# Browsing by Subject "Antenna radiation"

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Item Open Access Application of signal-processing techniques to dipole excitations in the finite-difference time-domain method(Taylor & Francis, 2002) Oğuz, U.; Gürel, LeventShow more The applications of discrete-time signal-processing techniques, such as windowing and filtering for the purpose of implementing accurate excitation schemes in the finite-difference time-domain (FDTD) method are demonstrated. The effects of smoothing windows of various lengths and digital lowpass filters of various bandwidths and characteristics are investigated on finite-source excitations of the FDTD computational domain. Both single-frequency sinusoidal signals and multifrequency arbitrary signals are considered.Show more Item Open Access Artificial olfaction inside nanostructured infrared fiber arrays(IEEE, 2011) Yaman, Mecit; Yıldırım, Adem; Bayındır, MehmetShow more Nanostructured hollow core fibers are used to demonstrate a new infrared absorption based artificial nose. The sensor unit of the array is a hollow core Bragg fiber that selectively guides incident blackbody radiation and enhances absorption for enhanced sensitivity. © 2011 IEEE.Show more Item Open Access Complex source radiation in a cylindrical radome of metal-dielectric grating(IEEE, 1999) Altintas, A.; Ouardani, S.; Yurchenko, V. B.Show more The radiation fields of a line source enclosed in a circular dielectric radorne with grating consisting of an array of thin lossy metal strips are analyzed. The variations of the directivity of the source beam with respect to the beam direction are studied. The possibility of damping these variations by an appropriate design of the radome is demonstrated.Show more Item Open Access Hybrid model for probe-fed rectangular microstrip antennas with shorting pins(IEEE, 2000) Mutlu, Selma; Aksun, M. İrşadiShow more 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.Show more Item Open Access Radiation characteristics of a 2D parabolic reflector antenna excited by the H-polarized complex source(IEEE, 2002-09) Oğuzer, T.; Nosich, A. I.; Altıntaş, AyhanShow more The aim of this paper is to obtain accurate reference data for relatively large and realistic reflector antenna systems. We concentrate on a parabolic reflector antenna in the H-polarization case. The directive primary feed is modeled by the complex source point method and the relative accuracy of the results is verified. © 2002 IEEE.Show more Item Open Access Solution of radiation problems using the fast multipole method(IEEE, 1997-07) Gürel, Levent; Şendur, İbrahim KürşatShow more Electromagnetic radiation problems involving electrically large radiators and reflectors are solved using the fast multipole method (FMM). The FMM enables the solution of large problems with existing computational resources by reducing the computational complexity by a faster equivalent of O(N) complexity in each iteration of an iterative scheme. Three dimensional radiation problems involving complicated geometries are modeled using arbitrary surface triangulations. Piecewise linear basis functions defined on triangular domains due to Rao, Wilton, and Glisson (RWG) basis functions are used to approximate the induced currents. Using delta-gap voltage sources and prescribed current distributions, the operations of various antennas are simulated.Show more Item 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, NecmiShow more 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.Show more Item Open Access Use of discontinuous expansion and testing functions in the method of moments for electromagnetic problems(IEEE, 1993-06-07) Aksun, M. IrsadiShow more 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.Show more