An improvement of parasitic dipole array using suppressor elements

A novel configuration of parasitic arrays is introduced. The characteristics of the array in both forward and backward radiation are improved by using a new element, the suppressor. The suppressor elements are aligned parallel to a radiating dipole or to a conventional endfire array such as a Yagi-Uda array. Radiation in the unwanted direction is reduced by the suppressors, and the forward gain is effectively increased. Design of the optimum antenna parameters was achieved using the moment method, and results were compared to measured values, with good agreement obtained. New arrays were compared to well-designed Yagi-Uda arrays. A new array which is aligned with two broadside suppressors and with three endfire elements had an improved forward gain of 1.5 dB and a reduced backward gain of -4 dB compared to a conventional, well designed Yagi-Uda array with five endfire elements     

Cross-spectral densities of array elements for folded dipole and loop antennas

When a loop or folded dipole antenna is placed in a noise field the resultant mean-square noise current is a function of the cross-spectral densities between the different segments of the antenna. Earlier work on the evaluation of cross-spectral densities between the collinear segments of a dipole placed in an isotropic noise field is here extended to include the parallel and orthogonal segments of rectangular loop and folded dipole antennas.     

A network model of a feedthrough phased array lens of printed dipole elements

An easy-to-use simplified network representation for the internal multiple reflection model of feedthrough phased array lens antenna elements is presented. This model makes use of the readily known active radiation impedances of an infinite array rather than the self and mutual impedances between array elements. In particular, this model is applied to a printed dipole lens array case, for which the computation of the radiation impedance is described. Numerical results for this lens array are given to show the aperture distribution variations due to the lens internal multiple reflection, and the gain falloff as a function of scan angle.     

Infinite phased dipole array

By means of a Poisson sum formula and an integral-equation technique, an accurate solution for an infinite phased dipole array is obtained. The elements of the array are spaced uniformly and are excited with increasing phases. The technique can be applied to an infinite collinear array and to an infinite planar array either in free space or over a ground plane. The integral equation is solved both by a Fourier method and by an approximate five-term procedure. It is found that the latter is as good as the former. The current distributions and the active admittances are investigated.     

Monopulse printed circuit dipole array

The design and performance of a monopulse Ku-band planar array is described. The antenna is designed to provide 20 dB sidelobes sum pattern in the azimuth plane and an operating bandwidth of 1 GHz (16.25-17.25 GHz). The voltage standing-wave ratio (VSWR) of this array at the input is less than 2:1 over the bandwidth.     

Steered coupled-cavity-backed Hertzian dipole array

This paper presents the operating characteristics of a coupled-cavity-backed Hertzian dipole resonator array excited with mutually injection-locked voltage-controlled oscillators (VCOs). It is demonstrated that microwave spatial power-combined inter-injection locking through mutual coupling of individual antenna oscillators can be obtained with an auxiliary coupling network formed by a cavity iris configuration introduced within a reduced-height waveguide arrangement. As a result, strong mutual-coupling control can be realized and exploited in conjunction with self-injection-locked oscillators in order to achieve direct phase modulation of the locked oscillators. Beam scanning up to 10° off the broadside through locked VCO phase modification has been demonstrated in a three-element array occupying a space of only 0.6 λ₀×0.027 λ_o at 998 MHz     

Very wideband printed dipole antenna array

The design and experimental results of a very wideband small printed dipole antenna array are presented. The impedance bandwidth (VSWR ⩽1.7) of the antenna, centred at 780 MHz, is 47%. In the frequency band 610-960 MHz, the designed antenna has a gain of 9.5-11.9 dBi, sidelobe level <-16 dB and front-to-back ratio <30 dB. The main features of the design are the use of parasitic elements to expand the frequency band and the application of a mesh frame to decrease the sidelobe level     

Electromagnetically coupled coaxial dipole array antenna

A new type of collinear antenna called electromagnetically coupled coaxial dipole array antenna is proposed. The antenna has an advantage of structural simplicity due to a novel use of an electromagnetically coupled feed structure for the radiating element. An analysis of the radiating element is presented and compared with experimental results. Fabrication and measurement of a prototype array antenna are also presented     

Backfire antennas with dipole elements

A method is set up for a theoretical investigation of arbitrary backfire antennas based upon dipole structures. The mutual impedance between the dipole elements of the antenna is taken into account, and the field radiated due to a surface wave reflector of finite extent is determined by calculating the surface current distribution on the reflector plate. Numerical results obtained for Yagi backfire antennas and short-backfire antennas using this theory are compared with experimental results.     

