Electromagnetic modes in conical transmission lines withapplication to the linearly tapered slot antenna

A transmission line analysis of the bow-tie antenna and the linearly tapered slot antenna (LTSA) is presented. These structures belong to the class of conical transmission lines defined here in terms of conical coordinates. A complete set of solutions of the Helmholtz equation is obtained exhibiting TE and TM modes. Modal fields are expressed by Lame (1837) and Bessel-Schelkunoff functions. TE and TM eigenmode analysis is particularized to the bow-tie structure. Bow-tie antenna and LTSA are shown to be dual conical transmission lines by the image method and Babinet's principle. The modes of LTSA are calculated on the basis of the results obtained for the bow-tie structure. The radiation pattern of the LTSA is computed as the integral of a closed-form expression of the dyadic Green's function weighted by the modal electric field distribution over the slot aperture. The obtained dominant mode radiation patterns are validated by measurements from the literature. The radiation patterns of the first two-order modes are calculated and compared     

Radiation and scattering analysis of infinite arrays of endfireslot antennas with a ground plane

A Green's function moment-method analysis of infinite arrays of endfire slot antennas is described that includes the constant width slot antenna (CWSA) and the linearly tapered slot antenna (LTSA), with a ground plane. The method utilizes an application of equivalence at a plane in front of the array which facilitates the extension of this analysis to antennas printed on protruding dielectric sheets and/or the addition of a radome. Numerical calculations are compared with waveguide simulator experiments for CWSA and LTSA arrays as well as several less complex problem. Relevant numerical considerations and convergence issues are also discussed     

Fan-Beam Millimeter-Wave Antenna Design Based on the Cylindrical Luneberg Lens

A new design of two-dimensional cylindrical Luneberg lens is introduced based on TE₁₀ mode propagation between parallel plates, with special focus on ease of manufacturing. The parallel plates are partially filled with low cost polymer material (Rexolite epsiv_r = 2.54) to match Luneberg's law. A planar linear tapered slot antenna (LTSA) is inserted into the air region between the parallel plates at the edge of the Luneberg lens as a feed antenna, with fine positioning to the focal point of the Luneberg lens to optimize the antenna system performance. A combined ray-optics/diffraction method is used to obtain the radiation pattern of the system and results are compared with predictions of a time domain numerical solver. Measurements done on a 10-cm Luneberg lens designed for operation at 30 GHz agree very well with predictions. For this prototype, 3-dB E- and if-plane beamwidths of 6.6deg and 54deg respectively were obtained, and the sidelobe level in the E-plane was -17.7-dB. Although the parallel plate configuration should lead to a narrow band design due to the dispersion characteristics of the TE₁₀ mode, the measurement results demonstrate broadband characteristics with radiation efficiencies varying between 43% and 72% over the tested frequency band of 26.5-37 GHz. The designed cylindrical Luneberg lens can be used to launch multiple beams by implementing an arc array of planar LTSA elements at the periphery of the lens, and can be easily extended to higher mm-wave frequencies.     

New techniques for exciting linearly tapered slot antennas with coplanar waveguide

Two new techniques for exciting a linearly tapered slot antenna (LTSA) with coplanar waveguide (CPW) are introduced. In the first approach, an air bridge is used to couple power from a CPW to an LTSA. In the second approach, power is electromagnetically coupled from a finite CPW (FCPW) to an LTSA. Measured results at 18 GHz show excellent return loss and radiation patterns.<>     

Evaluation of the BICGSTAB(l) algorithm for thefinite-element/boundary-integral method

We discuss the application of non-stationary Krylov-subspace-based iterative solvers to linear systems resulting from the application of the finite-element/boundary-integral method. A fairly new conjugate-gradient-based solver, BICGSTAB(l) is further described. The performance of several solvers is tested on a linearly tapered slot antenna (LTSA). Results showing the convergence characteristics and memory requirements are also given     

Millimeter-wave tapered-slot antennas on synthesized lowpermittivity substrates

This paper presents 30-GHz linear-tapered slot antennas (LTSA) and 94-GHz constant-width slot antennas (CSWA) on synthesized low dielectric constant substrates (ϵ_r=2.2). The performance of tapered-slot antennas (TSA) is sensitive to the effective thickness of the substrate. We have reduced the effective thickness by selectively machining holes in the dielectric substrate. The machined substrate antenna radiation patterns were significantly improved independent of the machined hole size or lattice as long as the quasi-static effective thickness remained the same, even if the hole/lattice geometry is comparable to a wavelength. The method was applied at 94 GHz on a CSWA with excellent radiation pattern improvement, making it suitable for f/1.6 imaging array applications     

Walled LTSA Array for Rapid, High Spatial Resolution, and Phase-Sensitive Imaging to Visualize Plastic Landmines

