Tunable Electromagnetic Band Gap Research Articles

Characterization of tunable electromagnetic band gap material with disordered cavity resonator for X band imaging applications by resistive devices

Electromagnetic band gap (EBG) integrated monopole antenna is investigated in deformed cavity resonator in this study. The operation frequency is chosen as X band frequency regime and designs are completed for this frequency. Firstly, a square grounded monopole antenna is designed and analytically examined, then EBG grounded monopole is designed and tested. After that operation, an 8 cm × 8 cm × 8 cm cubic cavity resonator designed and antennas are examined in it. Moreover, a cuboid deformation is added in one corner of metallic cavity resonator to perturb rectangular eigenmodes. Also, tunability of this structure is tested by various resistive lumped elements, and according to results, resonance shifting and magnitude changes are obtained. This suggested structure is also an adjustable impedance surface and can be used in sensing, detection and microwave imaging applications.

Tunable Double-Layer EBG Structures and Application to Antenna Isolation

A novel electronically tunable two-layer slot-patch one-dimensional electromagnetic band-gap (EBG) structure with significantly simplified biasing network is presented. The proposed structure consists of apertures (slots or slits) etched off a metallic ground, and a varactor-loaded patch printed on a thin dielectric substrate, placed on top of each aperture. The apertures are initially designed using microstrip line excitation and a stop-band is produced in the ${\text{S}_{{21}}}$ response. Tuning of the stop-band is achieved by changing the voltage applied to the varactors which are electrically isolated from the metallic ground, resulting in a simple biasing configuration. As a practical application, the proposed tunable EBG structures are employed in the common ground plane of two closely spaced printed monopole antennas, significantly reducing the mutual coupling between them. Simulation results and measurements of fabricated prototypes are presented.

Electromagnetic band-gap structure design using the auxetic unit-structure for easily controllable tunability

Tunable electromagnetic band-gap structures for matching an intended band-gap range have more potential for various applications than ordinary electromagnetic band-gap structures with a fixed or non-linearly variable band-gap range. However, there has not been much progress on the study of the appropriate shape of the structure. To obtain a controllable and tunable electromagnetic band-gap, we propose a new design concept employing a unit-structure with a negative Poisson's ratio close to −1 to realize an approximately linear band-gap shift according to the variation of the shape of the structure. We used a structural optimization procedure based on the phase field method to obtain the design of the unit-structure. We investigated the relation between the auxetic unit-structure deformation and the change in the band-gap range through numerical simulations and also evaluated the possibility to realize the design experimentally in the radio frequency range.

Reconfigurable wideband to narrowband antenna using tunable EBG structure

In this paper, frequency reconfigurable electromagnetic band gap (EBG) structure that integrates with a wideband antenna is proposed. The EBG structure consists of a circular patch shorted to the ground plane and a secondary circular patch connected to the circular patch. Switches are positioned between the via and the ground plane and by controlling the state of the switch, the band-stop operation of the EBG can be activated or deactivated. In order to control the single and dual band-stop operation, another switch is place between the circular patch and the secondary circular patch. The EBG structure is then placed underneath the feed line of a wideband antenna. The antenna is capable of reconfiguring to three different frequency bands. The proposed antenna has the potential to provide useful features for the wireless communication applications.

A low profile polarization reconfigurable dipole antenna using tunable electromagnetic band‐gap surface

ABSTRACTIn this article, we present a low profile polarization reconfigurable dipole antenna using a tunable electromagnetic band‐gap (EBG) structure as ground plane. The EBG structure can be dynamically modulated by tuning the loaded PIN diodes through bias voltage circuit. The EBG‐based antenna is fabricated and measured. Experimental results show that the tunable EBG structure can make the dipole antenna work at four states. For the state 1 and state 2, the emitted waves with left‐hand and right‐hand circular polarization are produced at 4.6 GHz, and the axial ratio is 1.2 and 0.3 dB, respectively. For the state 3 and state 4, the dipole antenna radiates the linearly polarized waves with the gains of about 6 dB at 4.6 and 4.25 GHz, respectively. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1281–285, 2014

Tunable electromagnetic band gap-embedded multimode resonators for ultra-wideband dual band, lower-ultra-wideband and upper-ultra-wideband applications

