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ABSTRACT: A novel modified microstrip-fed ultrawide-band (UWB) printed Pythagorean tree fractal monopole antenna is presented. In this letter, by inserting a modified Pythagorean tree fractal in the conventional T-patch, much wider impedance bandwidth and new resonances will be produced. By only increasing the tree fractal iterations, new resonances are obtained. The designed antenna has a compact size of 25 × 25 × 1 mm<sup>3</sup> and operates over the frequency band between 2.6 and 11.12 GHz for VSWR <; 2. Using multifractal concept in modified Pythagorean tree fractal antenna design makes monopole antennas flexible in terms of controlling resonances and bandwidth. In this letter, the improvement process of the impedance bandwidth has been presented and discussed.
IEEE Antennas and Wireless Propagation Letters 02/2011; · 1.37 Impact Factor
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ABSTRACT: This letter presents a new design for a circularly polarized square slot antenna (CPSSA). The proposed single-layer antenna composed of a square ground plane embedded with two unequal-size inverted-L strips around two opposite corners is capable of generating a resonant mode for exciting two orthogonal E vectors. In this model, compared to the previous CPSSA structures, the impedance bandwidth and the axial ratio bandwidth of antenna are increased, which is four times wider than the impedance bandwidth of previous similar designs. The designed CPSS antenna with size 60 × 60 × 0.8 mm<sup>3</sup> operates over the frequency band between 2.67 and 13 GHz (4.74:1, 132%) for VSWR <; 2, exhibiting a 32.2% (4.9-6.9 GHz, 1.5:1) circular polarization (CP) bandwidth. Throughout this letter, the improvement process of the axial ratio (AR) and S\ properties are presented and discussed in detail.
IEEE Antennas and Wireless Propagation Letters 02/2011; · 1.37 Impact Factor
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ABSTRACT: A new form CPW-fed broadband circularly polarized square slot antenna (CPSSA) with three inverted-L-shape grounded strips around the corners of the slot is proposed and fabricated. In comparison to the previous CPSSA structures, the axial-ratio (AR) bandwidth of the antenna is increased, which is two times wider than the previous proposed design. By embedding the L-shape strip to the ground plane and using the vertical stub to the feed line, very good axial-ratio bandwidth is obtained. The measured impedance bandwidth and AR of the realized CPSS antenna with optimized parameters is from 2 to 7 GHz (3.5:1, 110%) for VSWR ≤ 2 and 2-5 GHz (2.5:1; 85%) for AR ≤ 3 dB respectively. Throughout this letter, the improvement process of the AR and S<sub>11</sub> properties is completely presented and discussed.
IEEE Antennas and Wireless Propagation Letters 02/2011; · 1.37 Impact Factor
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ABSTRACT: A compact microstrip ultrawideband (UWB) bandpass filter (BPF) with a narrow notched band in the UWB passband is presented. The narrow notched band was introduced by using a new technique that involves embedding a parasitic coupled line to the UWB BPF in order to reject any undesired existing radio signal that may interfere with the determined UWB passband. The notched band can be easily generated and set at any desired frequency by varying the structural parameters of parasitic coupled line. The design is successfully realized in theory and verified by electromagnetic (EM) simulation and the experiment. This filter can be integrated in UWB radio systems and efficiently enhance the interference immunity from undesired signals such as wireless local area network (WLAN).
IEEE Microwave and Wireless Components Letters 09/2010; · 1.72 Impact Factor
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ABSTRACT: A novel hybrid design of microstrip-fed parasitic-coupled monopole antenna is presented. The proposed antenna structure consists of a directly fed main patch and electromagnetically coupled parasitic patch, both in the semi-ellipse shape. Wider impedance bandwidth can be achieved by carving two sectors on bottom-side of the parasitic patch. An additional inverted semi-ellipse-shaped patch is connected to the main patch to act as a filter structure. The proposed UWB antenna is optimized to operate in the frequency band between 3 to 11 GHz for S<sub>11</sub> < -10 dB, omitting the undesired frequency band of 5.1 to 5.9 GHz. Simulation and experimental results of the prototyped antenna are presented and discussed.
IEEE Transactions on Antennas and Propagation 05/2010; · 2.15 Impact Factor
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ABSTRACT: A new form of a hybrid design of a microstrip-fed parasitic coupled ring fractal monopole antenna with semiellipse ground plane is proposed for modern mobile devices having a wireless local area network (WLAN) module along with a Worldwide Interoperability for Microwave Access (WiMAX) function. In comparison to the previous monopole structures, the miniaturized antenna dimension is only about 25 × 25 × 1 mm<sup>3</sup> , which is 15 times smaller than the previous proposed design. By only increasing the fractal iterations, very good impedance characteristics are obtained. Throughout this letter, the improvement process of the impedance and radiation properties is completely presented and discussed.
