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Showing papers in "IEEE Antennas and Wireless Propagation Letters in 2005"


Journal ArticleDOI
TL;DR: In this article, a defected ground structure (DGS) pattern is proposed to reduce the cross-polarized (XP) radiation of a microstrip patch antenna, which is simple and easy to etch on a commercial microstrip substrate.
Abstract: A defected ground structure (DGS) is proposed to reduce the cross-polarized (XP) radiation of a microstrip patch antenna. The proposed DGS pattern is simple and easy to etch on a commercial microstrip substrate. This will only reduce the XP radiation field without affecting the dominant mode input impedance and co-polarized radiation patterns of a conventional antenna. The new concept has been examined and verified experimentally for a particular DGS pattern employing a circular patch as the radiator. Both simulation and experimental results are presented.

275 citations


Journal ArticleDOI
TL;DR: In this article, a low-profile metamaterial ring antenna using two MCU cells is proposed using negative-refractive-index (NRI) microstrip transmission lines (TL) designed to incur a zero insertion phase at the antenna design frequency.
Abstract: A compact (/spl lambda//sub 0//11 footprint) and low-profile (/spl lambda//sub 0//28 height) metamaterial ring antenna is proposed using two metamaterial unit cells. Each constituent unit cell consists of negative-refractive-index (NRI) microstrip transmission lines (TL) designed to incur a zero insertion phase at the antenna design frequency. This allows the inductive posts to ground, which act as the main radiating elements, to be fed in phase. Hence, the antenna operates as two closely spaced monopoles that are fed in phase through a compact feed network. An embedded matching network ensures good VSWR performance. The theoretical performance of the antenna is verified by full-wave simulations and experimental data obtained from a fabricated prototype at 1.77 GHz. The antenna offers a 120 MHz -10 dB bandwidth and a measured efficiency exceeding 50%.

219 citations


Journal ArticleDOI
Paul Hallbjörner1
TL;DR: In this article, the correlation coefficient between signals received by two antennas can be calculated from port S-parameters and the effect of antenna radiation efficiencies have on the calculated correlation is discussed.
Abstract: The correlation coefficient between signals received by two antennas can be calculated from port S-parameters Antenna radiation efficiencies must, however, also be considered They result in an uncertainty in the calculated received signal correlation, if the correlation between the losses is unknown, which is often the case Relations are presented for the effect antenna efficiencies have on the calculated correlation

214 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented a low-cost knight's helm shape double-sided printed circuit board (PCB) antenna of size 3 cm/spl times/3 cm for ultra-wideband (UWB) application.
Abstract: This letter presents a low-cost knight's helm shape double-sided printed circuit board (PCB) antenna of size 3 cm/spl times/3 cm for ultra-wideband (UWB) application. The antenna has a return loss of more than 10 dB, constant group delay and gain flatness over the frequency range set by the Federal Communications Commission (FCC) for UWB application. Satisfactory performance was obtained using FR4 substrate, allowing low cost of production. This letter also addresses the experimental measurements of group delay and impulse response, which are commonly overlooked.

207 citations


Journal ArticleDOI
TL;DR: In this article, the effect of two different antenna types on radio propagation in ultrawideband (UWB) on-body channel measurement is analyzed, and the hybrid use of different type UWB antennas can effectively improve channel behavior in body-centric wireless networks.
Abstract: The effect of two different antenna types on radio propagation in ultrawideband (UWB) on-body channel measurement are analyzed. Statistical path loss parameters and time domain channel characteristics [mean delay and root mean square (rms) delay spread] are extracted from measurement data. Reduction in rms delay spread is experienced when using printed horn shaped self-complementary antennas (HSCA) for specific body area links in comparison to monopole-like omnidirectional antennas, e.g., planar inverted cone antennas (PICA). Results show that the hybrid use of different type UWB antennas can effectively improve channel behavior in body-centric wireless networks.

