Browsing by Subject "Microstrip antennas"

Now showing 1 - 15 of 15

Open Access
Analysis of cylindrically conformal antennas using closed-form Green's function representations
(IEEE, 2015-04) Kalfa, Mert; Karan, S.; Ertürk, Vakur B.
Probe-fed microstrip patch antennas and slotted sectoral waveguide array antennas embedded in cylindrically stratified media are analyzed with a hybrid Method of Moments/Green's function technique, where closed-form Green's function representations for electric and magnetic current sources are used as the kernel of the associated integral equations. Various patch and slot antennas are analyzed using the proposed method. Numerical results in the form of input impedance, S-parameters, and radiation patterns are presented and compared to the results obtained from CST Microwave Studio™ and HFSS™.
Open Access
Capacity of printed dipole arrays in the MIMO channel
(Institute of Electrical and Electronics Engineers, 2008-10) Tunc, C. A.; Aktas, D.; Ertürk, V. B.; Altintas, A.
Moments performance of printed dipole arrays in the MIMO channel is investigated using a channel model based on the Method of solution of the electric-field integral equation. Comparisons with freestanding dipoles are given in terms of channel capacity. Effects of the electrical properties (such as the dielectric thickness and permittivity) on the MIMO capacity are explored. Various dielectric-substrate configurations yielding high-capacity MIMO arrays are presented.
Open Access
Closed-form green's functions of HED, HMD, VED, and VMD for multilayer media
(IEEE, 1993-06-07) Aksun, M. İrşadi; Dural, G.
The closed-form Green's functions of the vector and scalar potentials in the spatial domain are presented for the sources of horizontal electric, magnetic, and vertical electric, magnetic dipoles embedded in a general, multilayer, planar medium. The spectral domain Green's functions in a arbitrary layer are obtained through the Green's function of the source layer by using a recursive algorithm.
Open Access
A closed‐form solution to the asymptotic part of the MOM impedance matrix and the MOM excitation vector for printed structures on planar grounded dielectric slabs
(John Wiley & Sons, Inc., 2007) Bakýr O.; Ertürk, V. B.
In the spectral domain method of moments (MoM) solution of printed structures on planar grounded dielectric slabs, the infinite double integrals which appear in the asymptotic parts of the MoM impedance matrix and the MoM excitation vector elements, have been previously transformed to one-dimensional finite integrals, which have been numerically computed using the highly specialized "International Mathematics and Statistics Library" subroutines. In this paper, these one-dimensional integrals are evaluated in closed-form, resulting in an improved efficiency and accuracy for the rigorous investigation of printed antennas and complex millimeter and microwave integrated circuits. Numerical results in the form of mutual impedance between two expansion functions and input impedance of various microstrip antennas are presented to assess the accuracy of these closed-form expressions.
Open Access
Computation of the resonant frequency of electrically thin and thick rectangular microstrip antennas with the use of fuzzy inference systems
(John Wiley & Sons, 2000) Özer, Ş.; Güney, K.; Kaplan, A.
A new method for calculating the resonant frequency of electrically thin and thick rectangular microstrip antennas, based on the fuzzy inference systems, is presented. The optimum design parameters of the fuzzy inference systems are determined by using the classical, modified, and improved tabu search algorithms. The calculated resonant frequency results are in very good agreement with the experimental results reported elsewhere.
Open Access
Design of dual-frequency probe-fed microstrip antennas with genetic optimization algorithm
(IEEE, 2003) Ozgun, O.; Mutlu, S.; Aksun, M. I.; Alatan, L.
Dual-frequency operation of antennas has become a necessity for many applications in recent wireless communication systems, such as GPS, GSM services operating at two different frequency bands, and services of PCS and IMT-2000 applications. Although there are various techniques to achieve dual-band operation from various types of microstrip antennas, there is no efficient design tool that has been incorporated with a suitable optimization algorithm. In this paper, the cavity-model based simulation tool along with the genetic optimization algorithm is presented for the design of dual-band microstrip antennas, using multiple slots in the patch or multiple shorting strips between the patch and the ground plane. Since this approach is based on the cavity model, the multiport approach is efficiently employed to analyze the effects of the slots and shorting strips on the input impedance. Then, the optimization of the positions of slots and shorting strips is performed via a genetic optimization algorithm, to achieve an acceptable antenna operation over the desired frequency bands. The antennas designed by this efficient design procedure were realized experimentally, and the results are compared. In addition, these results are also compared to the results obtained by the commercial electromagnetic simulation tool, the FEM-based software HFSS by ANSOFT.