IEEE Antennas and Wireless Propagation Letters 02/2010; · 1.37 Impact Factor
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ABSTRACT: In this letter, a novel planar monopole antenna with a variable frequency band-notch characteristic for ultrawideband (UWB) applications is presented. The UWB property is achieved by embedding two shorted rectangular quarter-wavelength resonators. Two other L-shaped quarter-wavelength resonators coupled to the radiating patch are also used in order to generate the frequency band-stop performance and control antenna characteristics such as band-notch frequency and its bandwidth. The designed antenna has a stopband of 5-5.9 GHz while maintaining wideband performance from 3.1 to 11 GHz with VSWR <; 2.
IEEE Antennas and Wireless Propagation Letters 02/2010; · 1.37 Impact Factor
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ABSTRACT: In this letter, a simple rectangular monopole antenna with variable band-notched function is proposed. The antenna is constructed on an FR4-epoxy substrate with thickness of 1.6 mm and ε<sub>r</sub> = 4.4. The proposed antenna shows ultrawideband (UWB) characteristics from around 3 up to 10.6 GHz for . Two shorting pins running through the substrate connect the patch to the inverted L-shaped stubs printed on the bottom of the substrate to create multifiltering function. By changing the stubs' lengths, the proposed antenna shows variable single- and double-filtering characteristics.
IEEE Antennas and Wireless Propagation Letters 02/2010; · 1.37 Impact Factor
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ABSTRACT: A novel modified band-rejected circle-like slot antenna with a folded fork-shaped tuning stub, for various UWB applications, is proposed. To achieve band-rejected filtering property at the 5 GHz WLAN bands, the forked-shaped strips are folded back and result in a pair of coupled lines on the tuning stub. Moreover, by optimising the dimensions of the fork-shaped tuning stub, the total bandwidth of the antenna can be greatly improved up to 156%. Measured results show that the realised antenna operates over 2.2-18 GHz for VSWR < 2 and has the notched band from 5.1 to 6.2 GHz.
Electronics Letters 01/2010; · 0.96 Impact Factor
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ABSTRACT: A dual band-notched printed ultrawideband monopole antenna is presented, with a modified ground plane. By using this modified element including a pair of variable L-shaped slots, cut in the ground plane, additional resonances are excited and hence the bandwidth is increased up to 130%. To generate single and dual band-notched characteristics, we use inverted U- and fork-shaped parasitic structures, respectively, instead of changing the patch or feedline shapes. By properly adjusting the dimensions of these capacitive-coupled elements, not only one or two controllable notch resonances are achieved, but also the lower-edge frequency of the band is decreased. The measured results show that the proposed dual band-notched monopole antenna offers a very wide bandwidth from 2.2 to 13.4 GHz (143%), defined by 10-dB return loss, with two notched bands, covering all the 5.2/5.8-GHz WLAN, 3.5/5.5-GHz WiMax and 4-GHz C bands. Impedance, radiation, efficiency and gain characteristics of the antenna are also discussed.
IEEE Transactions on Antennas and Propagation 01/2010; · 2.15 Impact Factor
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ABSTRACT: A novel modified printed ultra-wideband (UWB) slot antenna with a square structure and a trapezoid tuning stub as well as a band-notch characteristic is presented. By embedding two L-shaped slits at the edge of the open radiating slot, a tunable notched band, for avoiding interference between the UWB and WLAN systems, is achieved. Moreover, by optimising the dimensions of the polygon-like slot and tuning stub, the impedance bandwidth and matching of the antenna can be improved. The realised slot antenna operates over 2.6-13.6 GHz for VSWR < 2 and has a rejected band of 4.9-5.85 GHz.
Electronics Letters 11/2009; · 0.96 Impact Factor
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ABSTRACT: In this letter, we present a novel printed monopole antenna for ultrawideband (UWB) applications. The proposed antenna consists of a square radiating patch with two rectangular slots and a ground plane with inverted T-shaped notch, which provides a wide usable fractional bandwidth of more than 120% (3.1212.73 GHz). The proposed antenna is simple and small in size. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB frequency range.
IEEE Antennas and Wireless Propagation Letters 02/2009; · 1.37 Impact Factor
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ABSTRACT: A novel modified microstrip-fed ultrawideband (UWB) planar monopole antenna with variable frequency band-notch characteristic is presented. By inserting two slots in the both sides of microstrip feedline on the ground plane, much wider impedance bandwidth can be produced. A modified H-shaped conductor-backed plane with variable dimensions is used in order to generate the frequency band-stop performance and control its characteristics such as band-notch frequency and its bandwidth. The designed antenna has a small size of 22 x 22 mm<sup>2</sup> and operates over the frequency band between 3.1 and 14 GHz for VSWR < 2 while showing the band rejection performance in the frequency band of 5.1 to 5.9 GHz.
