基于改进遗传算法的阵元失效校正方法

阵列天线中阵元失效,其方向图的副瓣电平会升高、主瓣变宽。保留遗传算法前期迭代的最优个体为新初始种群对遗传算法进行改进,以加快收敛速度和防止最佳染色体缺失。并利用基于优势保留的改进遗传算法,针对-40dB 的26 单元阵列,随机缺失3 单元后进行优化,恢复原方向图副瓣水平。结果表明,该算法能够有效减少阵元缺失后方向图的恶化。     

A novel amplifying antenna array using patch-antenna couplers-design and measurement

This paper proposes a novel amplifying antenna array using the patch-antenna coupler formed by placing one or two open-ended microstrip lines (coupled lines) near and along the nonradiating edge(s) of a patch antenna. An X-band five-element array with broadside 25-dB Chebyshev radiation is demonstrated. When the input signal is fed to the center element, with most of the power radiating from the antenna, part of it is tapped to the coupled lines, amplified by an FET amplifier, and fed to the next antenna element. This process is repeated after all the antenna elements are fed with suitable power. The amplitude distribution of the fields radiated from the antennas is controlled by the coupling coefficient from the patch to the coupled line, which, in turn, is governed by the coupling length and gap between the patch and line. The measured return loss of the designed five-element array is -27 dB at the center frequency of 10 GHz with 2% 10-dB bandwidth. The radiation pattern possesses a transmitting gain of 15.9 dB, a half-power beamwidth of 17/spl deg/, and a sidelobe level of -22 dB.     

Minimization in variations of different parameters in different φ planes of a small-size concentric ring array antenna using firefly algorithm

The radiation pattern of a small-size concentric ring array antenna does not remain φ-symmetric, if the array is made with an appreciably lesser number of antenna elements. The sidelobe level, first null beamwidth (FNBW), half-power beamwidth (HPBW), and the null depths of the radiation pattern change significantly in different φ planes. An efficient pattern synthesis method has been developed in this work to reduce the variation of sidelobe level, FNBW, and HPBW of a small-size concentric ring array of isotropic antennas, for different φ cuts. It is done by finding out an optimum set of amplitude distribution of the array elements using firefly algorithm. The sidelobe level and the first null depth of the array are kept below a desired value for all the defined φ cuts. The directivity of the optimized array and the uniform array has been computed. The variation of all these parameters for different φ cuts has been compared to the same array with uniform excitation among the elements.     

Bi-directionally fed phased-array antenna downsized with variable impedance phase shifter for ISM band

A novel bi-directionally fed phased-array antenna (BiPA) is presented. A BiPA can operate at half the phase shift of the conventional antenna with the same performance, leading to smaller size and lower cost. Main components of a BiPA are antenna elements and variable impedance phase shifters (VIPSs). The VIPS consists of three resonant circuits that include variable capacitors, it is applicable for both functions as a power divider and as an impedance-matching device, since the input/output impedance and the phase shift can be independently varied. The BiPA with a VIPS is simulated and evaluated at a 2.45-GHz industrial-scientific-medical band. The measured results agree well with the simulated ones. The performances of the VIPSs are confirmed as 1.4 dB in insertion loss, and -17dB in return loss for a phase shift of 0/spl sim/80/spl deg/ with the control voltage from 0- to 3.5-V DC, and the measured radiation pattern of the BiPA is /spl plusmn/30/spl deg/ in the steering angle, 24/spl deg/ in beamwidth, and -9dB in the sidelobe. Furthermore, an enhancement of the sidelobe suppression can be expected by changing the power ratio of each antenna element.     

