Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
Browse
9 results
Search Results
Article Citation - WoS: 5Citation - Scopus: 6Novel Square Spiral Antennas for Broadband Applications(Walter de Gruyter GmbH, 2009) Saynak, Uğur; Kuştepeli, AlpAn investigation of novel square spiral antennas is presented. The antennas are designed by considering the special arrangements of spiral arms. The new designs perform much better in terms of the frequency independency of the fundamental antenna parameters, when compared with the well known and widely used Archimedean spiral antenna, which makes the antennas very suitable for broadband wireless applications. Experimental results are also presented and there is a good agreement between the measured and numerical data.Other Citation - WoS: 2Citation - Scopus: 1Erratum To: Multi-Band Cpw Fed Mimo Antenna for Bluetooth, Wlan, and Wimax Applications(John Wiley and Sons Inc., 2017) Deste, İrem; Bozdağ, Göksenin; Kuştepeli, AlpIn the above-mentioned article, which appeared in Microwave and Optical Technology Letters, Volume 58#9, DOI 30001, the captions for Figure 1 and Figure 4 were published incorrectly. The corrections are shown below: Figure 1 Element antenna (a) Geometry (b) Fabricated (a = 12.5 mm, b = m = v = o = 0.5 mm, c = 4 mm, d = n = 15 mm, e = h = 3 mm, f = 14 mm, g = 16 mm, i = 7 mm, k = 1.5 mm, l = 12 mm, p = 1.25 mm, r = 1.64 mm, s = 1.7 mm, t = 1.94 mm, u = 11.1 mm, w = 0.3 mm). [Color figure can be viewed at wileyonlinelibrary.com] Figure 4 Fabricated MIMO antenna (d1 = d3 = 7 mm, d2 = 10 mm, d4 = 12 mm). [Color figure can be viewed at wileyonlinelibrary.com] In addition, Figure 6 was published with an error. The corrected figure is shown below: The publisher regrets any confusion caused by these errors. (Figure presented.).Other Citation - WoS: 1Erratum: Wideband Planar Monopole Antennas for Gps/Wlan and X-Band Applications (microwave and Optical Technology Letters 58:2)(John Wiley and Sons Inc., 2016) Bozdağ, Göksenin; Kuştepeli, AlpArticle Citation - WoS: 5Citation - Scopus: 9Wideband Planar Monopole Antennas for Gps/Wlan and X-Band Applications(John Wiley and Sons Inc., 2016) Bozdağ, Göksenin; Kuştepeli, AlpIn this article, two printed planar monopole antennas (PPMA) are presented. In the design of the first PPMA, the structure is divided into sections and they are optimized in the sense of bottom to up strategy. Tapered transitions and inset feed are employed to increase the bandwidth. The antenna operates between 2.37 GHz and 12 GHz with VSWR<2 and an average peak realized gain of 4.95 dB. Therefore, it is suitable for WLAN, WiMAX, UWB, and X-Band applications. The second PPMA is designed by implementing slots on the previous one to include GPS. The resulting antenna operates in the 1.38-1.60 GHz and 2.33-13.74 GHz bands with VSWR<2. As a result, it also includes GPS in addition to the previous bands. The peak realized gain in GPS is 0.47 dB at 1.575 GHz and the average peak realized gain is 4.41 dB for the 2.33-13.74 GHz band. The group delay performances of the proposed PPMAs are also examined and the maximum group delay deviations of the first and the second PPMAs are observed as 1 ns and 1.33 ns, respectively.Article Citation - WoS: 10Citation - Scopus: 10On the Helmholtz Theorem and Its Generalization for Multi-Layers(Taylor and Francis Ltd., 2016) Kuştepeli, AlpThe decomposition of a vector field to its curl-free and divergence-free components in terms of a scalar and a vector potential function, which is also considered as the fundamental theorem of vector analysis, is known as the Helmholtz theorem or decomposition. In the literature, it is mentioned that the theorem was previously presented by Stokes, but it is also mentioned that Stokes did not introduce any scalar and vector potentials in his expressions, which causes a contradiction. Therefore, in this article, Stokess and Helmholtzs representations are examined in detail to reveal and emphasize their differences, similarities and important points. The Helmholtz theorem is obtained for all kinds of spaces by using the theory of distributions in a comprehensive and rigorous manner with detailed explanations, which also leads to a new surface version of the Helmholtz theorem or a new surface decomposition, resulting in the canonical form; hence, it is different than the one suggested previously in terms of two scalar functions. The generalized form of the Helmholtz theorem is also presented by employing the same approach when