Wideband microstrip array antenna with sidelobe cancellationchannels

An antenna array for wideband operation (up to 70%) is presented. The structure has low windloading area and consists of parallel printed circuit boards (PCB) with microstrip dipoles, feed network and metal fences placed between the PCBs. The low profile, low weight antenna array forms the main beam and three difference patterns for sidelobe cancellation. Experimental results are compared with calculations for both microstrip dipole and array     

L波段双脊裂缝波导低副瓣阵列天线的设计

设计了一种L波段双脊波导裂缝阵列天线。该天线具有好的频率响应特性,实现了低副瓣,水平垂直两个面的交叉极化得到了有效抑制。由于馈电双脊波导的截面尺寸大幅度减小,使得这项研究将有很好的应用前景。     

约束优化实现超低副瓣相控阵的多阶振幅量化

利用约束非线性最优化方法研究超低副瓣相控阵激励振幅的量化综合问题,通过对相控阵天线优化模型加入适当的约束条件,实现了二维可分离超低副瓣相控阵天线多阶振幅量化和单元间互耦的直接修正,该方法适用于各种形式相控阵天线的量化综合,最后给出了一些计算结果。     

Wideband ultralow reverberation antenna for biological sensing

A wideband bow-tie antenna has been designed using the finite-difference time-domain (FDTD) method. When positioned at the surface of a biological tissue half-space, the calculated reflections from the antenna ends are 106 dB below the exciting pulse. This facilitates detection of local weakly-scattering tissue structures     

Near-field antenna measurements using nonideal measurementlocations

We introduce a near-field to far-field transformation algorithm that relaxes the usual restriction that data points be located on a plane rectangular grid. Computational complexity is O(Nlog N) where N is the number of data points. This algorithm allows efficient processing of near-field data with known probe position errors. Also, the algorithm is applicable to other measurement approaches such as plane-polar scanning, where data are collected intentionally on a nonrectangular grid     

有源相控阵天线的近场校准

为实现对相控阵天线的校准,降低幅相误差和阵元失效对天线性能的影响,提出了一种考虑互耦效应的近场校准方法。在利用近场扫描法完成逐一通道校准的基础上,使用旋转矢量法进行二次校准。在应用旋转矢量法（ REV)时,为使被测信号的变化明显,将大规模相控阵天线分为中间、边缘区域进行分区校准。通过二次校准可判定阵元是否失效,提高相控阵天线的幅相一致性;通过分区校准减小阵元间互耦的影响,缩短校准时间。仿真结果表明：此方法用于大型相控阵的校准具有较高的准确性,可改善校准结果。     

Near-field quasi-null control with far-field sidelobe levelmaintenance in line source distributions

An improving method, based on the Taylor line source, that allocates a quasi-null in a specified angular position of near-field pattern, and simultaneously controls the general topography of the far-field sidelobe level without significant loss of directivity, compared with optimal efficiency Taylor distribution, of the latter, is presented. The method is based on the application of the simulated annealing technique, by achieving the complex roots of the pattern distribution. An example is developed that demonstrates this accomplishment     

多输入多输出雷达发射天线低旁瓣设计

多输入多输出(MIMO)雷达发射波形的多样性,为发射方向图设计提供了更多的自由度。针对阵元等功率条件下获得低旁瓣高增益发射波束的问题,提出了一种采用极小极大准则优化设计发射波形相关矩阵的方法,并将该约束优化问题转换为无约束优化问题,便于采用经典迭代法求解。仿真结果表明:采用极小极大准则设计的发射方向图旁瓣区域平坦,最高旁瓣电平接近理论最低值。最后采用循环(CA)算法,获得易于数字阵列系统实现的相位编码信号,使用该相位编码信号得到的实际发射方向图与理论结果匹配良好。     

The design of antenna arrays with tapered sidelobe heights

Arrays for many radar and sonar applications have customarily been designed for equal sidelobe levels. This is, perhaps, as much due to the convenience of the analytical Dolph-Chebyshev technique as to any specific requirement. Using a simple adaptation of a previously reported numerical technique for symmetrical arrays, designs can be obtained whose directional response has a specified taper on the envelope containing the sidelobes. The method is applicable to both sum and difference patterns for both line and planar arrays. However, there seems to be little to be gained by this procedure except in the case when the outer sideiobes are to be more severely controlled.     

Contribution of reflector profile errors to antenna sidelobe radiation

The validity of a simple formula for the level of sidelobe radiation due to profile errors in an antenna reflector has been verified by numerical evaluation of Ruze's integral. The statistical distribution of the sidelobes is discussed before the formula is applied to the practical case of large earth-station antennas. Profile errors may significantly impair the sidelobe performance of these antennas unless adequate tolerances are specified.     

The effect of discrete scatterers on a low sidelobe antenna

The effect of randomly distributed scatterers placed in the far field of an antenna is explored. A technique for predicting the effects of specular scatterers on antenna performance has been developed. Laboratory testing of a low sidelobe antenna indicated an acceptable low sidelobe level. However, when the antenna was field tested, it exhibited average radiated power levels off the main beam that were significantly greater than those anticipated. In an effort to determine the cause of this increase, a computer model of an antenna in a field site has been developed, which includes the calculation of the total scattered power of the antenna main beam and sidelobes from specular reflectors distributed over the far field of the antenna.     