Open Access
Efficient computation of surface fields excited on a dielectric-coated circular cylinder
(IEEE, 2000-10) Erturk, V. B.; Rojas, R. G.
An efficient method to evaluate the surface fields excited on an electrically large dielectric-coated circular cylinder is presented. The efficiency of the method results from the circumferentially propagating representation of the Green’s function as well as its efficient numerical evaluation along a steepest descent path. The circumferentially propagating series representation of the appropriate Green’s function is obtained from its radially propagating counterpart via Watson’s transformation and then the path of integration is deformed to the steepest descent path on which the integrand decays most rapidly. Numerical results are presented that indicate that the representations obtained here are very efficient and valid even for arbitrary small separations of the source and field points. This work is especially useful in the moment-method analysis of conformal microstrip antennas where the mutual coupling effects are important.
Open Access
Hybrid model for probe-fed rectangular microstrip antennas with shorting pins
(IEEE, 2000) Mutlu, Selma; Aksun, M. İrşadi
For a probe-fed microstrip antenna, it is quite common to employ the cavity model to find the field distribution under the patch and other electrical properties. Therefore, a multiport analysis technique based on the cavity model is usually employed to predict the input impedance of a probe-fed microstrip antenna with shorting pins. However, this approach does not provide any information about the field distribution under the patch with the shorting pins, which is usually used to calculate the radiation properties of the patch antenna. In this study, shorting pins are considered as current sources with unknown amplitudes, and the field distribution under the patch is obtained as a linear superposition of the contributions from each source via cavity model. Then, the unknown current densities over the shorting pins are determined by implementing the boundary condition of the tangential electric field on the pins. This is a hybrid approach because the field distribution is calculated from the cavity model, and the current densities over the shorting pins are obtained from the point matching of the resulting field distributions over the shorting conductors. The input impedance results found from this approach agree extremely well with those obtained from the multiport analysis, which shows that the proposed approach predicts both the input impedance and the field distribution under the patch. In addition, since the feeding probe is also made of PEC, the electric field under the patch should satisfy the boundary condition on this conductor as well. In the application of the cavity model, this is always ignored, with the assumption that the source probe is too thin to affect the field distribution under the patch significantly. In this study, the boundary condition of the electric field is implemented over the source, and its effect on the field distribution, in turn on the resonant frequency, is demonstrated.
Open Access
A Miniaturized Patch Antenna by Using a CSRR Loading Plane
(Hindawi Publishing Corporation, 2015) Ramzan, M.; Topalli, K.
This paper presents a design methodology for the implementation of a miniaturized square patch antenna and its circuit model for 5.15 GHz ISM band. The miniaturization is achieved by employing concentric complementary split ring resonator (CSRR) structures in between the patch and ground plane. The results are compared with the traditional square patch antenna in terms of area, bandwidth, and efficiency. The area is reduced with a ratio of 1/4 with respect to the traditional patch. The miniaturized square patch antenna has an efficiency, bandwidth, and reflection coefficient of 78%, 0.4%, and -16 dB, respectively. The measurement and circuit modeling results show a good agreement with the full-wave electromagnetic simulations. © 2015 Mehrab Ramzan and Kagan Topalli.
Open Access
A new effective side length expression obtained using a modified tabu search algorithm for the resonant frequency of a triangular microstrip antenna
(John Wiley & Sons, 1998) Karaboğa, D.; Güney, K.; Kaplan, A.; Akdağli, A.
A new, very simple curve-fitting expression for the effective side length is presented for the resonant frequency of triangular microstrip antennas. It is obtained using a modified tabu search algorithm, and is useful for the computer-aided design (CAD) of microstrip antennas. The theoretical resonant frequency results obtained using this new effective side length expression are in very good agreement with the experimental results available in the literature.
Open Access
On the capacity of printed planar rectangular patch antenna arrays in the MIMO channel: analysis and measurements
(IEEE, 2010) Tunc, C. A.; Olgun, U.; Ertürk, V. B.; Altintas, A.