206 citations


Journal ArticleDOI
TL;DR: In this paper, a dual-band circularly polarized patch antenna dedicated to satellite communications is presented, which is obtained by inserting a small X-band microstrip patch antenna into a large L-band one.
Abstract: This letter presents a dual-band circularly polarized patch antenna dedicated to satellite communications. The dual-band behavior is obtained by inserting a small X-band microstrip patch antenna into a large L-band one. Both patches are printed on the same substrate and fed by electromagnetic coupling through two perpendicular slots etched in their ground planes. These slots are fed by two different 90/spl deg/ microstrip branch-line couplers printed on a stacked lower substrate. A prototype of the antenna was realized with a 1.5-mm-thick upper layer substrate and a 0.758-mm-thick feed layer substrate, both of the same dielectric material with a relative permittivity of /spl epsiv//sub r/=2.22. Simulation and measurement results are presented, showing this compact dual-band antenna achieves the required Meteosat specifications in terms of frequency bandwidth, circular polarization bandwidth, and isolation between the two communication bands.

189 citations


Journal ArticleDOI
TL;DR: In this paper, a metamaterial balun that converts a single-ended input to a differential output over a large bandwidth is presented, which exhibits excellent return loss, isolation, and through characteristics over the same frequency band.
Abstract: A metamaterial balun that converts a single-ended input to a differential output over a large bandwidth is presented. The device also exhibits excellent return loss, isolation, and through characteristics over the same frequency band. The balun comprises a Wilkinson divider, followed by a +90/spl deg/ negative-refractive-index (NRI) metamaterial (MM) phase-shifting line along the top branch, and a -90/spl deg/ MM phase-shifting line along the bottom branch. Utilizing MM lines for both the +90/spl deg/ and -90/spl deg/ branches allows the slopes of their phase responses to be matched, resulting in a broadband differential output signal. The theoretical performance of the balun is verified through circuit simulations and measurements of a fabricated prototype at 1.5 GHz. The MM balun exhibits a measured differential output phase bandwidth (180/spl deg//spl plusmn/10/spl deg/) of 1.16 GHz (77%), from 1.17 to 2.33 GHz. The measured isolation and return loss for all three ports remain below -10 dB over a bandwidth in excess of 2 GHz, while the output quantities |S/sub 21/| and |S/sub 31/| remain above -4 dB from 0.5 to 2.5 GHz.

183 citations


Journal ArticleDOI
TL;DR: In this article, a new technique is presented from another point of view, which reconstructs a special antenna array model based on the Toeplitz matrix whose rank is only related to the DoA of signals and cannot be affected by the coherency between them.
Abstract: Conventionally, the approaches to coherent direction-of-arrival (DOA) estimation are to eliminate the rank loss of the spatial covariance matrix. In this letter, a new technique is presented from another point of view, which reconstructs a special antenna array model based on the Toeplitz matrix whose rank is only related to the DOA of signals and cannot be affected by the coherency between them. Therefore, the signal and noise subspaces can be estimated properly. In conjoint with the improved estimation of signal parameter via rotational invariance techniques (ESPRIT) algorithm, it is capable of resolving the DOAs of coherent signals as well as uncorrelated signals without peak searching. The numerical examples demonstrate its validity.

173 citations


Journal ArticleDOI
TL;DR: The performance of smart antennas with uniform circular arrays (UCAs) with symmetry provides UCAs a major advantage, the ability to scan a beam azimuthally through 360/spl deg/ with little change in either the beamwidth or the sidelobe level.
Abstract: Numerous studies for smart antennas have already been conducted. However, these studies include mostly uniform linear arrays (ULAs) and uniform rectangular arrays (URAs) and not as much effort has been devoted to other configurations. In this letter, the performance of smart antennas with uniform circular arrays (UCAs) is examined. The primary motivation for this selection is the symmetry UCAs possess. This property provides UCAs a major advantage, the ability to scan a beam azimuthally through 360/spl deg/ with little change in either the beamwidth or the sidelobe level. Also, a comparison between UCAs and URAs in the context of adaptive beamforming is made in this letter.