Aperture-Sparsity Analysis of Ultrawideband Two-Dimensional Focused Array

We investigate the effects of aperture sparsity on the focusing performance and the angular-resolution capability of a two-dimensional focused array antenna excited by ultrawideband (UWB) impulse waveforms. The UWB-focusing array is characterized by a planar square aperture and a design parameter referred to as array spatial bandwidth. Spatial bandwidth is a function of the number of array elements, inter-element spacing, and frequency bandwidth. Performance analysis is carried out by generating computer plots of three-dimensional and two-dimensional antenna patterns for different values of array spatial bandwidth that hold for large aperture sparsity and large aperture density. The antenna patterns are peak-amplitude pattern, peak-power pattern, and energy pattern, whose narrow beamwidth and low sidelobe level are robust against aperture sparsity that may be caused by removed or failed elements. The half-power beamwidth (HPBW) of the antenna patterns, the focal distance, and the far-field distance of the UWB-focused array are expressed in terms of array spatial bandwidth. Computer simulation results show that UWB-focused-array beamforming based on impulse waveforms achieves efficient focusing of the radiation energy in the radiation-near-field region and beyond, and yields improvement in focusing performance and angular resolution for increased values of array spatial bandwidth. Such practical advantages are achieved without encountering grating lobes, large sidelobe level, or distortion of the radiation beam pattern that often limit the performance of the conventional narrowband phased array antennas.      

Ka频段单脉冲多层微带阵列天线设计与优化

描述了多层微带阵列天线,辐射单元通过带状线一个地板耦合馈电。为获得好的旁瓣抑制能 力及加工容差,采用遗传算法优化,得到工程上实用的天线口径分布。制作了一个天线,获 得27.3 dB的增益,波束宽度4.2°。实测结果表明在Ka频段实现了100%的旁瓣抑制 。     

一种串馈的非规则天线阵

均匀规则阵列天线的副瓣电平较差,且波束宽度较宽,不太适合于一维高精度相控阵雷达系统.针对这些要求,提出了一种基于串联馈电网络结构的非规则天线阵列.该阵列采用串馈方式,结合带空腔的微波多层板技术,通过带状线缝隙耦合方式,避免了背向辐射,同时获得宽带特性.该阵列采用遗传算法对阵列进行优化,获得低于-18 dB的理论副瓣电平,同时相比均匀规则阵而言,波束宽度仅有0.2°的拓宽.对于20°的波束宽度而言,该波束宽度扩宽量可以忽略不计.该阵列的实测2:1驻波带宽为19.8%,方向图带宽为12.2%,在方向图带宽内,阵列的实测副瓣电平低于-16 dB,阵列的带内测试增益高于11.7 dBi,实测结果和理论设计相吻合,表明该天线阵列适用于一维相控阵天线.     

77 GHz汽车角雷达宽波束平坦增益阵列天线设计

设计了一款基于波束赋形技术的宽波束、平坦增益平面阵列天线,用于汽车角雷达系统.该阵列天线由三个1×10串馈线阵组成,串馈线阵采用单元不等间距分布的Dolph-Chebyshev天线综合法进行设计以降低副瓣.为了满足汽车角雷达宽视场角(field of view,FOV)的需求,对平面阵列天线采用波束赋形技术以展宽方位面...     

An investigation of concentric ring antennas with low sidelobes

An analysis is made of circular antenna arrays with diameters being 2 to9lambda(the minimum inner circle diameter being0.4lambda) containing 3 to 18 concentric circles. For the purpose of computation of the array factor the elements of the array are assumed to be isotropic radiators. The elements of each circle have equal current amplitudes and are phased so that the contributions of all the elements add in phase in the direction of the main beam. The Chebyshev radiation pattern function is approximated by a truncated Fourier-Bessel series, from which the current amplitude of each circle is obtained. From these current amplitudes a method for computing the current amplitude to excite a new distribution of fewer circles is shown. Also, an empirical method is given for improving the sidelobe level of the radiation pattern by adding an element to the center of the array. A number of circles in the array sufficient to avoid pattern deterioration is found to be the integer nearest to5d/4lambdafor -20 and -30 dB sidelobe level and4d/3lambdafor -40 dB, wheredis the diameter of the array. This represents a large reduction in the number of circles needed over the Fourier-Bessel series representation in the case of large antennas. Experimental verification of the computed pattern is made for an array of two concentric circles with diameters of0.8lambdaand1.6at a frequency of 90 Mc/s. The elements of the array were vertical monopoles.     