Three ultra-wideband (UWB) microstrip band-pass filters (BPFs) are proposed using tunable electromagnetic band gap (EBG)-embedded multiple-mode resonator (MMR) and fork resonator. In the first case, a compact dual-band BPF is implemented using a cascade of a multimodal fork resonator with tunable EBG. The fork resonator forms the basic structure yielding multiple band-pass realisations and the EBG selects the desired bands. This yields a compact dual-band BPF with sharp cut-off characteristics, wide bandwidth and low insertion loss. In the second case, a lower UWB filter is proposed by tuning an EBG-embedded MMR with parallel coupled microstrip line. Open circuited coupling stubs are introduced within the EBG structure to suppress higher order pass bands. In the third case, an upper UWB BPF is proposed in a similar manner as the lower UWB filter. However, the EBG-embedded MMR structure and the coupling technique are different. It is shown that the measured results are well matched to the predicted ones in terms of insertion/return losses over the plotted frequency range of 0.1–20.0 GHz. All simulations were performed with advanced design system (ADS) momentum (2.5D method of moments).

Effects of a Coplanar Waveguide Biasing Network Built Into the Ground Plane on the Dispersion Characteristics of a Tunable Unit Cell With an Elliptical Patch and Multiple Vias

The effect of the biasing network (BN), formed by coplanar transmission lines (CPWs) built into the ground plane itself, on the dispersion characteristics of a tunable unit cell (UC) is investigated. The UC consists of an elliptical patch and multiple vias placed inside a parallel plate waveguide. One of the vias attached to a patch positioned on the top surface of a dielectric substrate connects the patch to the ground plane. Another via, symmetrically positioned with respect to the patch center, can be connected to the same ground plane or let to float depending on the state of a diode positioned at its base. The effect of the different components of the BN is analyzed step by step. For each intermediate configuration, the corresponding dispersion diagram (DD) is computed, allowing extraction of fundamental information on the influence of each part of the CPW circuit on the band-gap characteristics. The orientation of the BN is also discussed. The presented results can guide the dispersion engineering process when a tunable electromagnetic band-gap (EBG) structure is designed for a specific guided-wave application.

Active Switching Devices in a Tunable EBG Structure: Placement Strategies and Modelling

Different placement strategies for Field-Effect-Transistor (FET) active switching devices in an electromagnetic band gap (EBG) periodic structure are investigated. Two possible placements for the switches are considered: (a) switches on top of a substrate and (b) switches at the ground-plane level. Their advantages and drawbacks are analyzed and discussed in relation to fabrication, extension to 2-D and ground plane design. The transmission results and band gaps of the EBG structure are presented for both switch placements. When determining the transmission of the structure, the FET switches are modeled in two different ways, first as an ideal conductor and then using a more accurate model consisting of embedded scattering parameters. Significant differences have been observed between the results predicted using simple and accurate models. Experimental characterization of the switch reveals technological issues related to their biasing.

Realization and modulation of negative permeability using an array of hexaferrite rods

The realization of negative permeability of an array of ferrite rods and the influencing factors are presented. The negative permeability is realized around the ferromagnetic resonance frequency of ferrite, and a tunable electromagnetic band gap is observed in the array of ferrite rods. The electromagnetic property of the array of ferrite rods is dominated by the unit's characteristics, including the dimension of the rods, but is insensitive to the structure parameters, such as spacing distance and duty ratio, which indicates that the array is a metamaterial, not a photonic crystal. Metamaterials with multi-band gaps are made using an array with different ferrite rods.

Tunable electromagnetic bandgap performance of coplanar waveguides periodically loaded by ferroelectric varactors

AbstractTo achieve tunable electromagnetic bandgap (EBG) performance, ferroelectric varactors are considered, in LC circuits, for periodically loading coplanar waveguides (CPWs). Asymmetric or symmetric tuning of the bandgap width may be achieved by changing the capacitance of the varactors in the LC circuits. To validate this concept, tunable EBG arrays based on silicon substrate CPWs, including thin film SrTiO3 (STO) varactors, are fabricated and tested experimentally. The EBGs are designed so that the first band gap starts between 20 and 30 GHz. Up to 10% tuning is achieved, under 20‐V DC applied bias, in the EBG structures. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 81–86, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11134