Bartol Research Institute, University of Delaware, Newark, Delaware 19716, USA(Dated: May 8, 2008)We identify diﬀerent types of the photonic band gaps (PBGs) of two dimensional magnetic pho-tonic crystals (MPCs) consisting of arrays of magnetic cylinders and study the diﬀerent tunability(by an external static magnetic ﬁeld) of these PBGs One type of the band gaps comes from in-ﬁnitely degenerate ﬂat bands and is closely related to those in the study of plasmonics In addition,such PBGs are magnetically tunable and robust against position disorder We calcualte the trans-mission of the PBG’s and found excellent agreement with the results of the photonic band structurecalculation Positional disorder of the lattice structure aﬀects the diﬀerent types of PBGs diﬀerently

Formation of robust and completely tunable resonant photonic band gaps

In this paper, we present experimental verification of the sensitivity improvement of evanescent-field probes using single-negative (SNG) metamaterials. Artificial magnetic materials are designed and fabricated to realize a ?-negative SNG material. The response of an electrically small probe to an electrically small target is investigated numerically and experimentally. The deviation in the phase of reflection coefficient due to the target is measured. When an SNG layer is employed, phase shift due to the presence of a target is improved nine times compared to a probe without an SNG layer.

Experimental and Numerical Study of Sensitivity Improvement in Near-Field Probes Using Single-Negative Media

In this article, a single-stage power amplifier and two-way Doherty amplifier are linearized by the technique that uses second harmonics and fourth-order nonlinear signals. Measurements of the linearization effects on the third- and fifth-order intermodulation products have been carried out. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:425–430, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27294

Linearization of power amplifiers by second harmonics and fourth-order nonlinear signals

Transmission characteristics of two-dimensional magnetized magnetic photonic crystals (MPCs) have been studied by electromagnetic simulation and experiments in microwave frequencies. MPCs with square and hexagonal lattices are made of ferrites, and their transmission coefficients are measured in the X waveband with an applied static magnetic field. For the lattices, a stop-band and a band shift with the applied static magnetic field are observed. The experimental results are in good agreement with those of electromagnetic simulations when magnetic anisotropy of ferrites is represented by a tensor but deviate from the simulation results when the anisotropy is modelled by an effective permeability of TMz mode.

Transmission characteristics of two-dimensional magnetized magnetic photonic crystals

A sandwich vehicle structure may allow for confined propagation of electromagnetic radiation within the sandwich vehicle structure. The sandwich vehicle structure may include at least one upper conducting plate, at least one lower conducting plate, and a core extending between the upper and lower conducting plates. The core may comprise a core medium, and a plurality of spaced apart core members embedded in the core medium and extending between the upper and lower conducting plates. The core medium and the core members may allow for the propagation of electromagnetic radiation within the core.

Sandwich vehicle structure having integrated electromagnetic radiation pathways

We report the use of low dielectric constant materials to form two-dimensional microwave band-gap structures for achieving high gap-to-midgap ratio. The variable parameters chosen are the lattice spacing and the geometric structure. The selected geometries are square and triangular and the materials chosen are PTFE (e = 2.1), PVC (e = 2.38) and glass (e = 5.5). Using the plane-wave expansion method, proper lattice spacing is selected for each structure and material. The observed experimental results are analyzed with the help of the theoretical prediction

Two-dimensional microwave band-gap structures of different dielectric materials

We report the theoretical work on the photonic band gap structures suitable for microwave frequency region formed by magnetic materials ( e = 9.87 and μ = 2.17 ) using plane wave expansion method. The structures under analysis are two-dimensional square and triangular lattices. The calculated band gap between 10 and 20 GHz region is anlaysed for the effect due to lattice spacing and the property of the material. The results are also compared with that of pure dielectric case. Obtained results indicate that both impedance and effective refractive index are responsible for the gap width and mid-gap frequency.

Numerical study of the effect of permeability on square and triangular microwave band gap structures

Two dimensional microwave band gap structures have been constructed using lossy cylindrical glass samples (\(\varepsilon^\prime = 5.5\) and \(\varepsilon " = 0.1\)). The power transmission spectra observed between 10 and 20 GHz for both square and triangular structures with three different lattice spacing (2.5, 1.4 and 0.9 cm) are explained in terms of the lattice spacing, filling fraction and loss tangent. The experimental results and the theoretical values agree well for the structures having higher filling fraction. Also, the values predicted from the scaling procedure agree well with the experimental values. The appearance of acceptor modes due to the introduction of defects in these structures is also reported.

Microwave propagation in two dimensional structures using lossy cylindrical glass rods

This paper presents the investigation on the propagation of microwaves through the square lattice structure constructed by two different materials, glass (ϵ r = 5.5) and poly vinyl chloride (PVC) (ϵ r = 2.38). We report the transmission spectra of these structures that were recorded between 7 and 20 GHz. It is observed that the glass structure of lattice constant 1.4 cm gave a band gap centered around 17 GHz with a gap width of 3.5 GHz and attenuation of 30 dB. With PVC rods, the spectra were recorded for two different lattice constants 1.4 cm and 1.1 cm. The structure of 1.4 cm shows a band gap centered at 16.8 GHz with a gap width of 1.48 GHz where as the structure of 1.1 cm lattice constant shows a band gap centered at 11.17 GHz with a gap width of 2.67 GHz. The attenuation in both cases is around 25 dB. The analysis shows that the gap width is low for structures made of PVC rods when compared to structure made of glass as expected because of the low dielectric constant of PVC. It is also observed that...

Microwave Propagation in a Square Lattice Using Different Dielectric Materials for Device Applications

The use of microwave band gap structures for the non-destructive evaluation of material property is being probed in this paper. As a flrst step, we studied numerically, the appearance of a point defect mode within the band gap of a microwave band gap structure for the use as a tool to evaluate the dielectric constant of the material at the defect site. The simulations were carried out using the FEMLAB software. In a pure 10£10 square lattice constructed with a material of dielectric constant (") 5.5 (in the form of a right circular cylinder), a point defect is created by replacing one of the rods with a geometrically similar but with difierent dielectric constant material. The appearance of the defect mode is governed by the refractive index contrast (deflned as the ratio between the refractive index of the material at the defect site (nd) and the material of the lattice (nl). In this case, the refractive index contrast (nd=nl) was found to be between 0.85 and 1.28. Simulations were also done with the lattice material of dielectric constant 10 and the defect mode appeared for 1:18 < nd=nl < 0:84. For the contrast less than 1, defect creates the fundamental mode similar to TE01 mode whereas for the contrast greater than 1, next higher mode similar to TE11 appears. Once a defect mode appears, it moves towards lower frequency as the dielectric constant of the defect site is increased. In this paper, we propose to evaluate the dielectric constant of a material using the above procedure. This paper also proposes the construction of a novel frequency selector switch that has two line defects in a 10£20 square lattice structure constructed with material of dielectric constant 10.

https://www.piers.org/piersonline/pdf/Vol4No6Page631to634.pdf

E. D. V. Nagesh

Papers

Two-dimensional microwave band-gap structures of different dielectric materials

Numerical study of the effect of permeability on square and triangular microwave band gap structures

Microwave propagation in two dimensional structures using lossy cylindrical glass rods

Microwave Propagation in a Square Lattice Using Different Dielectric Materials for Device Applications

Application of Defect Induced Microwave Band Gap Structure for Non-destructive Evaluation and the Construction of a Frequency Selector Switch