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A new antenna with dual-band circular polarization for the reception of WiMAX and WLAN is presented in this article. The circular polarization is achieved by a symmetrical U-slot together with an L-slot. The width of the signal strip is narrowed at the end of the feed point to widen the 3-dB axial ratio (AR) bandwidth and create a good impedance matching for the proposed antenna. A parametric study is conducted using a commercial simulation software based on the method of moments, and the antenna prototype is constructed and measured for providing the simulation validation. Experimental results show that the measured AR bandwidths are about 16.6% and 16.2% with respect to the center frequency at 3.5 GHz and 5.3 GHz. The radiation characteristics of the proposed antenna are also presented. [ABSTRACT FROM AUTHOR]

A novel broadband monopole antenna design with wideband circular polarization (CP) characteristic is presented. This antenna consists of a feed line and a step-shaped ground plane which is formed by cutting a notch in the upper left corner of an asymmetric ground plane. The asymmetric ground plane is capable of exciting two orthogonal electric field vectors with equal amplitude and 90° phase difference (PD) for CP. By cutting a notch, the 10-dB impedance-bandwidth can be enhanced greatly and the 3-dB axial ratio (AR) bandwidth is also improved meanwhile. The measured impedance- bandwidth is about 5.96 GHz (84.7%) from 4.06 to 10.02 GHz, and the measured AR-bandwidth is about 2.64 GHz (36.5%) from 5.91 to 8.55 GHz. The results show that the antenna can achieve wide impedance-bandwidth and wide AR-bandwidth simultaneously. [ABSTRACT FROM AUTHOR]

In this paper, a covariance matrix adaptation evolutionary strategy (CMA-ES) is employed for optimization design of non-uniform circular antenna arrays. To achieve minimum sidelobe levels with the constraint of a specific first null beamwidth, the CMA-ES is utilized to find out the optimal weights and geometry of the circular array. The three various circular ring arrays are solved via CMA-ES, and the results are presented for arrays of varying configurations. The design results obtained with CMA-ES are compared to the existing array designs in the literature and to those found by the other evolutionary algorithms. Comparison with the results of other algorithms reveals the superiority of the CMA-ES. [ABSTRACT FROM AUTHOR]

A simple ultra-wideband planar rectangular printed monopole antenna with dual narrow band-notched characteristics is presented in this paper. Dual narrow band-notched frequencies at 3.4 GHz and 5.2 GHz are achieved by embedding a U-shaped slot in the radiation patch and a small pentagon patch on the ground, respectively. Moreover, input impedance, conceptual equivalent circuit models and surface current distributions are built for analysis and explanation of dual narrow band-notched characteristics. At the same time, an approximate expression of the notched frequency with the pentagon patch dimension is proposed in this paper. The designed antenna operates over the frequency band between 2.69 GHz and 12 GHz (126.8%), with one narrow notched band from 3.32 GHz to 3.55 GHz (6.7%) and the other from 5.04 GHz to 5.39 GHz (6.8%). The antenna is successfully simulated, fabricated and measured, showing broadband matched impedance, dual narrow band-notched characteristics, stable gain, high radiation efficiency and omni directional radiation patterns. [ABSTRACT FROM AUTHOR]

A compact ultra-wideband (UWB) slot antenna based on a mesh-grid structure is designed. A Boolean differential evolution (BDE) algorithm is used to optimize the mesh-grid structure as well as other parameters of the proposed antenna for good impedance matching in the UWB band. The optimized UWB antenna has a compact size of 24.2mm x 32.2mm and is fabricated and measured. According to the measured results, the proposed antenna yields a wide bandwidth, defined by S11 < -10 dB ranging from 2.8 to 11.2GHz. And it shows that the BDE algorithm is an e?ective method for antenna design. [ABSTRACT FROM AUTHOR]

A novel RCS (radar cross section) reduction configuration for a reflectarray antenna, employing the appropriate FSS (frequency-selective surface) as a ground, is proposed. The performance of a reflectarray element backed either by a solid metal ground plane or a frequency-selective surface is compared. To optimize the performance of the designed frequency-selective surface, a parametric study is carried out using Ansoft HFSS. Then, a prime-focus FSS-backed reflectarray is fabricated and tested. The measurements demonstrate that the gain of a FSS-backed reflectarray is about 0.5 dB lower than its counterpart backed by a solid ground plane. The RCS is nearly the same at the operating band of 10GHz, while out of this band the FSS-backed reflectarray reduces the RCS strongly, especially at 1GHz with the reduction up to 20 dB. Compared with the RCS reductions obtained in the other papers, the FSS-backed reflectarray using a ring element can also obtain a good result. [ABSTRACT FROM AUTHOR]