Printed arrays of rectangular patch antennas are analyzed in terms of their MIMO performance using a full-wave channel model. These antennas are designed and manufactured in various array configurations, and their MIMO performance is measured in an indoor environment. Good agreement is achieved between the measurements and simulations performed using the full-wave channel model. Effects on the MIMO capacity of the mutual coupling and the electrical properties of the printed patches, such as the relative permittivity and thickness of the dielectric material, are explored.
Open Access
On the evaluation of spatial domain MoM matrix entries containing closed form Green's functions
(IEEE, 1997-07) Kinayman, Noyan,; Mittra, R.; Aksun, M. I.
The method of moments (MoM) is widely-used for the solution of mixed potential integral equations (MPIE) arising in the analysis of planar stratified geometries. However, the application of this technique in the spatial domain poses some difficulties since the associated spatial-domain Green's functions for these geometries are improper oscillatory integrals, known as Sommerfeld integrals, that are very computationally-intensive to evaluate. It is possible to eliminate the time-consuming task of computing these integrals by using closed form versions of the spatial domain Green's functions and the time required to evaluate the reaction integrals in the MoM matrix can be reduced considerably. Furthermore, the reaction integrals resulting from the application of the MoM can also be evaluated analytically by using piecewise linear basis and testing functions (Alatan et al., 1996). Hence, an efficient EM simulation algorithm can be developed by using the closed form Green's functions in the MoM formulation that involves no numerical integration. However, despite the time-saving realized from the analytical evaluation of the reaction integrals with the closed-form Green's functions, the need for further reducing the matrix fill-time is not obviated for many problems. Thus the objective of this paper is to present a hybrid technique for the evaluation of the MoM reaction integrals in a numerically-efficient manner that further reduces the time needed for their computation. A microstrip patch antenna is used as an example.
Open Access
Paraxial space - domain formulation for surface fields on large dielectric coated circular cylinders
(IEEE, 2001-07) Ertürk Vakur B.; Rojas, R. G.
A space-domain represention for the surface fields excited by an elementary current source was discussed. Green's function was used and an approximation was made using Fourier series (FS), where FS coefficients were calculated using numerical integration. The integrals were evaluated numerically along the real axis using a Gausian quadrature algorithm. However, the developed scheme yielded field expressions that remain valid along the paraxial region for arbitraily small and large separation between observation and source points.
Open Access
Three dimensional microfabricated broadband patch and multifunction reconfigurable antennae for 60 GHz applications
(IEEE, 2015-04) Hünerli H. V.; Mopidevi, H.; Cağatay, E.; Imbert, M.; Romeu, J.; Jofre, L.; Çetiner, B. A.; Bıyıklı, Necmi
In this paper we present two antenna designs capable of covering the IEEE 802.11ad (WiGig) frequency band (57-66 GHz and 59-66 GHz respectively). The work below reports the design, microfabrication and characterization of a broadband patch antenna along with the design and microfabrication of multifunction reconfigurable antenna (MRA) in its static form excluding active switching. The first design is a patch antenna where the energy is coupled with a conductor-backed (CB) coplanar waveguide (CPW)-fed loop slot, resulting in a broad bandwidth. The feed circuitry along with the loop is formed on a quartz substrate (at 60 GHz), on top of which an SU-8-based three-dimensional (3D) structure with air cavities is microfabricated. The patch metallization is deposited on top of this structure. The second design is a CB CPW-fed loop slot coupled patch antenna with a parasitic layer on top. The feed circuitry along with the loop is formed on a quartz substrate. On top, the patch metallization is patterned on another quartz substrate. The parasitic pixels are deposited on top of these two quartz layers on top of an SU-8 based 3D structure with air cavities. © 2015 EurAAP.
Open Access
Use of discontinuous expansion and testing functions in the method of moments for electromagnetic problems
(IEEE, 1993-06-07) Aksun, M. Irsadi
The purpose of this paper is to show that there is an additional constraint to be satisfied by the current density when discontinuous expansion functions are used, and the discontinuous expansion and testing functions together can be employed in the application of the MoM in the spatial and spectral domain with the use of this additional constraint.