159 citations


Journal ArticleDOI
TL;DR: The design of a low-cost rectenna for low-power applications is presented with the use of analytical models and closed-form analytical expressions, which allows for a fast design of the rectenna system.
Abstract: The design of a low-cost rectenna for low-power applications is presented. The rectenna is designed with the use of analytical models and closed-form analytical expressions. This allows for a fast design of the rectenna system. To acquire a small-area rectenna, a layered design is proposed. Measurements indicate the validity range of the analytical models.

158 citations


Journal ArticleDOI
TL;DR: In this article, the effects of metallic plate size on the performance of microstrip patch-type tag antennas were analyzed based on finite element method (FEM) simulations and practical read-range measurements.
Abstract: Metallic objects are challenging for passive ultra high frequency (UHF) spectrum radio frequency identification (RFID) systems due to the effects of conductive materials on tag antenna performance. In this letter, we analyze the effects of metallic plate size on the performance of microstrip patch-type tag antennas. Microstrip patch antennas with regular ground plane and electromagnetic band gap (EBG) ground plane are studied attached to two differently sized metallic plates. Analysis is based on finite element method (FEM) simulations and practical read-range measurements.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a hybrid "damping" boundary condition that combines the characteristics offered by the existing absorbing and reflecting boundaries to obtain a robust and consistent optimization performance for PSO regardless of the dimensionality and location of the global optimum solution.
Abstract: The particle swarm optimization (PSO) technique is a powerful stochastic evolutionary algorithm that can be used to find the global optimum solution in a complex search space. However, it has been observed that there is a great variation in its performance due to the dimensionality of the problem and the location of the global optimum with respect to the boundaries of the search space. The present paper attempts to resolve this problem by proposing a simple hybrid "damping" boundary condition that combines the characteristics offered by the existing "absorbing" and "reflecting" boundaries. Simulation results on microwave image reconstruction have shown that with the proposed "damping" boundary condition, a much robust and consistent optimization performance can be obtained for PSO regardless of the dimensionality and location of the global optimum solution.

Journal ArticleDOI
TL;DR: An algorithm for precise determination of the distance between a pair of transmitting and receiving antennas using FCC conforming ultra-wideband (UWB) pulses is presented, achieving centimeter level accuracy.
Abstract: This paper presents an algorithm for precise determination of the distance between a pair of transmitting and receiving antennas using FCC conforming ultra-wideband (UWB) pulses. Indoor line-of-sight (LOS) measurements up to 24 m were conducted at Research Technoplaza, Nanyang Technological University, Singapore. The proposed algorithm is developed using Matlab to post process the captured waveform. Significant improvement of accuracy is observed in determining the time of flight using a combination of match filtering and peak search technique, achieving centimeter level accuracy. Ranging results show a worst case standard deviation of 2 cm for distance up to 8 m and 10.6 cm for distance up to 24 m.

Journal ArticleDOI
TL;DR: In this paper, a rectifying antenna (rectenna) designed in a finite ground coplanar waveguide (FG-CPW) circuit is presented, which is based on a new patch antenna and a new band-stop filter, in the form of compact CPW resonant cell (CCRC), located between the antenna and the rectifying diode.
Abstract: This paper presents a rectifying antenna (rectenna) designed in a finite ground coplanar waveguide (FG-CPW) circuit. The new rectenna element is based on a new patch antenna and a new band-stop filter, in the form of compact CPW resonant cell (CCRC), located between the antenna and the rectifying diode. The novel coplanar patch antenna with about 9-dBi gain is proposed for the rectenna. The CCRC is adopted to suppress the second harmonic from radiation. With the use of this band-stop filter, a radio-frequency-to-direct-current (RF-to-dc) conversion efficiency of 68.5% using a 270-/spl Omega/ load resistor is obtained.

