Polarimetric radar systems are beneficial to identifying and classifying targets but require multiple transmit or receive channels with different polarizations. This leads to a high hardware effort and thus higher costs. To use a single, linear polarized radar sensor as a polarimetric system, a frequency-dependent, polarization rotating reflector which can be placed in front of the radar antenna is presented. The reflector is based on a frequency selective surface (FSS) consisting of slot-excited substrate integrated waveguide (SIW) resonators. Resonator modes are analyzed and an equivalent circuit diagram to describe the filter functionality is developed. For using the described FSS as reflective structure, the design focuses on 45° oblique incidence. Different field vectors for normal and oblique incident angles are considered and different cavity modes for these cases are analyzed. An undesired mode is suppressed by an additional plated through via hole and slot impedances are matched. Reflector designs for normal and oblique incident angles are presented for 15 GHz (Ku-band) and afterward adapted to 35 GHz (Ka-band). The frequency band of operation with 12% fractional bandwidth is divided into two 4.5% subbands which allows a frequency-dependent polarization rotation of a linear polarized electromagnetic wave. Investigations on the fabrication accuracies are presented and reflectors for both bands are manufactured. Measurements are performed with a vector network analyzer and results fit well to the simulated curves. In the band of polarization rotation reflection, the matching is better than -13 dB and dielectric losses of less than 1 dB are achieved.

中文翻译：

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用于偏振雷达应用的基于 SIW 的偏振旋转反射器设计


偏振雷达系统有利于识别和分类目标，但需要多个具有不同偏振的发射或接收通道。这会导致较高的硬件工作量，从而导致更高的成本。为了使用单个线性偏振雷达传感器作为偏振系统，提出了一种可以放置在雷达天线前面的频率相关的偏振旋转反射器。该反射器基于频率选择表面 (FSS)，该表面由槽激励基板集成波导 (SIW) 谐振器组成。分析了谐振器模式，并开发了描述滤波器功能的等效电路图。为了使用所描述的 FSS 作为反射结构，设计重点是 45° 斜入射。考虑法向和倾斜入射角的不同场矢量，并分析这些情况下的不同腔模式。通过额外的电镀通孔抑制不需要的模式，并匹配槽阻抗。针对 15 GHz（Ku 频段）提出了法向和倾斜入射角的反射器设计，随后适用于 35 GHz（Ka 频段）。具有 12% 分数带宽的工作频段被分为两个 4.5% 子带，允许线性偏振电磁波进行频率相关的偏振旋转。对制造精度进行了研究，并制造了两个波段的反射器。使用矢量网络分析仪进行测量，结果与模拟曲线非常吻合。在偏振旋转反射频段，匹配优于-13 dB，介电损耗小于1 dB。