Cross-polarization and sidelobe suppression in dual linearpolarization antenna arrays

In recent years, there has been an increasing interest in dual linear polarization antennas for various purposes, e.g. polarimetric synthetic aperture radar (SAR) imaging. A key design goal for dual polarization antennas is to obtain a high cross-polarization suppression. When using standard techniques for improving the cross-polarization suppression in dual linear polarization antenna arrays undesired sidelobes appear. This paper describes the properties of some known cross-polarization suppression methods and presents a new method for obtaining high cross-polarization suppression and simultaneously avoiding undesired sidelobes     

数字阵列天气雷达低副瓣天线设计

为天气雷达设计一维相扫相控阵天线,方位面副瓣低于-30 d B,波束宽度小于1°,俯仰面接收副瓣低于-40 d B。方位面波束采用窄边波导裂缝阵列天线实现,采用全数字T/R组件精确控制幅度和相位,实现低于-40 d B的俯仰面接收副瓣。测试结果表明,副瓣电平与波束宽度指标与理论值吻合较好,满足指标要求。     

Low sidelobe electronically scanned antenna using identicaltransmit/receive modules

A microwave network is described for use with identical transmit/receive modules such that amplitude-tapered aperture distributions are obtained with no loss. High-efficiency low-sidelobe patterns are calculated for the line source case with sidelobes as low as -27.5 dB. An optimum minimum-loss design is described for arbitrarily low sidelobes. The effects of errors on sidelobes are shown to be the same as in any array. The extension of the technique to the planar array case is presented     

Reduced sidelobe four-beam antenna array fed by modified Butler matrix

A novel four-beam antenna array fed by a modified 4/spl times/8 Butler matrix is proposed. Four 180/spl deg/ directional couplers in conjunction with a 4/spl times/4 Butler matrix are applied to provide a tapered excitation of a linear eight-element switched-beam antenna array. Sidelobes as low as -20 dB for all four beams have been both theoretically and experimentally achieved. A proposed technique of antenna element rotation simplifies the design of a feeding network.     

Near-field probe used as a diagnostic tool to locate defectiveelements in an array antenna

Results of an experimental study are presented in which the near-field probe was used as a diagnostic tool to locate the defective elements in a planar array. The near-field data were processed not only to obtain the far-field patterns of the array under the test, but also to reconstruct the aperture field for diagnostic purposes. The backward transform enables the near-field probe to identify accurately aperture faults at a distance, free of interactions and couplings with the array elements. In practice, to recover the aperture field properly from the near-field distribution, the evanescent components in the computed far-field spectrum must be excluded from the inverse process with fast-Fourier-transform (FFT) techniques. For low-gain array antennas, a correction on the far-field spectrum is required to remove the contribution of the probe and the element factor before the inverse transform, strongly enhancing the resolution     

Whitening of sidelobe powers by pattern switching in radar array antenna

Presented here is a concept for nearly eliminating bias errors in reflectivity and velocity estimates due to power received through antenna sidelobes of pulse Doppler radars. The antenna pattern is switched from pulse to paise among specially designed patterns, with near identical main lobes, but with sidelobes having randomly distributed phases and amplitudes. The sidelobe signal then becomes incoherent without affecting the coherency of the main lobe signal. The whitened sidelobe signal does not bias the mean velocity estimate computed by Doppler processing, and an unbiased estimate of reflectivity can be computed with the knowledge of the mean whitened power level. Pattern design criteria and a method for the design of optimum patterns are developed for a linear array. The extent of sidelobe reduction by way of whitening has been studied in detail for special case of only two patterns switched randomly using a pseudonoise sequence. Pattern switching realizes an effectively low sidelobe pattern without sacrifice of main lobe resolution. A possible extension to two-dimensional arrays is suggested.     

一种双扼流槽双极化低旁瓣阵列天线

设计了一种新型低副瓣双极化阵列天线,阵列单元采用角锥喇叭,利用探针分层正交馈电实现双极化辐射,利用双扼流槽解决了宽波束降旁瓣的难题.在阵列馈电设计中,利用空气同轴线网络实现泰勒加权降旁瓣设计,同时,利用反相馈电技术改善了极化隔离度和交叉极化.实测结果表明：在工作频带9.5 GHz±500 MHz,回波损耗小于-10 dB,俯仰面、方位面方向图旁瓣电平小于-16 dB,极化端口隔离度小于-30 dB,交叉极化电平小于-35 dB.     

Switched-beam antenna based on modified Butler matrix with low sidelobe level

A switched-beam antenna with a low sidelobe level based on a modified n/spl times/n Butler feeding network is proposed. This novel design only requires addition of 180/spl deg/ power dividers in the Butler matrix part. A four-beam prototype is constructed. Measurement indicates that the sidelobe level is significantly reduced.     

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.