We propose a walled linearly tapered slot antenna (LTSA) array to visualize plastic landmines. Previously, we reported an adaptive nonlinear visualization system based on a complex-valued self-organizing map (CSOM) that deals with complex amplitude texture in reflection images at multiple frequencies. The system distinguishes landmines from clutter by paying attention to textural features obtained by high spatial resolution and wideband reflection measurement. Because the system employed a mechanical scan of a pair of horn antennas, the measurement required a long time. An array antenna can reduce the time. The antenna element to be used there should therefore be compact and wideband. This paper reports the design and fabrication of a walled LTSA array visualization system. The antenna element has a 14 times 28 mm aperture size, and works at the 8-12 GHz frequency band. Because the structure is a simple combination of glass epoxy substrates and metal plates, we can easily fabricate low-cost and lightweight arrays. Electrical switches realize a high-speed scanning of 12 times 12 = 144 elements in total. We also report the results of a visualization experiment, in which plastic landmines are clearly visualized with the array in combination with the adaptive CSOM processing. Detection of landmines at frequencies of 10 GHz is only likely to be possible for targets buried a few centimeter deep or where the soil attenuation is very low. This might be a severe limitation of applicability of the method, as in field conditions soil attenuations of 10 dB or considerably more are commonly encountered, requiring the radar to operate at frequencies below 2-3 GHz. The best solution may be a multisensor system comprising these complementary high- and low-frequency radars.     

Integrated uniplanar transition for linearly tapered slot antenna

This paper presents the design, fabrication, and numerical modeling of two new uniplanar microstrip-to-coplanar strip (CPS) line transitions and a new variant of the linearly tapered slot antenna (LTSA). This new variant with an integrated uniplanar microstrip-to-coplanar strip line feed is called a V-LTSA. The advantages of these transitions in packaging and monolithic microwave integrated circuits (MMIC) integration are listed. The two transitions and the feed are modeled using finite difference time domain (FDTD) method. The overall agreement between the measured and modeled return-loss and insertion-loss characteristics of two back-to-back transitions is good. The resonance frequencies predicted by the FDTD method are within a few percentage points of the measurements. Furthermore, the V-LTSA with the feed is experimentally shown to have a wide return loss (⩽-10 dB) bandwidth, good radiation patterns, and low cross-polarization. The gain of the V-LTSA is 9 dB at the design frequency of 10 GHz. A proof-of-concept package to house the feed is experimentally evaluated and shown to have negligible effect on the antenna characteristics. This type of antenna readily integrates with MMIC packages in an array having a brick architecture. The V-LTSA has potential applications in phased arrays     

Antenna Effective Aperture Measurement With Backscattering Modulation

A scattering measurement method for antenna characterization is described. The antenna backscattering is modulated by an oscillator circuit. The modulation begins, when a known RF power is transferred to the oscillator circuit from the antenna. This enables the measurement of the effective aperture of the antenna, from which the antenna bandwidth and radiation pattern are obtained. A theory for antenna aperture measurement is developed using a simple circuit model for the antenna-oscillator system. A dipole and a PIFA with a reactive input impedance at the application frequency were measured. The antenna aperture was measured to an accuracy of 9%, and the measurements complied with simulated and measured references. The method provides simple and accurate bandwidth and radiation pattern measurements with the reactive load the antenna is designed to work with.     

基于改进局部切空间排列的流形学习算法

局部切空间排列是一种广受关注的流形学习算法,其具备实现简单、全局最优等特点,但其难以有效处理稀疏采样或非均匀分布的高维观测数据。针对这一问题,该文提出一种改进的局部切空间排列算法。首先,提出一种基于L1范数的局部切空间估计方法,由于同时考虑了距离和结构因素,该方法得到的切空间较主成分分析方法更为准确。其次,在坐标排列步骤为了减小排列误差,设计了一种基于流形结构的加权坐标排列方案,并给出了具体的求解方法。基于人造数据和真实数据的实验表明,该算法能够有效地处理稀疏和非均匀分布的流形数据。     

舰载雷达天线方向图拟合方法的研究

本文在把阵元间幅相不一致性归结为阵元方向图畸变基础上,提出利用海杂波作为定标源对方向图进行拟合的几种方法.文中详细叙述了利用最小二乘法及总体最小二乘法对方向图进行拟合的具体方法.模拟结果表明总体最小二乘法是几种方法中的最优方法.     

