Compact CPW-Fed ultrawideband MIMO antenna using hexagonal ring monopole antenna elements

In this paper, a compact coplanar waveguide (CPW) fed ultra-wide band (UWB) multi input multi output (MIMO) antenna is proposed. The antenna consists of two antiparallel hexagonal ring monopole elements. Circular arcs shaped grounded stubs are used to enhance the isolation, both the arcs are connected through stub to make common ground. Tapering of the slots of CPW feed line at feed point, and grounded slots are introduced for impedance matching over UWB. The proposed antenna is fabricated and impedance bandwidth, isolation, radiation pattern, and gain are measured. Moreover, envelop correlation coefficient (ECC) results are given. Proposed antenna structure operates in the frequency range 3–12 GHz with a fractional bandwidth of 120% keeping isolation better than 15 dB. The antenna has a compact size of 45 × 25 mm².     

Base-station tracking in mobile communications using a switchedparasitic antenna array

Base-station tracking in mobile communications benefits from a directional antenna and so requires direction finding technology. A novel technique for electronically directing the radiation pattern of an antenna array employs a directional array with only one active element and three parasitic elements operating near resonance. Three different methods of direction finding are assessed; a coarse angular location method, a precise angular location method assuming one incident beam, and a precise angular location method with multiple incident beams. An array with n elements, if used in conjunction with a relatively simple controller, can be used to resolve n-1 signals. This technology can be implemented using both wire and patch antenna-array elements and either linear or circular polarization can be used, lending the technology to applications in both terrestrial and satellite communications systems     

带寄生单元宽带单极子天线研究

提出并设计了一种带寄生单元宽带单极子天线,该天线由一个单极子天线附加两个寄生振子组成.仿真及实验结果证明:天线在保持单极子天线特性的同时,实现了其宽带特性.该天线在750～2240 MHz的频带内反射损耗小于-10 dB,具有水平全向的方向图、稳定的增益.天线的结构和电特性决定了天线有广阔的应用前景,非常适用于移动通信终端设备,作为手持终端天线和车载天线将大有可为.     

Wideband CPW-fed monopole antenna with parasitic elements and slots

A novel compact and wideband coplanar waveguide(CPW)-fed monopole antenna is proposed. To increase the impedance bandwidth, two parasitic elements and three slots are added, which structures are optimised by a parametric analysis. The antenna operates over 3.1 to 11 GHz for the return loss of less than -10 dB. Radiation patterns also show very well omnidirectional performance of the proposed antenna.     

Radiation from a pulse-excited thin wire monopole

The physics of radiation is explored in the time domain by examining the behavior of a pulse-excited thin wire monopole antenna. The feed-point current, the charge and current densities along the wire, and the electric fields in the space around the monopole are first found in the frequency domain, using the method of moments and the wire surface boundary conditions. The Fourier transform is then used to find the time-domain behavior. The results support the notion that radiation comes from the feed point and the tip regions, and by direct calculation it is shown to be due to the integrated value of a distribution of the accelerated charge density. The behavior of the current at the feed point, and the charge and current densities along the monopole, are discussed in light of these results     

Dual-wideband monopole antenna using a modified half-sierpinski fractal gasket

A dual-wideband fractal monopole antenna for handheld terminals is proposed. A modified half-Sierpinski gasket patch is used to cover GPS, DCS1800, PCS1800, UMTS, IMT-2000, WiBro (Wireless Broadband Internet Service), Bluetooth, S-DMB (Satellite Digital Multimedia Broadcast) and WLAN bands. The proposed antenna exhibits two wideband frequency resonances. The measured -10-dB reflection bandwidths for two resonant frequencies are 55- (1517-2670-MHz) and 12.6- (5135-5828-MHz). The radiation characteristics and gain of the proposed antenna are also presented and discussed.     

Diversity gain for cdma systems equipped with antenna arrays

If the angular spread is not zero, the diversity gain can be achieved in the antenna-array reception. In order to achieve the diversity gain, we propose a beamforming method that utilizes two beamforming weight vectors and apply this beamforming technique to code-division multiple-access (CDMA) systems equipped with antenna arrays under a time-varying multipath-fading channel environment. In the proposed beamforming method, the channel vector has been estimated using two basis vectors that span the signal subspace. Since the proposed beamforming method utilizes two-dimensional (2D) signal subspace, it provides better performance than the conventional beamforming method, which utilizes one-dimensional signal subspace. Through simulation results, we can see that the performance is improved as the angular spread gets larger.     

