Single-feed dual-band circularly polarised microstrip antenna

A novel technique for obtaining dual-band circular polarisation (CP) radiation of a single-feed circular microstrip antenna is proposed and demonstrated. By embedding two pairs of arc-shaped slots of proper lengths close to the boundary of a circular patch, and protruding one of the arc-shaped slots with a narrow slot, the circular microstrip antenna can perform dual-band CP radiation using a single probe feed. Details of the antenna design and experimental results are presented     

Near Field Analysis of the Modal Scattering at Radiating Apertures

A rigorous method for the determination of the modal scattering at radiating apertures is presented. Near-field boundary conditions to be satisfied on the outer surface of the conducting structure containing the aperture (e.g. a horn antenna) are completely taken into account. The resulting scattering matrix of the radiating aperture can be integrated into any mode-matching technique as a termination for the cascaded structure commonly used to match the aperture to the exciting waveguide. The method is based on a multiple-multipole expansion of the electromagnetic field outside the radiating object in conjunction with a point-matching technique. Horn antennas with elliptical and circular apertures have been analyzed using the suggested method. Excellent agreement with measurement results has been achieved for both the radiation pattern and the aperture scattering parameters.     

FDTD technique for modelling eight-element circular antenna array

An eight-element circular antenna array consisting of an eight wire monopole mounted on a circular ground plane is modelled using the finite-difference time-domain (FDTD) method. Examples of frequency response as well as the far-field radiation pattern are presented. Comparisons against measured responses of the actual array show that the FDTD method provides an accurate model of the antenna array.     

小横向尺寸的圆弧振子背射天线

本文叙述了一种横向尺寸很小的(近似等于0.5)圆弧振于背射天线。文中介绍了它的结构和实验结果。实验结果表明,该天线仍具有较好的电气性能。     

Circular polarisation design of a single-feedequilateral-triangular microstrip antenna

By inserting a narrow slit at the edge of an equilateral-triangular microstrip patch, circular polarisation (CP) radiation can be obtained using a single probe feed. This CP design is easy to implement. Details of the antenna design are described, and experimental results of the axial ratio and radiation pattern are presented and analysed     

Circularly polarised planar antenna excited by coplanar waveguide feedline

A circular patch antenna fed by a coplanar waveguide (CPW) line is proposed to obtain circular polarisation (CP). The CP results from the combined excitation of the patch by an inclined slot (integrated in the CPW feedline) and the CPW feedline termination. The asymmetrical characteristics of the excitation involve the excitation of both the odd and the even modes in the CPW line.     

喷管类型对飞行器排气系统辐射特性的影响

排气系统是飞行器最主要的红外辐射源,其喷管的形状类型对排气系统红外辐射强度的大小及分布有很大影响.本文建立了3种不同类型喷管的三维模型,在此基础上运用ANSYS软件模拟了各自排气系统的温度场分布,结合Curtis-Godson(C-G)谱带法对各类型喷管红外辐射特性进行了计算与对比研究.结果表明:在出口面积相同的条件下...     

基于矩量法的螺旋天线设计

螺旋天线具有宽波束、圆极化等特性。以往的轴向螺旋天线多为端射式,辐射方向单一。为弥补这一不足,提出了一种新型的中馈轴向螺旋天线。基于RWG(Rao-Wihon-Glisson)边元的矩量法,采用MATLAB仿真计算出中馈螺旋天线的方向图、反射系数、增益等重要参数。又利用高频结构仿真软件(HFSS)对所设计的中馈螺旋天线进行了仿真。通过两种方法仿真得到的结果吻合较好,仿真结果的正确性得到了验证。实验结果表明:中馈轴向螺旋天线不仅具有以往轴向螺旋天线所具备的定向性好和高增益等优点,还具有两个反向且强度相同的辐射方向,同时天线增益可以达到8dB以上,半功率波束宽度可达33°。这种天线可以应用到多边通信及中继通信等领域。     

Radiation pattern synthesis for circular aperture horn antennas

A set of radiation pattern functions, suitable for synthesis of radiation patterns from circular aperture horn antennas, is obtained by assuming an aperture distribution consisting of the fields of cylindrical waveguide modes. A technique is presented for using a linear combination of the radiation pattern functions to approximate a desired radiation pattern. Linear combinations of the radiation pattern functions resulting in maximum secondary gain, when used to illuminate a paraboloidal antenna, are obtained empirically. Using spherical wave theory, maximum performance theoretically obtainable from an antenna is derived as a function of the aperture size of the feed system; the feed efficiency resulting from these theoretical limits on performance is compared to the feed efficiency of patterns obtainable from circular aperture horn antennas, and to experimental results of attempts to realize optimum circular aperture horn patterns.     

Design of a broadband planar cavity-backed circular patch antenna

This paper presents a design of a low-profile cavity-backed circular patch antenna for broadband applications. By using substrate integrated waveguide (SIW) based cavity and feeding mechanism, a planar cavity-backed patch antenna is realized. The proposed study demonstrates that a wide impedance bandwidth can be achieved by employing a rectangular SIW-based cavity underneath the conventional circular patch. Additionally, to generate circular polarization (CP), the patch has been reduced diagonally and shorted by a via-probe. Finally, a CP SIW-based antenna is designed and operating for a wide impedance bandwidth of 23.10% below −10 dB criteria, ranging from 9.09 GHz to 11.40 GHz and axial-ratio (AR) bandwidth of 270 MHz (10.30–10.57 GHz). The proposed design is fabricated by means of a printed circuit board (PCB) procedure. The simulated results are validated with the experimental one which agrees well with each other in the terms of S₁₁, antenna gain, AR and radiation patterns. Moreover, the proposed design exhibits unidirectional radiation characteristics with the measured peak gain of 6.6 dBic while maintaining planar integration.     