Design of a minimum-loss series-fed foldable microstrip

The design and analysis of a series-fed, low-loss, inverted microstrip array antenna, operating at 1.413 GHz is presented. The array antenna is composed of two subarrays consisting of an equal number of microstrip patches connected together through a series microstrip line. The subarrays are coaxially fed 180/spl deg/ out of phase. This approach ensures a symmetric radiation pattern. The design approach for obtaining a low sidelobe ratio and a low loss microstrip array is accomplished using the IE3D code. Experimental and simulated data are presented and discussed.     

Design of unequally spaced arrays for performance improvement

Classical antenna array synthesis techniques such as Fourier, Dolph-Chebyshev and Taylor synthesis efficiently obtain array current distributions for equally spaced arrays that generate a desired far-field radiation pattern function or keep important parameters like beamwidth and sidelobe level within prescribed performance bounds. However, the concept of optimization of the field pattern (e.g., by decreasing sidelobes or beamwidth) of an given equally spaced array realization by altering its element spacings still represents a challenging problem having considerable practical advantages. These include reduction in size, weight, and number of elements of the array. This paper describes a new approach to synthesis of unequally spaced arrays utilizing a simple inversion algorithm to obtain the element spacings from prescribed far-zone electric field and current distribution, or current distributions from prescribed far-zone electric field and element spacings     

Dual-polarized slot-coupled patch antennas on Duroid with teflonlenses for 76.5-GHz automotive radar systems

A dual-polarized 76.5-GHz microstrip patch and teflon lens antenna system was designed, constructed, and tested. A receiver (RX) array of three dual-polarized microstrip patches was coupled through a 10-cm-diameter lens to produce radiation patterns with 3° beamwidths and beam crossovers of -3 dB. The transmitter (TX) consisted of a single dual-polarized microstrip patch coupled through a 2.5-cm-diameter lens to produce a 10° beamwidth. Slot-coupled patches were used to isolate the microstrip feed circuit from the radiating elements. The antennas and feeds were fabricated on commercially available 5880 Duriod substrates. Cross-polarization levels were less than -20 dB and were typically less than -30 dB over the entire beam at the design frequency. First sidelobe levels were no greater than -15 dB and were typically closer to -20 dB. Stepped and unstepped versions of the 10-cm-diameter receive lens were designed and fabricated. Antenna system sidelobes levels were lower with the stepped lens while the cross-polarization levels were comparable     

Sidelobe suppression of planar array antennas by the multistage decision method

The sidelobe level of a planar array antenna with equal amplitude excitation can be suppressed by element thinning. The method of element thinning employed here is a kind of multistage decision procedure or steepest descent approach. Although this method gives the local optimum results, the reduced sidelobe level is assured to be within the obtained level over the whole radiation region. The sidelobe level, for example, can be suppressed -29.7 dB where the array contains 3120 elements arranged within a circular aperture capable of 5815 elements if fully filled. The computation time is also discussed, and it is shown that the computation time decreases drastically by the use of the design method.     

Optimum scannable planar arrays with an invariant sidelobe level

This paper presents two alternative methods for determining the current distribution in the elements of a scanning rectangular array which is optimum in the sense that its radiation pattern has a constant sidelobe level and a narrowest beamwidth in all directions. Exact formulas for both even and odd numbers of elements are given. The dependence of the main-lobe beamwidth on the total number of elements, the element spacing, the sidelobe level, and the scan angle is studied in detail. The minimum required number of controlled elements in a square array with electronic beam scanning over a specified sector for a guaranteed upper limit on beamwidth without grating lobes is determined. Numerical results are included, which illustrate many interesting features of the new design technique.     