A monopole antenna loaded with a modified folded dipole

A traveling-wave distribution of current can be produced on a linear antenna by inserting a resistance of suitable magnitude one-quarter wavelength from its end. In this study the resistor is replaced with a modified folded dipole which has a radiation resistance approximately equal to that of the matching resistor. Thus the input section has a traveling wave distribution up to the inserted antenna, as before, but now the power that was previously dissipated in the resistor is also radiated. Input impedance, current distribution, and radiation patterns of this antenna are computed, and input impedance and radiation patterns are also measured. Horizontally polarized patterns are similar to those of a horizontal dipole over a ground plane, and vertically polarized patterns in a plane orthogonal to the folded element are similar to those of a monopole over a ground plane. Coverage is also obtained in the zenith direction in the plane of the folded element, as long as it is not an integral number of half wavelengths above the ground plane. The peaks and nulls can be controlled by adjusting the monopole height accordingly and it is possible to achieve near hemispherical coverage     

Design of a multiband CPW-fed monopole antenna using a particle swarm optimization approach

A novel coplanar waveguide fed planar monopole antenna for multiband operation is presented in this paper. By embedding appropriate slits into the 50 /spl Omega/ feeding line, good impedance matching for multiresonant mode is obtained. The evolutionary design process of using a particle swarm optimization (PSO) algorithm in conjunction with the method of moments is employed to effectively obtain the geometry parameters of the antenna for optimum multiband performance. Prototypes of the obtained optimized design have been constructed and experimentally studied. The measured results explore good multiband operation with 10 dB impedance bandwidths of 55%, 8.5%, and 4.4% at bands of 2.51, 3.98, and 5.24 GHz, respectively, which cover the personal communication system and 2.4/5.2 GHz wireless local-area network operating bands, and show good agreement with the numerical prediction. Good monopole-like radiation patterns and antenna gains over the operating bands have also been observed. Effects of the patch size on the antenna performance and implementation of the physical PSO for the optimized configuration are all examined and discussed in detail.     

Bandwidth enhancement of the monopole antenna by using a parasitic normal-mode helix

An innovative monopole antenna coupled with a parasitic normal-mode helix has been designed and studied both experimentally and theoretically. The effects of various dimensions of the monopole and the parasitic helix were investigated extensively. This simple combination can significantly enhance the antenna bandwidth over that of the conventional monopole antenna. It is found that, with suitably chosen antenna dimensions, the VSWR bandwidth (VSWR ≤ 2) of the antenna can be increased to 36%, almost double that of the monopole antenna alone. The far-field pattern of the combined antenna is basically the same as that of the monopole antenna. This antenna is designed to operate at 1.8GHz. The substantially enhanced bandwidth of this simple and small antenna is a useful feature for future mobile communications.     

一种超宽带地板开槽单极子天线的设计

研制了一款超宽带印刷单极子天线。通过在接地板和单极子贴片底部开槽,展宽了天线频带,改善了天线带内特性,提高了天线增益。采用HFSS软件进行仿真,对天线模型参数进行优化,达到最佳设计效果。结果表明,改进后的天线-10 dB阻抗带宽为2.2~14.6 GHz,比原不开槽天线的-10 dB阻抗带宽增加了7.2 GHz。天线实现了小型化超宽带的同时,在整个超宽带匹配频段内,具有良好的驻波和方向图特性,在超宽带设备中有着很好的应用前景。     

Scattering from a wire antenna/hemisphere structure

The electromagnetic scattering from a grounded wire antenna/hemisphere structure is analysed using the mode matching method as well as the method of moments. The influence of the conducting hemisphere on the radar cross-section of a wire antenna is taken into account. Some numerical results are given     

一种新型超宽带单极子天线设计与仿真

通过单极子和高介电常数(相对介电常数为38)陶瓷介质谐振器的耦合设计了一种新型类齿状UWB单极子天线,以实现天线超宽频带的目的。采用软件HFSS进行仿真,并对天线模型参数进行优化,得到最佳设计效果。结果表明,该天线频带宽度为2.6~20.0 GHz(S11≤–10 dB),相对带宽达到了154%,满足超宽带天线要求。该天线实现小型化超宽带的同时,在整个UWB匹配频段内,具有良好的驻波比和方向图特性,较好地兼顾了各方面的性能。     