A novel coplanar waveguide (CPW) fed wide tapered slot antenna (WTSA) is presented in this paper. A wideband CPW-to-wide slotline (WSL) transition is employed to feed the antenna. The corrugated edge structure and broken line tapered profile are also applied in this design to achieve wideband performance, as well as maintain compact size. A prototype of the antenna is fabricated. The measured results indicate that the antenna is a good candidate for UWB detection and imaging applications. [ABSTRACT FROM AUTHOR]

In this paper, we propose a computational global optimization method based on differential evolution (DE) algorithm for synthesizing large multiple concentric rings arrays to generate a pencil beam with minimum peak side lobe level (PSLL) and constrained first null beam width (FNBW). The synthesis is performed with a differential evolution technique to optimize the ring spacing, the number of the elements in each ring as well as the amplitude distribution. Simulated results of the designed synthesis illustrate the efficiency and reliability of our proposed method. [ABSTRACT FROM AUTHOR]

A novel compact multiple-input multiple-output (MIMO) antenna using a ring hybrid is proposed in this paper. The proposed antenna is designed for the 2.4 GHz Wireless Local Area Network (WLAN) applications. A ring hybrid of arbitrary power division is designed as the orthogonal feeding network to improve the isolation between the ports of the two monopoles. Two meander-line monopoles are used to miniature the proposed antenna. The prototype antennas have been evaluated and compared through the scattering parameters, radiation patterns. The results show that the isolation between the ports of the proposed antenna is better than 23 dB with matched ports at 2.4 GHz. The size of the proposed antenna has also been reduced by 15.7%. The proposed antenna offers reasonable WLAN performances that make it suitable for MIMO applications. [ABSTRACT FROM AUTHOR]

As a very powerful optimisation approach, differential evolution algorithm for continuous optimisation problems has been applied to electromagnetic (EM) design problems. However, the optimisation of a thinned array can be formulated as a discrete-variable optimisation problem with solutions encoded as binary strings. Here, a Boolean differential evolution (BDE) algorithm for 0-1 integer programming problems is proposed to design planar thinned arrays with minimum sidelobe levels. The BDE algorithm with only one control parameter is easily implemented. Meanwhile, a fast Fourier transform is employed to speed up the calculation of the pattern. Numerical experiments show that the BDE algorithm is an effective technique. [ABSTRACT FROM AUTHOR]

In this article, a simple and compact CPW-fed planar monopole antenna for ultra-wideband applications is presented and investigated.The proposed antenna with a small size of 26 mm × 26 mm × 1 mm is composed of a gourd-like radiation element fed by a CPW feed line, and a modified stair-style ground. The proposed antenna has been successfully designed, fabricated, and measured. The measured results show that the antenna achieves a wide impendence bandwidth from 3.1 to 15.2 GHz with return loss less than -10 dB. In addition, it exhibits a nearly omnidirectional radiation pattern, stable antenna gain, and good time-domain characteristics across the operation band. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2100–2104, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.25378 [ABSTRACT FROM AUTHOR]

A novel high gain circularly polarized antenna using sub-wavelength resonant cavity is presented. The resonant cavity consists of a single partially reflective surface (PRS) and an artificial impedance surface (AIS). By adjusting reflection phases of the PRS and AIS at the operating frequency, the cavity height that is the distance between these two reflectors can be reduced to about λ/8. The measured results show that this method is effective, and this structure can greatly increase the circular polarization gain of the antenna. [ABSTRACT FROM AUTHOR]

In this article, a planar monopole antenna with dual band-notched characteristics for ultra-wideband (UWB) applications is presented. By embedding a pair of L-shaped arc slots into the radiation patch and adding a pair of C-shaped resonators to the microstrip feed line, the 3.5/5.5 GHz dual band-notched characteristics are achieved, respectively. The proposed antenna was successfully simulated, fabricated and measured. The simulated results agree reasonably with the measured ones, showing that the proposed antenna provides an operating band ranging from 2.4 to 12.4 GHz with VSWR less than 2.0, except the frequency bands of 3.2 ∼ 3.8 GHz and 5.1 ∼ 6.0 GHz. In addition, the proposed antenna exhibits a nearly omnidirectional radiation pattern in the H-plane and stable gain across the entire operating band. The detailed design and experimental results are discussed in this article. [ABSTRACT FROM AUTHOR]

The design and analysis of a printed UWB antenna with multiple band-notched characteristics are presented in this paper. The proposed antenna consists of a fork-shaped radiation element on the front side and a modified rectangular slot on the ground plane. By inserting three different novel resonating structures (curl slotline, zigzag open stub and C-shaped resonator) in the reference UWB antenna, multiple band-notched characteristics at 2.4 GHz, 3.5 GHz, 5.8 GHz are achieved. Good agreement between simulation data and measurement results is obtained. And the measured peak gain of the proposed antenna is shown in this paper. The results prove that this antenna can be applied to the UWB communication systems to avoid interference with other narrowband wireless systems, such as 2.4 GHz WLAN, 3.5 GHz WiMAX, and 5.8 GHz WLAN. The conceptual equivalent circuit models, which are based on the surface current distributions on the resonating structures, are also shown to further analyze the band-notched characteristics. [ABSTRACT FROM AUTHOR]