随机误差对数字波束形成系统性能的影响

文中针对数字波束形成系统,推导出阵列天线的通道幅相误差和阵元位置误差对波束方向图的第一副瓣、零陷深度及半功率波束宽度影响的一般规律。并且对数学公式进行了详细的推导。分析与仿真结果表明：随机误差对波束方向图性能的影响主要与天线阵列的权系数和阵元数目有关。     

双圈圆阵方向特性分析

研究了双圈圆阵在两种不同放置情况下的方向特性, 主要包括阵列方向图的指向、主瓣波束宽度和副瓣峰值电平等.首先, 建立了双圈圆阵的阵列模型, 推导方向图公式并推广到多圈圆阵的情况, 随后对其进行了理论分析.其次, 通过大量仿真实验, 分析了主瓣的半功率点波束宽度和副瓣峰值电平以及扫描角分别与内、外圈阵元数以及内、外圈阵元半径之间的关系.最后, 对理论分析和仿真结果进行综合梳理, 发现在阵元内、外半径之比为0.5左右时副瓣电平最低, 波束宽度会随着内圈阵元数增大而增大, 随外圈阵元数增大而减小等结论.实验结果可为实际工程应用中合理设置阵元数目以及阵元位置提供理论参考.     

基片集成波导缝隙稀疏阵天线的设计

设计了一种应用于雷达系统中的低成本低副瓣阵列天线, 该天线阵包含256个辐射单元, 由四个64单元的子阵组成, 采用波导合成网络进行功率合成.天线单元采用空气同轴馈电的角锥喇叭, 空气同轴馈线内外导体呈方型结构, 其终端为短路馈电方式, 实现了内导体的自支撑设计和较低的传输损耗, 并依据综合幅度分布采用若干数量的不等功分器进行低副瓣设计.测试结果表明, 小于2的驻波带宽为0.5 GHz, 相对带宽为7.5%.另外, 中心频率的增益为30 dB, 增益大于29.5 dB的带宽为0.2 GHz, E面和H面的旁瓣电平为28.5 dB和29 dB.     

Carrier-to-noise ratio and sidelobe level in a two-laser modeloptically controlled array antenna using Fourier optics

The carrier-to-noise ratio of the microwave signal and the reduction of the antenna sidelobe are discussed for an optically controlled array antenna whose microwave aperture distribution is generated and controlled using Fourier transform and optical/electrical conversion. A two-laser model using two laser diodes whose frequency difference is set to the desired microwave frequency is proposed and compared with a single-laser model using an external modulator. The two-laser model seems to be favorable from the viewpoint of available laser diode output power. The required laser output for the two-laser model can be about 10 dB less than that for the single-laser model. Moreover, relationships between the antenna radiation characteristics and the aperture size of an image mask are investigated. It is clarified that the sidelobe level can be reduced about 20 dB without changing the gain and beamwidth by using a reference optical beam with a tapered amplitude distribution     

Tapered beamforming for concentric ring arrays

In this paper, some conventional filtering windows are modified and applied to uniform concentric circular antenna arrays (UCCA) for spatial smoothing and sidelobe reduction. The modified windows are applied to individual rings of the array that will taper the corresponding current amplitudes. The resulted sidelobe level, beamwidth and stability for amplitude errors are discussed for the different proposed tapering windows where it shows a sidelobe reduction to about 49 dB as in the case of Binomial UCCA while the Hamming window shows the most immunity to tapered amplitude errors.     

一种空气同轴馈电的X波段低副瓣阵列天线

设计了一种应用于雷达系统中的低成本低副瓣阵列天线, 该天线阵包含256个辐射单元, 由四个64单元的子阵组成, 采用波导合成网络进行功率合成.天线单元采用空气同轴馈电的角锥喇叭, 空气同轴馈线内外导体呈方型结构, 其终端为短路馈电方式, 实现了内导体的自支撑设计和较低的传输损耗, 并依据综合幅度分布采用若干数量的不等功分器进行低副瓣设计.测试结果表明, 小于2的驻波带宽为0.5 GHz, 相对带宽为7.5%.另外, 中心频率的增益为30 dB, 增益大于29.5 dB的带宽为0.2 GHz, E面和H面的旁瓣电平为28.5 dB和29 dB.