基于矩量法对导体板上单极天线特性研究

利用矩量法对有限大导体板上单极天线的阻抗特性进行了研究。基于Pocklington积分方程和Galerkin法，采用分域基正弦函数展开模式，得出了有限尺寸导体板上单极天线的电流分布和输入阻抗，并对单极天线在不同长度及不同导体板上的情况进行了研究。结果表明，单极天线的长度及导体板的形状及大小在一定程度上影响了单极天线的特性。     

Sierpinski monopole antenna with controlled band spacing and inputimpedance

A novel configuration of the Sierpinski triangular gasket antenna is proposed. A quasi-log-periodic performance was achieved for the operating bands of GSM, DECT and WLAN by using a new band spacing control technique. This design enhances the input matching performance to well over -10 dB with a 50 Ω feed     

Ultrawide-band square planar metal-plate monopole antenna with a trident-shaped feeding strip

A square planar metal-plate monopole antenna fed by using a novel trident-shaped feeding strip is presented. With the use of the proposed feeding strip, the square planar monopole antenna studied shows a very wide impedance bandwidth of about 10 GHz (about 1.4-11.4 GHz, bandwidth ratio about 1:8.3), which is larger than three times the bandwidth obtained using a simple feeding strip (about 1.5-3.3 GHz, bandwidth ratio about 1:2.3). In addition, the proposed feeding strip can be integrated with the square planar monopole, that is, the feeding strip and the square planar monopole together can be easily fabricated using a single metal plate, making the proposed antenna easy to construct at a low cost. Details of the experimental and simulation results for the proposed planar monopole antenna are presented and analyzed.     

Equivalent circuit of a dipole antenna using frequency-independentlumped elements

A four-element lumped-parameter equivalent circuit, consisting of a resistance, an inductance, and two capacitances, has been found to represent the feed-point impedance of a dipole antenna. The values of these elements are related only to the physical dimensions of the antenna, not the frequency of operation. Empirical formulas are given for all the elements. The equivalent circuit gives negligible errors in radiation resistance and reactance for dipole half-lengths less than 0.1λ, rising to 1% for resistance and 6% for reactance at 0.25λ. It can be readily used in standard computer software packages such as SPICE, PSPICE, and MICROCAP     

Design of an ultra wide-band printed monopole antenna using FDTD and genetic algorithm

This letter presents an ultra wide-band (UWB) antenna with a printed monopole structure fed by a coplanar waveguide (CPW) line. The antenna is analyzed by using the finite-difference time-domain (FDTD) method and genetic algorithm (GA) to achieve an ultra wide bandwidth characteristic. The measured frequency response shows an impedance bandwidth of 7.25GHz or 104.7% over 3.3 to 10.55GHz for VSWR less than 2.     

A circular monopole antenna for bandwidth enhancement using cylinder slots with triple band notch characteristics

This article introduces a super wideband along with three notch bands circular patch monopole antenna. The design structure is applicable for microwave and high-speed wireless devices (2.19 to 25 GHz). In order to create a broad band, a ring dimension circular patch is used. To generate three notch bands, six symmetrical tiny cylinder stubs are introduced on the ground. These notch band frequencies can eliminate unwanted interference from various wireless frequencies, which mainly cover three notch bands: 5.5–7.3, 12.05–14.46, and 17.71–19.5 GHz. The steady radiation, super bandwidth, and stable gain properties expand when the ring patch and line feed are combined. It is excellent for many UWB applications because of its compact size (39 × 29 mm ²) and large bandwidth (166.97% fractional bandwidth). This model employs various size reduction and matching approaches to get a better response. The mechanisms of these structures are identified, and overall performance is compared with parametric analysis, tables, and figure.     

The signal produced in a monopole antenna by the gamma flux from a nuclear explosion

A monopole antenna is considered to be bombarded by a flux of gamma rays propagating normally to the axis of the antenna. As a result of this bombardment, electrons are scattered from the antenna, thus charging the antenna positively. This induces a current in the load impedance of the antenna-appearing as if the antenna were receiving a transient RF signal. An expression for the time dependent voltage across the load impedance of the antenna is obtained by considering that every electron scattered from the antenna never returns and that the antenna impedance and capacitance are their free-space values.