In this article, a compact ultra-wideband monopole antenna with dual band-notched characteristic is proposed, in which the C-shaped slot creates one band-notch at 3.5 GHz, and the pair of inverted-L-shaped slots produce another band-notch at 5.8 GHz. Simulated and measured results show that the operating frequency band (VSWR < 2) of the proposed antenna is from 2.7 to 11.5 GHz, with the dual bands of 3.3–3.7 GHz and 5.5–6.4 GHz notched. By changing the lengths of the C-shaped slot and the pair of inverted-L-shaped slots, the central frequencies of the dual notched bands can be adjusted easily. [ABSTRACT FROM AUTHOR]

In this article, a new design of a broadband dual circularly polarized square slot antenna loaded with metallic strips is presented. The proposed dual circular polarization (CP) radiations are achieved by loading the square slot with a T-shaped strip and two microstrip T-junctions. The designed antenna is implemented and measured. The experimental results show that the proposed antenna has good dual CP characteristics and a 3-dB axial ratio bandwidth is more than 19%. The isolation between two ports is better than 20 dB within the CP operating band. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2639–2642, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23741 [ABSTRACT FROM AUTHOR]

A novel reconfigurable annular ring-slot antenna with switchable polarization is presented. Circular polarization (CP) radiation of the proposed antenna is obtained by introducing protruded slots and strips in the annular ring-slot structure. Two diodes are used to reconfigure the structure of the annular ring-slot. Switching between right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) is achieved by turning the pin diodes on or off. The proposed antenna has simple structure and can be controlled easily. An antenna prototype is implemented and the measured results are shown. [ABSTRACT FROM AUTHOR]

In this paper, a broadband CPW-fed slot antenna with a gradual-changed ground plane for bandwidth enhancement is proposed and experimentally studied. The effect of various shapes of the slot on broadband operation is investigated. From the experimental results, the measured impedance bandwidth, defined by 10 dB return loss, could be as large as 3.75 GHz or about 105% centered at about 3.56 GHz. The antenna radiation patterns within the operation band were also measured and studied. [ABSTRACT FROM AUTHOR]

A novel double H-shaped slot is introduced to achieve a dual-band coplanar waveguide CPW-fed antenna for radio frequency identification (RFID) applications. The designed antenna is low in profile and can operate simultaneously at 2.45 and 5.8 GHz bands with 1.07 and 2.38 dBi gains, respectively. Also, good omnidirectional radiation patterns have been obtained. Its properties make the antenna not only suitable for RFID tags, but also for WLAN applications. [ABSTRACT FROM AUTHOR]

A new method to improve the gain of patch antenna with metamaterial composed of ring aperture lattice spaced periodically along two arbitrary vectors is presented. The properties of the metamaterial are discussed, and the effective index of refraction and effective permittivity can be retrieved at all frequencies. Then a patch antenna with metamaterial is fabricated and measured. The experimental results show that this method is effective and this structure can realize congregating the radiation energy, thus the gains of the patch antenna with metamaterial can be greatly increased compared with the conventional one. [ABSTRACT FROM AUTHOR]

In this paper, a novel CPW-fed dual folded-strip monopole antenna with a pair of inverted L-shaped stubs is proposed for multiband applications. Reasonably large impedance matching bandwidth and good omni-directional radiation patterns have been observed. The measured impedance bandwidths reach about 27% for the lower band and 32% for the higher band, which meets the required bandwidth specifications of 2.4 GHz WLAN, 2.5 GHz WiMAX, DMB and 5.2/5.8 GHz WLAN standards. The proposed antenna with relatively low profile is suitable for multiband wireless communication systems. [ABSTRACT FROM AUTHOR]

A compact ultra-wideband (UWB) microstrip-fed planar monopole antenna with the band-notched characteristic is presented. This antenna comprises an annular-shape radiating element and a tuning stub which is inserted into the annular structure to obtain the band-notched characteristic. The notch frequency can be easily adjusted from 5 to 6.3 GHz by tuning the length of the stub. The VSWR characteristic from (3–24 GHz) and quasi omni-directional radiation pattern is observed. The proposed antenna is suitable for all UWB communication applications and prevents interference with the WLAN systems. [ABSTRACT FROM AUTHOR]

A conformal array antenna composed of 8 low-profile Eshaped patches mounted on an irregular shaped surface is designed for 360° coverage in the horizontal plane. Unequal thickness substrate is used in the conformal low-profile E-shaped patch design to maintain the wide-band characteristic of the conformal E-shaped patch antenna. Fitness distance ratio (FDR) based particle swarm optimization (PSO) is used to synthesize the patterns of the conformal array. Good agreement is observed between numerical and experimental results of the conformal array antenna. [ABSTRACT FROM AUTHOR]

