A single-layer microstrip patch antenna (MPA) under the operation of TM10 and TM20 modes for pattern diversity application without needing to rely on any feeding network is proposed for the first time in this letter. Initially, when a thorough analysis on mode excitation and inhibition of the MPA was deeply conducted, it demonstrated that its TM10 and TM20 modes could be independently excited by properly placing two coaxial ports underneath the radiating patch; thus, generating the desired broadside and bidirectional radiation patterns, respectively. Then, two sets of shorting pins are inserted below the core radiator, aiming to raise the resonant frequency of its TM10 mode in proximity to that of the TM20 mode. In addition, the maximum input resistances of these dual radiative modes decrease dramatically as f10 and f20 increase, which enables good impedance matching. Finally, the proposed MPA is designed, fabricated, and tested to validate the working principle. The results illustrate that this antenna can operate over the overlapping frequency ranges of 5.83–5.89 GHz with an envelope correlation coefficient of lower than 0.015, while keeping its low-profile thickness of 0.045λ0. Due to its unique advantages of low profile, simple structure, and good diversity, the proposed MPA could be a promising option in wireless local area network (WLAN)-related applications.

中文翻译：

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用于模式分集应用的无馈电网络的单层双模微带天线

在这封信中首次提出了一种在TM10和TM20模式下工作的单层微带贴片天线（MPA），用于方向图分集应用而无需依赖任何馈电网络。最初，当对MPA的模式激发和抑制进行深入分析时，表明通过在辐射贴片下方适当放置两个同轴端口可以独立激发其TM10和TM20模式；因此，分别生成所需的宽边和双向辐射模式。然后，在核心辐射器下方插入两组短路销，旨在将其TM10模的谐振频率提高到接近TM20模的谐振频率。此外，这些双辐射模式的最大输入电阻随着 f10 和 f20 的增加而急剧下降，这可以实现良好的阻抗匹配。最后，所提出的 MPA 被设计、制造和测试以验证工作原理。结果表明，该天线可以在 5.83–5.89 GHz 的重叠频率范围内工作，包络相关系数低于 0.015，同时保持其 0.045λ0 的低剖面厚度。由于其低剖面、结构简单和良好的多样性的独特优势，所提出的 MPA 可能是无线局域网 (WLAN) 相关应用中的一个有前途的选择。同时保持其 0.045λ0 的薄型厚度。由于其低剖面、结构简单和良好的多样性的独特优势，所提出的 MPA 可能是无线局域网 (WLAN) 相关应用中的一个有前途的选择。同时保持其 0.045λ0 的薄型厚度。由于其低剖面、结构简单和良好的多样性的独特优势，所提出的 MPA 可能是无线局域网 (WLAN) 相关应用中的一个有前途的选择。