一种基于大动态微波功率测量的雷达天线方向图测试方法

本文提供了一种雷达天线方向图新的测试方法,利用大动态范围的微波小功率计,最低可测量出微瓦级的功率信号,直接测量雷达天线各个方位接收到的功率信号,解决了传统的雷达天线方向图测试方法步骤繁多、测量误差大、动态范围小等不足,适用于具有良好电子对抗要求的新型低副瓣或极低副瓣雷达天线的方向图测试,完全满足工程测试的需要。     

有源多波束天线方向图测试方法研究

论述了利用高精度三轴天线测试转台,测试有源多波束天线立体方向图的方法。简述了天线立体方向图的测量程序。给出了用二维坐标表示多波束立体方向图的方法,并简述了利用MATLAB软件对测试数据进行处理获得多波束天线立体方向图的方法,对方向图测试误差进行了分析。最后,给出了某工程有源多波束天线方向图的测试结果。实践证明:该方法是切实可行的。     

A Miniature Quadrifilar Helix Antenna for Global Positioning Satellite Reception

The design is described of a very compact quadrifilar helix antenna. A hollow ceramic rod is used as a dielectric load to reduce antenna size, which is only 2.7% of an air-loaded quadrifilar helix antenna. A simple equivalent circuit is established for the proposed quadrifilar helix antenna to demonstrate impedance characteristics. A self-phasing method for achieving circular polarization is also proposed. This method is convenient for tuning circular polarization. Additionally, a compact matching structure is designed to match the proposed antenna, which only utilizes short transmission-line sections and one capacitor. For experiments, the proposed antenna is designed at 1.575 GHz such that it can be utilized for global position system. Measurement and simulation results agree. A hemispherical pattern with a beamwidth of 150 $^{circ}$ is measured. This circular-polarized pattern with a wide beamwidth is feasible for mobile applications.      

Probe compensated near-field measurements on a cylinder

A new method is developed for determining the farfield pattern of an antenna from probe compensated near-field measurements over the surface of a right circular cylinder enclosing the antenna. The method is derived by first expanding both the field radiated by the antenna and the field radiated by the measurement probe, when it is used as a transmitter, into cylindrical wave expansions. The Lorentz reciprocity theorem is then used to solve for the field radiated by the antenna from the probe output voltage. It is shown rigorously that the antenna pattern can be determined independently of the characteristics of the measurement probe provided that certain calibration data are known. A method for determining these data from the measured far field radiated by the probe is described. It is shown that the necessary numerical integration can be performed with the fast Fourier transform algorithm. Experimental results are presented to validate the theory and to demonstrate its practicality from a measurement and computational viewpoint.     

一种计算赋形天线增益下降的简单方法

基站天线常采用赋形技术,以提高通信质量和减小对邻区的干扰,但采用赋形技术会导致天线的增益下降,通过方向图积分方法来计算和评估赋形天线的增益下降,计算过程复杂。介绍了一种通过分析基站天线接收信号过程中馈电网络功率合成的方法,只需几步简单的运算即可得出赋形基站天线的增益下降情况。     

一种小型平面超宽带天线的设计与研究

提出了一种新颖的小型平面超宽带(UWB)天线.该天线由微带槽天线的基本结构变形而来,为获得超宽带频率特性,设计时馈电微带线采用了渐变结构的叉形调谐支节,金属底板的开槽设计成对称多边形.首先通过数值计算来获得最佳的天线几何尺寸,并制作了实际的样品.对天线的反射特性、方向图以及增益都进行了测试,然后利用时域有限差分(FDTD)方法计算了天线收发脉冲信号的保真度.研究结果显示该天线具有良好的超宽带特性.     

Filtering environmental reflections in far-field antenna measurement in semi-anechoic chambers by an adaptive pattern strategy

A method to perform antenna far-field measurements in semi-anechoic chamber is presented. The method requires the measurement of the amplitude and phase of the pattern of the antenna under test in different spatial positions. The data are elaborated to estimate the direction of arrival of the reflected signals and to synthesize a receiving pattern with s in these directions. Experimental results confirm the effectiveness of the technique.     

相控阵雷达系统建模中的天线仿真技术

在对相控阵雷达系统建模仿真工作中,相控阵天线建模仿真是其中的关键所在。首先研究和探讨了平面相控阵天线仿真数学模型,给出了方向图数学函数。接着介绍了相控阵雷达系统建模中天线建模仿真的两种主要方法,多通道阵元级合成方法和方向图数据载入法。阵元合成法基于方向图数学函数给出了常规和差多通道的仿真算法,方向图载入法研究了如何对数据文件进行双线性插值来计算任意角度的增益。最后利用多通道阵元级合成方法进行了天线方向图建模仿真,通过仿真结果表明该算法的正确性,并说明两者仿真方法的适用条件。     

Features of formation of the patterns of a monopulse active phased array antenna with a dome lens

A method for the control of the transmission coefficients of antenna elements of a system comprising an active phased array antenna (APAA) and a dome lens, which ensures formation of a deep boresight null of the elevation difference pattern, is proposed. The effect of the control method on the characteristics of receiving monopulse channels of the APAA depending on the intrinsic noise of antenna elements is analyzed. The results of the well-known theory of reception of a nonplane wave by an antenna with continuous aperture are extended to the case of an array antenna.