Journal ArticleDOI
TL;DR: This letter proposes a circularly polarized (CP) microstrip patch antenna that can function as a WLAN antenna in the 5.15-5.35 GHz range and as a rectenna at 5.5 GHz.
Abstract: Small distributed wireless sensors are becoming very important in many aspects of our lives. While low data rate passive sensors operate with little energy there is a need for moderate to high data rate distributed sensors for infrastructure monitoring and other applications. Such sensors will require their batteries or onboard capacitors to be charged when depleted for proper operation. In this letter, we propose a circularly polarized (CP) microstrip patch antenna that can function as a WLAN antenna in the 5.15-5.35 GHz and as a rectenna at 5.5 GHz.

Journal ArticleDOI
TL;DR: In this paper, a dual-band antenna with double L-slits for wireless local area network (WLAN) applications in IEEE 802.11a/b/g is presented.
Abstract: This letter presents a compact dual-band antenna with double L-slits for wireless local area network (WLAN) applications in IEEE 802.11a/b/g. The proposed antenna effectively covers both 2.4/5-GHz bands with three resonances that are caused by the double L-slits. The proposed antenna has compact size of 15 mm/spl times/9 mm/spl times/7 mm, which is only half size of the antenna using double U-slots. The parametric study is performed to understand the characteristics of the proposed antenna. The measured return loss and radiation patterns indicate the suitability of this antenna for the WLAN applications. The peak antenna gains of 1.3 dBi at 2.4-GHz band and 5.1 dBi at 5-GHz band are measured.

Journal ArticleDOI
TL;DR: In this paper, the development of dual-frequency (14 and 35 GHz), dual-polarization microstrip antenna arrays is presented for the first time on liquid crystal polymer (LCP) multilayer technology.
Abstract: The development of dual-frequency (14 and 35 GHz), dual-polarization microstrip antenna arrays is presented for the first time on liquid crystal polymer (LCP) multilayer technology. Some of the properties of LCP, such as multilayer (three-dimensional) vertical integration capability, good electrical and mechanical properties, and near-hermetic nature, make this substrate a practical choice for the design of low-cost antenna arrays that can be integrated with remote sensing applications operating in the Ku and millimeter-wave frequency bands. This work illustrates the potential of LCP as a low-cost, "all-package" solution for developing compact, flexible, antenna arrays that can be used in future communication and remote sensing systems.

Journal ArticleDOI
TL;DR: In this article, the influence of a left-handed medium (LHM) on the performances of a circular patch antenna is quantified numerically, and a homogenization procedure of the LHM is carried out in order to design the patch antenna at a suitable frequency where the losses of LHM are low.
Abstract: The influence of a left-handed medium (LHM) on the performances of a circular patch antenna is quantified numerically. For this, a homogenization procedure of the LHM is carried out in order to design the patch antenna at a suitable frequency where the losses of the LHM are low. From the first results obtained, it is noted that in the presence of the LHM, the antenna is more directive and has a higher gain.

Journal ArticleDOI
TL;DR: In this article, a very low-profile planar horn antenna is proposed, which consists of a subwavelength aperture placed into a concentric periodic corrugated conducting plate that produces good return losses and a narrow radiated beam.
Abstract: In this letter, a very low-profile planar horn antenna is proposed. It consists of a subwavelength aperture placed into a "Bull's Eye" concentric periodic corrugated conducting plate that produces good return losses and a narrow radiated beam. The antenna is excited by means of a waveguide whose flange has been properly mechanized in the rear part of the structure. The mechanism explaining this phenomenon is similar to the enhanced transmission observed at optical wavelengths in similar structures. In this work, the circularly corrugated structure has been scaled into the microwave frequency range and, moreover, the plane wave excitation has been replaced by a subwavelength aperture excited by a conventional closed metallic waveguide. This transforms the original focusing structure into a new concept of a very low-profile feeder with potential applications.

