共查询到18条相似文献,搜索用时 190 毫秒
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介绍了一种新颖的折叠光路近场准光照射天线设计方法,并成功应用在微波黑体定标源微弱散射的双站测量中. 在双站测量中,传统的小口径天线适用于低频范围,被测目标足够小才能保证远场条件. 与传统基于远场条件出发的小口径天线设计不同,本文所提出的准光照射天线的设计目的是在目标区降低链路衰减,实现相位平坦、幅值边缘衰减的聚焦照射,并可在近场区域内测得目标的远场散射特征. 设计基于准光学设计方法:由主反射镜和平板反射镜共同构成紧凑的折叠光路,首先确定馈源喇叭天线的等效高斯波束参数,然后基于高斯波束传播理论设计主反射镜,再通过全波仿真验证其折叠路径. 仿真分析表明即使馈源采用基本的圆锥喇叭馈源,也可实现良好的聚焦效果. 双站实测数据表明该天线设计达到了设计目的,为亚毫米波近场双站散射测量的开展提供了关键性的波束控制,具备广泛的应用价值. 相似文献
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荣武平 《中国电子科学研究院学报》2010,5(4):430-434
简要介绍了反射面天线近场聚焦测量方法,推导出了有限测试距离时用副反射面纵向偏焦补偿近场相差的计算公式,分析了近场聚焦测量与远场测量的数据结果,并给出了仿真和试验实例,仿真与试验结果吻合较好,近场聚焦法是一种可用于大口径天线性能测量的有效方法。 相似文献
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本文通过矩量法及其高效数值方法(MLFMA)对近距离目标--单脉冲收发天线的电磁互作用进行一体化数值仿真,定量研究了单脉冲天线的近场角度测量特性.在该近场模型中,目标散射近场的幅、相分布和同轴探针激励的喇叭单脉冲天线的辐射场(对应远场和波束)、接收端响应(对应远场差波束)均采用全波数值模拟获得.首先,计算单脉冲天线的辐射场并将其作为对目标照射的激励条件;接着,计算目标散射近场的空间分布;并计算出单脉冲天线所接收到的目标散射场;最后,使用幅值法和相位法计算出单脉冲天线近场测角角度,并在此基础上对近距离测角误差进行研究.在导弹目标算例中,将天线--目标一体化建模和天线口径面上散射近场的幅、相分布计算结果用于近距离条件下单脉冲天线测角误差的研究,并通过频率、距离的变化对测角精度做了对比分析;发现目标近场散射幅、相分布的非均匀性,是导致单脉冲天线近距离角度测量产生较显著的测角误差的主要原因;而频率较低时,测角误差较小.文中给出了物理解释,并提出近距离测向时借助于较低频信号的校正以降低测角误差的建议. 相似文献
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针对Ka波段被动毫米波成像应用,设计了一种由介质透镜与缝隙天线馈源组成的天线系统.将高斯波束理论与光学透镜中的等光程原理相结合,设计了一种大口径介质透镜,该透镜具有良好的聚焦性能;提出了一种新型的共轭直线渐变缝隙天线作为透镜的馈源,该天线呈现出截面小、增益高的优良性能,可以在焦平面上形成密集的馈源阵列.将所设计的介质透镜与馈源天线进行联合仿真,研究结果表明,该系统在距透镜2.81 m处聚焦焦斑为50 mm,并且在±5°偏焦时聚焦焦斑都小于60 mm.所设计的天线系统具备很好的聚焦性能且具有较大的偏焦工作角度,可以适用于被动毫米波近场成像应用. 相似文献
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以安全检查为背景,研究了近距离被动毫米波焦面阵成像的关键技术.其中包括采用基模高斯波束法结合几何光学法分析系统准光路;设计多波束宽角扫描透镜天线;提出一种新型结构的介质棒天线,该天线易于排成紧密阵列且能够为透镜提供良好的照射;研制工作于Ka频段的高灵敏度、小型化直接检波式辐射计等.给出了20通道被动毫米波焦面阵成像系统... 相似文献
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The latest generation of Cassegrain radio astronomy antennas is designed for multiple frequency bands with receivers for individual bands offset from the antenna axis. The offset feed arrangement typically has two focusing elements in the form of ellipsoidal mirrors in the optical path between the feed horn and the antenna focus. This arrangement aligns the beam from the offset feed horn to illuminate the subreflector. The additional focusing elements increase the number of design variables, namely the distances between the horn aperture and the first mirror and that between the two mirrors, and their focal lengths. There are a huge number of possible combinations of these four variables in which the optics system can take on. The design aim is to seek the combination that will give the optimum antenna efficiency, not only at the centre frequency of the particular band but also across its bandwidth. To pick the optimum combination of the variables, it requires working through, by computational mean, a continuum range of variable values at different frequencies which will fit the optics system within the allocated physical space. Physical optics (PO) is a common technique used in optics design. However, due to the repeated iteration of the huge number of computation involved, the use of PO is not feasible. We present a procedure based on using multimode Gaussian optics to pick the optimum design and using PO for final verification of the system performance. The best antenna efficiency is achieved when the beam illuminating the subreflector is truncated with the optimum edge taper. The optimization procedure uses the beam’s edge taper at the subreflector as the iteration target. The band 6 receiver optics design for the Atacama Large Millimetre Array (ALMA) antenna is used to illustrate the optimization procedure. 相似文献