一种水平全向平面偶极子阵列天线

基于偶极子组阵结构,设计了一种具有水平全向辐射方向图和水平极化特性的平面天线。该天线由3只偶极子天线组成,每只振子弯折30°并上下交错印刷在PCB板的表面上,构成正六边形环,环的直径为0.45λ0(λ0为中心频率处的自由空间波长)。3只偶极子天线均采用SMA接头直接顶馈,从而省略了偶极子天线的馈电巴伦。通过优化偶极子天线振子长度和间距等结构参数,以及控制馈电相位,实现水平全向辐射。设计和加工制作了一只工作频率为2.45 GHz的天线样品,测试与仿真结果吻合良好,其|S11|≤10 dB的相对阻抗带宽为12.94%(2.367~2.684 GHz),水平全向增益约为1.42 dBi,不圆度小于±0.7 dB。     

Loop coupling to a periodic dipole array

Conditions are found experimentally for optimising the coupling between a looped feeder (transposed transmission line) and a log-periodic array of radiating dipoles. Under optimum conditions, the coupling is sufficient to be useful in practical antennas.     

ANALYSIS OF DIPOLE AND DIPOLE ARRAY BY A COLLOCATION TECHNIQUE WITH MULTIPOINT WEIGHTING

A collocation method with multipoint weighting is presented in this paper.Itconverges as rapidly as the Galerkin method hut needs less computation effort.By means ofthe technique with Gauss points(superconvergence points)as the collocating points,dipole anddipole array are analyzed,and the numerical results are in good agreement with those given inrelative references.     

对数周期曲线振子天线的分析与设计

对数周期天线小型化的一种途径是利用新的谐振天线(如V型天线、螺旋天线、分形天线等)代替半波振子来降低谐振高度,这些对数周期天线可以统称为对数周期曲线振子天线.利用基于Nakano方程的矩量法结合等效电路理论来分析对数周期曲线振子天线的新方法,并对几种小型化的对数周期天线进行了研究.计算机仿真表明:该算法简单易行,为研究新型结构的对数周期天线和对数周期天线的小型化提供了一种新途径.     

GA optimisation of crossed dipole FSS array geometry

Crossed dipoles are used as dual polarised elements in frequency selective surface arrays but the transmission response is angle of incidence dependent. A genetic algorithm has been used to minimise the drift of the reflection band, stabilising it for a wide range of angles, to beyond 60°, even on thin substrates     

Analysis of an infinite phased array of dipole elements with RAMcoating on ground plane and covered with layered radome

An analysis of an infinite array of dipole elements over a radar absorbing material (RAM) coated ground plane and covered with a radome is presented. The radiation impedance of the dipole element is obtained when the array is in transmitting mode, and a scattering analysis is carried out when the array is excited by an incoming plane wave and the dipole elements are terminated in loads. The electric field Green's function in terms of Floquet mode expansion due to a periodic δ-function horizontal dipole source is derived to satisfy the layered boundary conditions. The method of moments is used to solve the current distribution on the dipole. Numerical calculation of the radiation impedance of a dipole array covered with a radome has been verified with results from waveguide simulator measurements. Numerical examples are given to show the effect of the RAM coated ground plane on the radiation impedance and the scattering characteristics     

Opened parasitic elements nearby a driven dipole

The characteristics of an antenna system consisting of opened parasitic elements and a nearby parallel driven dipole antenna are investigated. The aim is to show quantitatively the significance of the opened parasitic elements that affect the characteristics of the antenna system, and hence cannot be ignored as the radius of the elements becomes thick and the interelement spacing becomes small.     

Ridged waveguide phased array elements

The mutual coupling solution of dual and quad ridged waveguide is described for an infinite array environment. The method of analysis is the numerical solution of integral equations for both the eigen solution and the boundary matching problem. In addition to numerical results, comparison of theory with waveguide simulator measurements is also given.     

Analysis and design of a leaky-wave EMC dipole array

An analysis of an electromagnetically coupled (EMC) dipole array is presented, in which a microstrip line is coupled to an infinite periodic linear array of microstrip dipoles, arranged perpendicular to the line. The spectral-domain immittance method is used to obtain the periodic Green's function for the two-layered structure, and the method of moments with a Galerkin testing procedure is then used to enforce the electric field integral equation (EFIE) on the line and the dipole within a unit cell of the structure to obtain the determinantal equation for the unknown leaky-wave propagation constant. One of the interesting features of this analysis is the path of integration in the complex plane used to compute the moment method reactions, which must be partly on the improper sheet for the m=-1 space harmonic when it radiates in the forward direction. Measured radiation patterns for a 10-element EMC dipole array are presented and compared with the corresponding theoretical ones