An endfire antenna with sum and difference beams is designed based on phase transforming of a proposed asymmetric spoof surface plasmon polariton (SSPP) structure. The asymmetric arrays of grooves, with different groove depths, periods, and/or duty ratios, serve as transmission structure and transmit electromagnetic (EM) waves in SSPP modes. Due to the distinct phase constants for the EM fields on the two sides of the asymmetric structures, the transformation of phase difference for the EM waves is realized. Superposition in the endfire direction for the in-phase and out-of-phase EM fields forms the endfire radiations with sum and difference beams. A design procedure is proposed where operating frequencies of the endfire antenna are predicted with the dispersion curves of the asymmetric SSPP structures and allocated by phase transformation. A prototype is implemented to validate the proposed design principle. Sum beam operating frequencies of the endfire antenna are at 5.50, 6.60, and 7.09 GHz, while difference beams appear at 6.10 and 6.90 GHz. Good agreement of the results validates the feasibility of the proposed mechanism and design procedure. The proposed endfire antenna with sum and difference beams has broad prospect in direction finding, tracking, and anti-interference applications.

中文翻译：

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基于非对称欺骗表面等离子体激元的和差束端射天线相变

基于所提出的非对称欺骗表面等离子体激元 (SSPP) 结构的相变设计了具有和和差波束的端射天线。具有不同凹槽深度、周期和/或占空比的非对称凹槽阵列用作传输结构并以 SSPP 模式传输电磁 (EM) 波。由于非对称结构两侧的电磁场相位常数不同，实现了电磁波的相位差变换。同相和异相 EM 场在端射方向上的叠加形成具有和束和差束的端射辐射。提出了一种设计程序，其中使用非对称 SSPP 结构的色散曲线预测端射天线的工作频率，并通过相变分配。实施原型以验证所提出的设计原则。端射天线的和波束工作频率为 5.50、6.60 和 7.09 GHz，而差波束出现在 6.10 和 6.90 GHz。结果的良好一致性验证了所提出的机制和设计程序的可行性。所提出的和差波束端射天线在测向、跟踪和抗干扰应用中具有广阔的前景。