Journal ArticleDOI
TL;DR: In this paper, a singularity extraction method is introduced for the efficient and accurate computation of the outer integrals, similar to the way inner-integral singularities are handled.
Abstract: In the solution of the magnetic-field integral equation (MFIE) by the method of moments (MOM) on planar triangulations, singularities arise both in the inner integrals on the basis functions and also in the outer integrals on the testing functions. A singularity-extraction method is introduced for the efficient and accurate computation of the outer integrals, similar to the way inner-integral singularities are handled. In addition, various formulations of the MFIE and the electric-field integral equation are compared, along with their associated restrictions.

Journal ArticleDOI
Anping Zhao1, Jussi Rahola1
TL;DR: In this article, a quarter-wavelength ultra-wideband (UWB) slot antenna for 3-5 GHz mobile applications is proposed and the performance of the antenna is insensitive to the size of the ground plane and an optimal performance can be easily obtained by varying the dimensions of the slot and tuning stubs.
Abstract: In this letter, a quarter-wavelength ultra-wideband (UWB) slot antenna for 3-5 GHz mobile applications is proposed. Numerical results indicate that the performance of the antenna is insensitive to the size of the ground plane and an optimal performance of the antenna can be easily obtained by varying the dimensions of the slot and tuning stubs. Furthermore, a prototype of the antenna is made and a good agreement between simulation and measurement is achieved.

Journal ArticleDOI
TL;DR: In this article, a dual-polarized broadband horn antenna with a coaxial line to quadruple-ridged waveguide transition was proposed to improve the return loss performance of the horn antenna.
Abstract: This letter describes a new design of dual-polarized broadband horn antennas. The bandwidth of the designed horn antenna is from 2 to 26.5 GHz. A novel coaxial line to quadruple-ridged waveguide transition is introduced to improve the return loss performance of the horn antenna. Measured results for VSWR, isolation, gain, and radiation pattern of the designed horn antenna are presented.

Journal ArticleDOI
TL;DR: In this paper, a planar inverted-F antenna (PIFA) is proposed to operate in the IEEE 802.11b/g, HIPERLAN2 and IEEE 802.,11a/g frequency bands.
Abstract: A novel compact planar inverted-F antenna (PIFA) to be mounted on laptop computers is presented. The proposed multiband single-feed PIFA simultaneously operates in the IEEE 802.11a, IEEE 802.11b/g, and HIPERLAN2 frequency bands. The multiband behavior is obtained by combining a trapezoidal feed plate with two different resonance paths in the radiating structure. The overall size of the antenna renders it suitable to be installed at the border of the display of a notebook. Simulation results are compared with measurements performed on an antenna prototype.

Journal ArticleDOI
TL;DR: In this paper, the design and testing of a wide-band monopolar wire-patch antenna is presented, which consists of a circular patch that is shorted to the ground plane by four copper wires and is fed by an L-probe at its center.
Abstract: This paper presents the design and testing of a wide-band monopolar wire-patch antenna. The proposed antenna consists of a circular patch that is shorted to the ground plane by four copper wires and is fed by an L-probe at its center. For the patch height and patch radius of 0.092 and 0.179 free space wavelengths at 0.893 GHz, this antenna possesses a 14-dB return loss bandwidth of 27.1%, which is 9 times wider than that of similar type of antenna reported in the literature. Also, it has an average gain of 2.6 dBi and monopole-like radiation patterns over this bandwidth. As this antenna has wide impedance bandwidth and relatively small size, it is very suitable for the indoor mobile communication systems.

Journal ArticleDOI
TL;DR: In this paper, a broadband inverted L-shaped dielectric resonator antenna (DRA) is proposed for multiband wireless communication applications as digital communication systems, personal communication systems (PCS), universal mobile telecommunication systems (UMTS), and wireless local area networks (WLANs), which offers a bandwidth of 38% (from 1.71 to 2.51 GHz) and stable broadside radiation patterns.
Abstract: In this letter, a broadband inverted L-shaped dielectric resonator antenna (DRA) is proposed. The DRA with the two equiangular-triangle across sections is built on a ground plane and excited by a coaxial probe to provide broadside radiation patterns. The simulated and measured results verify that the proposed antenna offers a bandwidth of 38% (from 1.71 to 2.51 GHz) and stable broadside radiation patterns. The proposed antenna is suitable for multiband wireless communication applications as digital communication systems (DCS; 1710-1880 MHz), personal communication systems (PCS; 1850-1990 MHz), universal mobile telecommunication systems (UMTS; 1920-2170 MHz), and wireless local area networks (WLANs; 2.4-2.485 GHz).