IEEE Antennas and Wireless Propagation Letters 02/2008; · 1.37 Impact Factor
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ABSTRACT: By using of a new coplanar waveguide feeding (CPW feeding) technique to a planar sleeve monopole, a narrow width antenna with uniplanar structure is proposed for dual band operation at UMTS (1.885-2.200 GHz) and HIPERLAN2 (5.470- 5.725 GHz) bands. Proposed antenna has considerable narrow width (width of 7.8 mm) and simple structure. The antenna radiation pattern is almost as the radiation pattern of a monopole antenna and the gain remains nearly constant within UMTS and HIPERLAN2 bands. The antenna is suitable for application to wireless communication systems.
Antennas, Propagation & EM Theory, 2006. ISAPE '06. 7th International Symposium on; 11/2006
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ABSTRACT: This paper presents a new method to reduce stray signal errors in antenna radiation pattern measurement using RLS algorithm (recursive least-squares algorithm). Stray signals create by reflection and scattering of the range antenna field from fixed objects in the range and by leakage of the range RF system. This method can be used on static far-field range. In this method, an antenna with the known pattern (reference antenna) is placed in the test zone to find the optimal tap weights of the RLS algorithm. By the optimal tap weights, radiation pattern of AUT (antenna under test) is corrected. The effectiveness of this method is confirmed by some simulation results.
Microwave Conference Proceedings, 2005. APMC 2005. Asia-Pacific Conference Proceedings; 01/2006
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ABSTRACT: The ionosphere, the region of the upper atmosphere, varies strongly with frequency; this provides some properties in the ionosphere region which make radiowave propagation more complicated. We propose a new method, based on phasors of the voltage, V, and on the solution of the Laplace equation, to compute the effective B in arbitrary points of space. This method is implemented easily and solved in different conditions.
Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005
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ABSTRACT: In this paper a novel reduced size and wideband fractal patch antenna is introduced. Because of it's likeness to butterfly it has been named fractal butterfly patch antenna. By its comparison to conventional square patch antenna more than 68% size reduction at third iteration of fractal is achieved. Then by utilizing a T-probe feeding method, up to 13 % impedance bandwidth (VSWR 2) is obtained as well as 60% reduction in size. Finally a broadband antenna proposed as a miniaturized wide band patch antenna for personal communication systems.
Wireless Communications and Applied Computational Electromagnetics, 2005. IEEE/ACES International Conference on; 05/2005
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ABSTRACT: Cumulative probability distribution (CPD) is a statistical approach in the comparison of multi-path fading models. One problem encountered in this comparison method is its inability to distinguish between certain sets of data. This problem is covered thoroughly and a solution is discussed for overcoming it. The overall new method is named 'new forms of CPD' (NFCPD). These three new forms are: simple sigma-r (SSR), complex sigma-r (CSR) and the 3-D mesh method. Each method has been covered thoroughly and shown to correct CPD's incompleteness, and although all three methods are very similar in structure and algorithms, each has a unique use of its own. Also, new applications of SSR are proposed in three fields: communication channel recognition, channel distortion measurement, and MTI radars. Although all results presented are obtained from SSR, they could also be obtained by CSR and the 3-D mesh method. SSR has been chosen because of its simplicity and relative accuracy.
IEE Proceedings - Communications 03/2005; · 0.32 Impact Factor
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ABSTRACT: A new technique to compensate for the mutual coupling effect in small phased array antennas is presented. This method is a modification to the classical approach for correcting the array output vector by multiplication of a decoupling matrix to achieve a less unperturbed array response. Two different methods of calculating coupling coefficients between array elements are presented. The performance is demonstrated by a simulation based on a numerical analysis with the finite element method (FEM) and a practical application to a digital beamforming (DBF) array.
Antennas and Propagation Society International Symposium, 2004. IEEE; 07/2004
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ABSTRACT: A deterministic approach to model radio propagation channels in
complex environments and use the model to study diversity techniques is
described. The simulation is based on geometric optics and uses
ray-tracing techniques. The effects of all rectangular obstacles are
considered by the model. Both reflection and refraction effects are
taken into account. Simulation results are presented and the reliability
of these results is examined by comparing them with those obtained from
measurements at 60 GHz. Also it is shown that it is possible to minimise
the simulation time of the model by an appropriate choice of cell size.
The model is seen to be able to investigate delay spread in an
environment in considerable detail. The performance of space, frequency
and polarisation diversity is investigated by use of the model. The
results show that space diversity is better than polarisation or
frequency diversity in the environments examined
IEE Proceedings - Microwaves Antennas and Propagation 09/1998; · 0.49 Impact Factor