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A fully polarimetric bistatic-radar facility has been constructed at the University of Michigan, to serve as a research tool for improved understanding of the nature of bistatic scattering for point and distributed targets. The facility is capable of operation at 10, 35, and 94 GHz, but only the 10-GHz system is described in the presentation. To meet both the size and design constraints both a horn antenna operating in the far-field, and a parabolic-dish antenna operating in a near-field focused mode, are utilized. A newly developed bistatic-calibration technique, using a flat metal plate, is used to calibrate the facility. Validation results, using a hemisphere over a conducting metal plate, show that the facility is capable of characterizing the radar cross section of a point target to within ±1 dB in magnitude and ±5° in polarization phase difference over a wide range of bistatic angles. Sample data for a point target and a distributed target are presented 相似文献
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Recent experimental results on determination of antenna pattern and power gain from near-field measurements are described. Two new antenna measurement theorems were applied. Measurements were made on an electrically large horn lens, a standard-gain horn and a nominal duplicate of the measuring antenna. Some comparisons with direct far-field measurement results were made. 相似文献
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A new method is presented for calculating near-field antenna gain correction factors directly from measured far-field pattern data by using a spherical wave expansion of the pattern. This eliminates the need for any assumptions regarding antenna aperture field distributions. The only significant assumption in the new method is to neglect multiple scattering between the antennas. The method is applied to the case of a horn antenna. Calculated results are compared to direct measured results, demonstrating agreement to within 0.03 dB. The method is also compared to the method of Chu and Semplak, with similar agreement. The sensitivity of the results to truncation error and noise in the data is also investigated and contrasted to sensitivity of prior methods to errors in the assumed field distribution. 相似文献
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基于夫琅禾费衍射理论,通过对衍射积分的核函数进行近似,推导并得出了简洁的经圆环形孔径衍射的高斯光束远场发散角的近似解析式。在不同衍射孔径外径和不同遮拦比的条件下,将该解析式与严格的夫琅禾费衍射积分进行比较,发现二者求出的远场发散角接近一致,最大误差不超过2.7%。与传统数值积分求取光束发散角相比,该近似解析式在避免繁琐的积分运算同时保持了较高的精度。该解析式成立条件为高斯光束的束腰直径大于等于3.5倍中心遮拦直径,且小于等于孔径直径;在实际工程应用中,特别是具有大口径、小遮拦比特点的空间激光通信光学天线这一应用场景,该条件一般能够被满足。 相似文献
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提出并设计了一种宽带广角覆盖的波束扫描折叠式反射阵列(folded reflect array,FRA)天线. 为了在宽带范围内以及较宽的波束覆盖范围(beam coverage range,BCR)内获得较低的扫描损耗,提出一种考虑照射权重因子、截获功率权重因子以及频率权重因子的多波束优化方法;为了降低FRA天线的剖面,采用小尺寸贴片天线作为馈源,将其与单层反射板集成在一起. 设计了一个尺寸为264 mm×264 mm、工作在Ku波段的11波束扫描的FRA天线,仿真验证本文所提设计方法的有效性,结果表明:该设计在13.5~16.5 GHz的宽带范围内,实现了3 dB波束可覆盖−28°~28°范围,中心频率处最大增益为26.6 dBi,口径效率范围为14%~20.9%,所设计的共口径FRA天线可以获得相当平坦的增益,扫描损耗都在3 dB以内. 该天线具有覆盖范围广、覆盖带宽宽、集成度高、增益高、口径效率高等优点,在无线通信、雷达成像和目标识别等领域具有广阔的应用前景. 相似文献
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Airborne or spaceborne radar systems often require tests before deployment to verify how well the system detects targets and suppresses clutter and jammer signals. The radar antenna diameter can be large and thus the conventional far-field test distance is impractical to implement. The theory and simulations of phase-focused near-field testing for adaptive phased array antennas is discussed. With near-field source deployment, standard phased-array near-field phase focusing provides far-field adaptive nulling equivalent performance at a range distance of one aperture diameter from the adaptive antenna under test. Both main beam clutter sources and sidelobe jammer sources are addressed. The phased array antenna elements analyzed are one-half wavelength dipoles over the ground plane. Bandwidth, polarization, array mutual coupling, and finite array edge effects are taken into account. Numerical simulations of an adaptive antenna that has multiple displaced phase centers indicate that near-field and far-field testing can be equivalent 相似文献