there is a multi-layer on the surface of discontinuity, which also corresponds to the extension of the theorem to fields with singularities of higher order.Article Citation - WoS: 13Citation - Scopus: 18Multi-Band Cpw Fed Mimo Antenna for Bluetooth, Wlan, and Wimax Applications(John Wiley and Sons Inc., 2016) Desde, İrem; Bozdağ, Göksenin; Kuştepeli, AlpIn this letter, multi-band coplanar waveguide (CPW) fed multiple-input-multiple-output (MIMO) antenna is presented for Bluetooth, WLAN and WiMAX applications. The elements of MIMO antenna are identical CPW-fed printed monopole antennas whose bandwidth performances are improved by employing inverse U and meander line slots. In the design of the antennas, a low-cost FR4 substrate is used and the size of the element antennas are optimized as 35 mm x 30 mm. According to the measurements, S11 is below −10 dB in 2.38 GHz – 2.52 GHz and 3.19 GHz – 6.44 GHz bands with 0.2 dB and 2.9 dB average peak realized gains, respectively. The element antennas are placed orthogonally and fed independently to obtain MIMO structure whose size is optimized as 42 mm x 62 mm. The performance of MIMO antenna is also examined in terms of diversity parameters such as envelope correlation coefficient and apparent diversity gain, which are lower than 0.02 and higher than 9.9 in the operating bands, respectively.Article Citation - WoS: 1Citation - Scopus: 1Revised Distributional Forms of the Laplacian and Poisson's Equation, Their Implications, and All Related Generalizations(Taylor and Francis Ltd., 2015) Kuştepeli, AlpThe theory of distributions of L. Schwartz is a very useful and convenient way for the analysis of physical problems since physical distributions, especially charge distributions yielding the discontinuity of the potential and boundary conditions, can be correctly described in terms of mathematical distributions. To obtain the charge distributions, the distributional form of the Laplacian is applied to the Poisson's equation; therefore, for the correct representations and interpretations, the distributional forms and their proper applications are very important. In this article, it is shown that the distributional form of the Laplacian has been presented by Schwartz and also others with a missing term, leading to confusing and wrong results mathematically, and as a result electromagnetically; and the revised, correct, and complete distributional representations of the Laplace operator, the Poisson equation, and double layers, defined as the dipole layer and equidensity layer, are obtained and presented with detailed discussions and explanations including boundary conditions. By using the revised form of the Laplacian, Green's theorem is obtained explicitly with special emphases about important points and differences with previous works. The generalized forms of the Laplacian, Poisson's equation, charge densities, boundary conditions, and Greens theorem are also presented when there is a multi-layer on the surface of discontinuity.Article Citation - WoS: 12Citation - Scopus: 16The Resonant Behavior of the Fibonacci Fractal Tree Antennas(John Wiley and Sons Inc., 2008) Özbakış, Başak; Kuştepeli, AlpAn investigation of a novel fractal tree antenna with the application to two different geometries is presented. The antenna is designed by using the special Fibonacci number sequence which leads to nonuniform branch length ratios to form the fractal tree. This new approach gives better performance, especially in the miniaturization of the antenna, when compared with the conventional designs. The results obtained from the experiments are also compared with the computed ones and there is a very good agreement between the numerical and measured data.Article Citation - WoS: 2Citation - Scopus: 1Design of Coupling Structures for Groove Guide Resonators(John Wiley and Sons Inc., 2008) Bechteler, Thomas F.; Kuştepeli, Alp; Aydınlık Bechteler, Ayşe SevinçThree different coupling structures for a groove guide resonator operating at 10 GHz are investigated. First, propagatable modes are determined analytically. Then, the efficiency of the coupling structures is investigated by means of the method of moments and measurements. Finally, a groove guide resonator is designed and the resonance spectrum for each coupling structure is computed numerically, applying the finite-difference time-domain method. Numerical results are compared with experimental measurements. There is good agreement between the measured and simulated data.