A planar antenna is designed to replace complex structures of many rat-races and 90° hybrids used in conventional target detection antennas for receiving radar signals. The proposed antenna has 2 × 2 microstrip patch antenna arrays with dual feeding to radiate symmetric polarizations in the 9.375 GHz (X-band). The sum (Σ) pattern with circular polarization is implemented through a sequence feeding at port 1. The simultaneous feeding of port 2 radiates a difference (Δ) pattern in all linear polarizations. Thus, the proposed antenna is compact, planar, and has a simple comparator circuit. Measurement results verify the designed prototype, showing that the antenna has a null depth of over 34.5 dB in all polarizations, a peak sum gain 4.51 dB at 9.375 GHz, and a 3 dB axial-ratio bandwidth of 160 MHz.

中文翻译：

---

用于目标检测的带有双馈源微带贴片阵列的紧凑型双极化（CP、LP）

平面天线旨在取代传统目标检测天线中用于接收雷达信号的许多快速天线和 90° 混合天线的复杂结构。建议的天线具有 2 × 2 微带贴片天线阵列，具有双馈电以在 9.375 GHz（X 波段）辐射对称极化。圆极化的和 (Σ) 模式通过端口 1 的序列馈电实现。端口 2 的同时馈电在所有线性极化中辐射差异 (Δ) 模式。因此，所提出的天线是紧凑的、平面的，并且具有简单的比较器电路。测量结果验证了设计的原型，表明天线在所有极化中的零深度都超过 34.5 dB，在 9.375 GHz 时的峰值总和增益为 4.51 dB，以及 160 MHz 的 3 dB 轴向比带宽。