution Algorithm, which improves the dynamic range ratio by eliminating weekly excited array elements [8].…”