This letter presents a compact cavity-backed slot antenna using dual mode for Internet of Things (IoT) applications. The proposed antenna has stub structures for generating additional resonant mode, by which two polarization components orthogonal to each other are realized within the impedance bandwidth. By the combination of the two modes, circularly polarized radiation is generated. The impedance bandwidth increase by the additional resonant mode, and the proposed stub structures act as a capacitive loading contributing to the miniaturization of the antenna. For validation of the proposed antenna, simulations were conducted, and the antenna was fabricated and measured. The fabricated antenna size is 0.23 $\lambda _{0}$ $\times\; 0.23\lambda _{0}$ $\times\; 0.04\lambda _{0}$ , showing a significantly compact size compared to the conventional structures. The measured results confirm that the antenna has a impedance bandwidth from 896 to 958 MHz, and 3 dB axial ratio (AR) bandwidth is about 5 MHz. The measured peak gain and AR at 915 MHz are 2.4 dBic and 0.6 dB, respectively.

中文翻译：

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用于物联网应用的采用双模的紧凑型腔体后背缝隙天线

这封信提出了一种用于物联网（IoT）应用的使用双模式的紧凑型背腔缝隙天线。所提出的天线具有用于产生附加谐振模式的短截线结构，通过该短截线结构，在阻抗带宽内实现了彼此正交的两个极化分量。通过两种模式的组合，产生了圆偏振辐射。阻抗带宽通过附加谐振模式而增加，并且所提出的短截线结构充当电容负载，有助于天线的小型化。为了验证所提出的天线，进行了仿真，然后制造并测量了天线。制作的天线尺寸为0.23 $ \ lambda _ {0} $ $ \ times \; 0.23 \ lambda _ {0} $ $ \ times \; 0.04 \ lambda _ {0} $ 与传统结构相比，尺寸显着紧凑。测量结果证实该天线具有从896到958 MHz的阻抗带宽，并且3 dB的轴向比率（AR）带宽约为5 MHz。在915 MHz处测得的峰值增益和AR分别为2.4 dBic和0.6 dB。