In this article, a novel beamforming patch array with a cosecant fourth power pattern is proposed for millimeter-wave synthetic aperture radar (SAR) applications. It enables radar receiving identical power in the field of view, provided that the radar cross section levels of targets within the illuminated area are similar. Different from “one-way” communication application, the SAR is a “two-way” system such that the received power is inversely proportional to R4R^{4} , not R2R^{2} , where RR is the distance between target and radar. Thus, conventional cosecant squared patterns are not suitable for SAR. Here, the concept and link properties of the proposed cosecant fourth power pattern are introduced, while its synthesis process is facilitated by a mixed optimization method, including nonlinear fitting and active pattern methods. As demonstrated, an array prototype, which consists of 12 series-fed patch subarrays and a substrate integrated waveguide network for power distributing and phase shifting, is designed and fabricated. Particularly, the power-distributing section only consists of symmetrical T-junctions with equal power division, thus making the antenna more tolerant to fabrication error. Good cosecant fourth pattern performance is achieved from 23.8 to 25.0 GHz. The presented array also owns the advantage of low profile ( ∼0.09λ0\sim 0.09\lambda _{0} ), compact, reliable, and low cost.

中文翻译：

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用于毫米波合成孔径雷达应用的具有余割四次幂模式的薄型波束成形贴片阵列


在本文中，提出了一种用于毫米波合成孔径雷达（SAR）应用的具有余割四次幂方向图的新型波束成形贴片阵列。只要照射区域内目标的雷达横截面水平相似，它就能使雷达在视场内接收相同的功率。与“单向”通信应用不同，SAR 是一个“双向”系统，接收功率与 R4R^{4} 成反比，而不是与 R2R^{2} 成反比，其中 RR 是目标与目标之间的距离雷达。因此，传统的平方余割图案不适合 SAR。在这里，介绍了所提出的余割四次方模式的概念和链接属性，同时通过混合优化方法（包括非线性拟合和主动模式方法）促进了其合成过程。如图所示，设计并制造了一个阵列原型，该原型由 12 个串联馈电贴片子阵列和一个用于功率分配和相移的基板集成波导网络组成。特别是，功率分配部分仅由具有等功率分配的对称T形结组成，从而使得天线对制造误差的容忍度更高。在 23.8 至 25.0 GHz 范围内可实现良好的余割第四方向图性能。所提出的阵列还具有薄型（∼0.09λ0\sim 0.09\lambda _{0}）、紧凑、可靠和低成本的优点。