Çiğdem Seçkin Gürel

New computation of the resonant frequency of a tunable equilateral triangular microstrip patch

A new dynamic permittivity expression is formulated to be used in the cavity analysis to determine the resonant frequency of an equilateral triangular microstrip patch. The proper sidelength extension expressions are given for low and high substrate permittivity cases. Better accuracy with respect to the moment method and other previous models is obtained for various structural parameters and operational modes. The proposed computation is also extended for the analysis of the two-layer structure in order to determine the air-gap tuning effect on the resonant frequency.

Characteristics of a circular patch microstrip antenna on uniaxially anisotropic substrate

Resonant characteristics of a circular patch microstrip antenna on the uniaxially anisotropic substrate are determined via spectral domain analysis. Greens functions of the structure in Hankel transform domain are determined by using Hertz vector formulation. The variations in the resonant characteristics depending on the replacement of the isotropic substrate with the uniaxially anisotropic one are analyzed for different permittivity tensor element cases. The results of the study indicate that resonant frequency and bandwidth characteristics of the antenna can be considerably changed due to proper selection of substrate anisotropy ratio and other structural parameters. Depending on the arrived results, operational performance of the antenna will be improved in future studies.

Resonant frequency of an air gap tuned circular disc microstrip antenna

In this study, the formulation and the computation of the resonant frequency of an air gap tuned circular disc microstrip antenna are simplified, with improved accuracy, by using a new and very simple effective permittivity expression which is valid for thin and thick gaps. Very good agreement between the theoretical and the experimental resonant frequency values is obtained for the various structural parameters and operational modes.

INTERACTION OF ELECTROMAGNETIC WAVE AND PLASMA SLAB WITH PARTIALLY LINEAR AND SINUSOIDAL ELECTRON DENSITY PROFILE

Interaction of an electromagnetic wave and an inhomoge- neous plasma slab with electron distribution in the form of partially linear and sinusoidal proflles is analysed to determine new re∞ection, absorbtion and transmission characteristics. Broadband and tunable absorbtion performance of the plasma layer accompanied with narrow- band re∞ection characteristic is presented as the function of electron density proflle parameters and external magnetic fleld excitation. Ac- cording to the resulting performance characteristics, proposed plasma layer is found to be useful as a new absorbing layer for shielding and stealth applications.

Analysis of Annular Ring Microstrip Patch on Uniaxial Medium via Hankel Transform Domain Immittance Approach

In this study, resonant frequency of annular-ring mi- crostrip patch on uniaxial medium is determined using equivalent mod- els of the structure obtained in Hankel Transform Domain depending on TE and TM mode decomposition. For the simpliflcation of the tensor form formulations, equivalent matrix operators are deflned in cylindrical coordinates instead of the difierential ones. Then, eigen- value problem is solved by the application of the moment method and obtained resonant frequency characteristics are compared with that of the isotropic case for difierent anisotropy ratio values and structural parameters. Equivalent circuit models for the structure having mul- tilayered substrates and superstrates are given in order to be used in the following studies on uniaxially anisotropic circular type microstrip patches.

Bandwidth widening in an annular ring microstrip antennas with superstrate

A theoretical and numerical analysis of an annular ring microstrip antennas with superstrate is performed in order to obtain a wider bandwidth operation. At the same time the complex resonant frequency of the structure is determined. The study is performed by using a full wave analysis and Galerkins moment method in Hankel transform domain by taking surface wave contributions into account. The possibility of achieving larger bandwidth operation with TM/sub 11/ mode which originally shows narrow bandwidth characteristics in single layer annular ring antenna is investigated. Numerical results for different antenna parameters are given. The results indicate that the resonant frequency decreases with increasing superstrate thickness and the bandwidth increases for increasing superstrate dielectric constant values.

Resonance in Microstrip Ring Resonator with Uniaxially Anisotropic Substrate and Superstrate Layers

Resonance in annular-ring microstrip resonator with uniaxially anisotropic substrate and superstrate layers is analysed in Hankel Transform domain using immitance approach. Resonant frequency shift due to uniaxial anisotropy is firstly investigated for different anisotropy ratio values of substrate and superstrate layers with respect to each other. The results obtained indicate that resonant frequency of anisotropic resonator has higher or lower values as compared to isotropic case according to the adjustment of the layer anisotropies. Then, the effect of inclusion of air gap layer inserted between substrate and ground plane on the resonance characteristics is also investigated for different superstrate anisotropies. The overall results provide helpful design criterias for the more efficient operation of microstrip ring for communications and integrated circuit applications.

Accurate Resonant Frequency Computation of Multisegment Rectangular Dielectric Resonator Antennas

In this study, multi-segment dielectric resonator antenna (MSDRA) is analyzed. A new formulation depending on the Weighted Average Model (WAM) is proposed for the determination of resonant frequency which is called as Modified Weighted Average Model (MWAM). According to the comparison of the results with experimental values and the results of the previous studies and simulation results it is shown that considerable improvement is obtained using this new formulation providing very small percentage errors for almost all cases.

Modified Cavity Model to Determine Resonant Frequency of Tunable Microstrip Ring Antenna

ABSTRACT In order to compute the resonant frequency of an air-gap tuned annular-ring microstrip antenna without the accuracy being affected from the air gap width, the cavity model is modified by using a new dynamic permittivity and inner/outer radii extension expressions. A close agreement is obtained between the theoretical and the experimental resonant frequency results for fundamental and higher order modes and for different gap widths.

A new narrowband multilayer DWDM optical filter in the order of defected Fibonacci sequence

The self-similar narrow stop-bands in the reflectivity spectrum of the structures in the order of generalized Fibonacci sequence are utilized in this study. A multilayer structure in the order of generalized Fibonacci sequence is defected by a proper layer to get narrow stop-bands identical to channels of dense wavelength division multiplexing (DWDM) filter with ITU-T standard (100 GHz grid). The index profile of the defected structure is apodized and index-matched to eliminate the sidelobes between the stop-bands. After these modifications, a thin, new DWDM filter is designed having significantly suppressed sidelobes.