Analysis of horn radiators having the complex form cross-section and aperture

An approach to the calculation of radiation patterns and matching characteristics with free space of waveguide-horn radiators having the cross-section and aperture of complex form has been proposed. Solutions were obtained for rectangular and circular ridged radiators with due regard for the proper numbers of equivalent ridged waveguides in the known expressions for the reflection coefficient and radiation patterns of open ends of waveguides having the simple (rectangular and circular) form. The possibility of using the obtained solutions for the practical calculations with the required accuracy at a much smaller computational complexity as compared with similar solutions has been shown.     

Broadening of primary feed patterns by small E-plane slots

It is shown that the radiation patterns of a circular waveguide with a corrugated flange can be broadened by using small E-plane slots. These slots tend to improve the amplitude patterns of the feed, but introduce some phase variations in the axial radiation.     

改进的GPS抗干扰自适应天线阵性能研究

文章提出了一种用于GPS接收机的新型抗干扰自适应天线阵,并给出了对其方向图和输出信干噪比的仿真过程.比较了在相同的信号环境时,该天线阵与常用的均匀直线阵、等间隔圆形阵的性能.结果表明,使用该自适应阵可以改善天线阵的方向图,提高输出信号干扰噪声比SINR,增强接收机的抗干扰能力.     

Circularly polarized circular sector dielectric resonator antenna

A circular sector dielectric resonator antenna (DRA) with circular polarization and a single feed is investigated and demonstrated. The design utilizes the radius to height ratio and feed position of the circular sector DRA to excite two resonant modes that are spatially orthogonal in polarization and in phase quadrature. Experimental results are provided for the design and these demonstrate that the circular sector DRA produces circular polarized radiation with axial ratio less than 3 dB over a 10% bandwidth     

圆形波纹槽波导终端的辐射特性研究

本文根据Floquet定理 ,考虑了圆形波纹槽波导内壁周期性结构而产生的空间谐波的影响 ,研究了这种波导终端的辐射特性。首先 ,利用Kirchhoff Huygens的积分公式 ,得到了这种波导终端辐射器中HE( 1)11模在远区的辐射场 ;然后 ,在一阶空间谐波近似的条件下 ,通过数值计算得到了该波导终端的辐射方向图 ;最后 ,给出了圆形波纹槽波导的各几何参数对其辐射特性的影响 ,得到了一些具有实际指导意义的结论。     

复杂环境对漏泄圆波导辐射特性的影响

漏泄圆波导应用于城市轨道交通时, 其辐射特性容易受到其附近复杂环境的影响, 进而影响到无线通信系统的正常运行.以雪覆盖为例, 研究了不同厚度、不同湿度的雪对漏泄圆波导辐射特性的影响, 提出了抵抗恶劣环境影响的措施.结果表明:积雪对漏泄圆波导的近场场强影响比较明显, 且波导的远场随雪湿度与厚度的增大而降低; 通过在漏泄波导表面加一层介电常数接近空气的泡沫塑料层, 可以有效降低雪对漏泄波导辐射特性的影响, 从而提高无线通信系统的可靠性.       

基于MEI吸收边界条件的导体柱散射问题模拟

首次在圆柱坐标系时域有限差分 (FDTD)法中采用基于时域不变性测试方程 (MEI)方法的吸收边界条件 ,对导体圆柱的电磁散射问题进行了数值模拟研究。在相同计算条件下 ,与应用Bayliss Turkel二阶辐射边界条件的FDTD结果相比较 ,直观地表明MEI方法结果与解析解吻合更好     

Fast Room Temperature Detection of State of Circular Polarization of Terahertz Radiation

We report on a room temperature detector which allows to determine and monitor the state of polarization of terahertz radiation with picosecond temporal resolution. The detector is based on the circular photogalvanic effect recently observed in GaAs/AlGaAs quantum wells. The circular photogalvanic effect yields in response to elliptically polarized radiation a current signal proportional to the degree of circular polarization. The peak current signal occurs in unbiased samples for circular polarization, vanishes at linear polarization and changes sign by switching the helicity from right-handed to left-handed. The detector consists of a (113)A MBE grown pGaAs/AlGaAs multiple quantum well structure. The response has been measured in the wavelength range between 76 μm and 280 μm at normal incidence of the radiation on the sample.     

纵振水声换能器发送电压响应频带展宽补偿

讨论了水声换能器发送电压响应频带展宽的补偿方法。通过对发送电压响应级表达式进行分析,按照带宽内恒定声源级的要求,反推换能器两端激励电压的比值,用该比值对换能器激励电压进行加权补偿,得到了约两个倍频程接近恒定声源级的宽带换能器。文中理论分析和实验结果吻合,是实现超宽带换能器带宽内恒定声源级的一种较有效的方法。     

Multifrequency Waveguide Orthomode Transducer

This paper presents the design and development of a multifrequency probe-coupled orthomode transducer (OMT) using a circular waveguide as the primary waveguide and a rectangular waveguide as the secondary waveguide. Design is presented for a common OMT operating at 6.6, 10.65, 18, and 21 GHz using four cascaded circular waveguide sections with different cross-sectional dimensions. An innovative design technique is used to minimize the inter-port coupling and to maximize the power in the dominant mode to get the required radiation performance at all the frequency bands using a common radiating aperture. The simulated and measured parameters of the OMT and the horn fed by this OMT have been presented.