A single-layer, dual-mode microstrip patch antenna with self-nulling patterns is proposed. The antenna consists of a circular microstrip patch antenna, surrounded by a shorted concentric ring patch, exciting the TM11 and TM21 modes, respectively. Adaptive radiation patterns with self-scanning and nulling capabilities are realized by concomitantly exciting these two modes. To attain the mode purity, four symmetrical arc slits, inspired by the surface current distribution of the TM21 mode, as well as two horizontal slits are placed in the ring patch. For the miniaturization purpose, the circular patch is loaded by three vertical slits. A prototype of the proposed antenna is fabricated and tested. The measured results are in good agreement with the simulation results. To showcase the effectiveness of the proposed self-nulling dual-mode antenna, it is employed as an antenna element in a linear scanning array with element spacing greater than one-wavelength to reduce its unwanted grating lobes.

中文翻译：

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一种用于降低栅瓣的自归零单层双模微带贴片天线

提出了一种具有自归零模式的单层双模微带贴片天线。天线由圆形微带贴片天线组成，周围环绕着短路的同心环贴片，分别激发 TM11 和 TM21 模式。通过同时激发这两种模式来实现具有自扫描和归零能力的自适应辐射模式。为了获得模式纯度，受 TM21 模式表面电流分布启发的四个对称弧形狭缝以及两个水平狭缝被放置在环形贴片中。出于小型化的目的，圆形贴片由三个垂直狭缝加载。所提出的天线的原型被制造和测试。实测结果与仿真结果吻合较好。为了展示所提出的自归零双模天线的有效性，