An S‐shaped planar antenna (SPA) with a bidirectional radiation pattern and beam tilt characteristic is proposed to achieve maximum communication distance for helmet applications. The proposed SPA is comprised of an S‐shaped radiation strip (consisting of a microstrip meander line and two main arms with two inverted L‐shaped parasitic elements) and a rectangular ground plane, where a simplified microstrip power divider is introduced by modifying the feed structure in the center of the SPA, such that the S‐shaped radiation strip works in the second resonant mode. The proposed SPA generates a tilted beam in the E‐plane with an angle of 45°, which is attributed to the obliquely staggered arms of the antenna at a distance. By introducing inverted L‐shaped parasitic elements at the end of the two arms, the directivity of the bidirectional radiation pattern can be further improved, thereby increasing the antenna gain. The working principle is analyzed theoretically, and the effects of the antenna structural parameters on the radiation pattern are also analyzed. The experimental results indicate that the 3:1 VSWR impedance bandwidth is 120 MHz, with a realized peak gain of 1.5 dBi at 2.45 GHz. The proposed antenna is designed for real‐world applications, allowing the antenna to be obliquely installed while keeping the peak gain direction horizontal for maximum communication distance.

中文翻译：

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具有45°倾斜双向辐射方向图的S形平面天线，用于摩托车头盔

提出了一种具有双向辐射方向图和波束倾斜特性的S形平面天线（SPA），以实现头盔应用的最大通信距离。拟议的SPA由一个S形辐射带（由一条微带弯折线和两个带有两个倒L形寄生元​​件的主臂组成）和一个矩形接地平面组成，其中通过修改馈源引入简化的微带功率分配器SPA中心的结构，使得S形辐射带在第二共振模式下工作。拟议的SPA在E平面内产生一个45度角的倾斜波束，这是由于天线在一定距离处倾斜交错而产生的。通过在两个臂的末端引入倒置的L形寄生元​​件，双向辐射图的方向性可以进一步提高，从而提高天线增益。从理论上分析了工作原理，并分析了天线结构参数对辐射方向图的影响。实验结果表明，3：1 VSWR阻抗带宽为120 MHz，在2.45 GHz时实现的峰值增益为1.5 dBi。建议的天线是为实际应用而设计的，允许倾斜安装天线，同时保持峰值增益方向为水平，以实现最大通信距离。1 VSWR阻抗带宽为120 MHz，在2.45 GHz时实现的峰值增益为1.5 dBi。建议的天线是为实际应用而设计的，允许倾斜安装天线，同时保持峰值增益方向为水平，以实现最大通信距离。1 VSWR阻抗带宽为120 MHz，在2.45 GHz时实现的峰值增益为1.5 dBi。建议的天线是为实际应用而设计的，允许倾斜安装天线，同时保持峰值增益方向为水平，以实现最大通信距离。