This paper presents a novel technique to change the impedance characteristics of patch antenna to achieve multi-band. The proposed structure is based on the metamaterial concept. By replacing the conventional substrate of patch antenna with metamaterial, the impedance characteristics can be effectively changed to produce multi-band property. The design is based on the dispersive characteristic of the substrate by using metamaterial structure. To validate the proposed approach, numerical and experimental results are presented; the results show the validity of our approach. [ABSTRACT FROM AUTHOR]

An interpolation method for the approximation of three-dimensional (3-D) antenna radiation patterns from two cuts (vertical and horizontal) is presented in this paper. The absolute error for the proposed approximation method from the simulation results is analyzed for various types of antenna structures, including omni-directional and directive antennas. The performance of the method is compared against other existing extrapolation algorithms. The proposed method exhibits low approximation errors. [ABSTRACT FROM AUTHOR]

An evolutionary optimization method for patch antenna designs is presented in this paper. The modified particle swarm optimization (MPSO) based on fitness distance ratio (FDR) is combined with standard software IE3D to achieve the optimum antenna satisfying a certain design criterion. The antenna geometric parameters are extracted and optimized by a MPSO program, and simulated by IE3D. The fitness function of the optimization is calculated by the MPSO program according to the simulation results extracted from IE3D to represent the performance of each candidate design. A microstrip line fed low-profile E-shaped patch antenna is designed and optimized using the MPSO/IE3D method. The designed patch antenna is simulated, fabricated, and measured to validate the effectiveness of the MPSO/IE3D method. [ABSTRACT FROM AUTHOR]

A novel reconfigurable coplanar waveguide (CPW)-fed square slot antenna with switchable polarization is presented. The proposed antenna is fed by a CPW, with two T-shaped metal strips connected to ground plane using pin-diodes. Switching between right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) is achieved by turning the pin-diodes on or off. The designed antenna is implemented and measured. It shows that the proposed antenna has broad CP bandwidth in both RHCP and LHCP states. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1233–1236, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22476 [ABSTRACT FROM AUTHOR]

A compact structure is proposed to realize dual circularly polarized antenna for RFID system. In this paper, a cross-shaped aperture in the ground plane provides coupling between the patch and a single microstrip line with two ports underneath the ground plane, the means of feeding is constructed. For system requirements, some modifications are made to improve the performance. This design realizes low profile, separating the radiating patch and the feeding layer, particularly saving space by avoiding the traditional scheme based on microstrip branch line coupler. In the wireless communication system for RFID applications, circular polarization modulation (CPM) is implemented, which reduces the requirement for bandwidth effectively, and simplifies the data communication. Therefore, a dual circularly polarized antenna is an indispensable key part of this RFID system, and in some case the compact structure is necessary. In this design process, the dimensions and performance of this antenna are calculated and optimized by HFSS (High Frequency Structure Simulator). The results agree well with the measurement, and show the practicability of this scheme. [ABSTRACT FROM AUTHOR]

A new reflector shaping technique to improve the beam scanning capability of hybrid antennas (i.e., a reflector system illuminated by a phased array) is presented. Errors between the desired scan directions and the outgoing rays' directions in the scanning range are minimized by adjusting the reflector shape. This technique can be used to decrease the active element number of the feed array during the antenna scans, or reduce the gain loss caused by beam scanning when the number of active elements is given. An offset reflector antenna system is designed and analyzed, through which the validity of the technique is demonstrated. [ABSTRACT FROM AUTHOR]

A novel CPW-fed broadband circularly polarised square slot antenna is proposed and fabricated. The proposed antenna is fed by a CPW with a widened L-type strip along the diagonal line of the square slot. Measured results show that the 3 dB axial-ratio bandwidth of the proposed antenna can reach 17%. The proposed antenna has simple coplanar geometry which can be easily fabricated on inexpensive substrate. [ABSTRACT FROM AUTHOR]

A 5.2 GHz band-notched ultra-wideband monopole antenna using a proximity coupled resonator is proposed. Compared with conventional methods which transform antenna/ground structures to achieve band-notches, the proposed monopole antenna uses a coupled resonator to obtain a band-notch at 5.2 GHz and does not change the antenna surface current distribution. Two layer substrates are used and the resonator is placed between the feed line and the ground plane. An experimental prototype was fabricated and the measured data display an impedance bandwidth of 2.5–11 GHz with VSWR<2 except for the rejected band of 5.06–5.52 GHz for HIPERLAN application. Also, near-omnidirectional radiation characteristics in the desired frequency band can be obtained. [ABSTRACT FROM AUTHOR]