Journal ArticleDOI
TL;DR: In this article, a narrow slot coupled to a microstrip line excites a DRA consisting of a small dielectric disc embedded in a larger disc is tested with two different slots providing eight different possibilities.
Abstract: A narrow slot coupled to a microstrip line excites a dielectric resonator antenna (DRA) consisting of a small dielectric disc embedded in a larger disc is built and tested. Two different configurations of DRAs are tested with two different slots providing eight different possibilities. One configuration provides a bandwidth over 50%. These antennas have broadside radiation patterns because of the symmetry presence of the slot with the DRA. Sample of radiation patterns are provided.

Journal ArticleDOI
TL;DR: In this paper, the properties of a long slot array fed by an array of periodically located feeds spaced at a Nyquist interval were investigated and the authors showed theoretically unlimited bandwidth when there is no backplane.
Abstract: This work deals with the properties of a long slot array fed by an array of periodically located feeds spaced at a Nyquist interval. The study begins with the rigorous Green's function (GF) of a single long slot which was extended to an infinite array structure. After this, the input impedance properties of the array when fed by an array of /spl delta/ sources are described by simple formulas, which explicitly show a theoretically unlimited bandwidth when there is no backplane.

Journal ArticleDOI
TL;DR: In this article, the effect of statistical parameters, viz. variance, and correlation length, on the focusing resolution of transmitted waves by the time-reversal (TR) array was investigated via numerical simulations employing the finite-difference time-domain (FDTD) method.
Abstract: We investigate superresolution effects on ultrawideband (UWB) electromagnetic waves (EM) produced by time-reversal (TR) arrays in continuous random media. The investigation is done via numerical simulations employing the finite-difference time-domain (FDTD) method. A Gaussian random background medium is considered. We compare the effect of statistical parameters, viz. variance, and correlation length, on the focusing resolution of transmitted waves by the TR array (TRA). The effect of depolarization is also briefly considered.

Journal ArticleDOI
TL;DR: An SVM-based approach for linear array processing and beamforming is introduced and the development of a modified cost function is presented and it is shown how it can be applied to the problem of linear beamforming.
Abstract: Support vector machines (SVMs) have improved generalization performance over other classical optimization techniques. Here, we introduce an SVM-based approach for linear array processing and beamforming. The development of a modified cost function is presented and it is shown how it can be applied to the problem of linear beamforming. Finally, comparison examples are included to show the validity of the new minimization approach.

Journal ArticleDOI
TL;DR: In this paper, a /spl plusmn/45/spl deg/ polarization diversity antenna with wide bandwidth is presented, which has a half-power beam width of 65 degrees in the horizontal plane for use in wireless telecommunication base stations.
Abstract: A /spl plusmn/45/spl deg/ polarization diversity antenna with wide bandwidth is presented in this letter. The antenna has a half-power beam width of 65/spl deg/ in the horizontal plane for use in wireless telecommunication base stations. Especially, a folded dipole antenna with a protruding part is used as a +45/spl deg/ polarization element and the another folded dipole with a concave part is used as a -45/spl deg/ polarization element. The protruding part and the concave part of dipoles make the two folded dipoles with the same height but not touching each other. With such a cross-pair of folded dipoles, a small polarization diversity antenna is constructed. The antenna was analyzed and optimized by the high frequency structure simulation software, and a good agreement was achieved between computation and experiments on the half-power beam width in the horizontal plane.