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In this letter, high-order mode dispersion of a novel spoof surface plasmon polariton (SSPP) unit cell is reported, which has excellent bandpass propagation feature. Its asymptotic frequency and intersection frequency with light line can be independently manipulated by changing the geometric parameters of the slot in proposed SSPP unit cell. In order to validate the feasibility of high-order mode of SSPPs applied in the design of bandpass filters, two SSPP waveguides based on the method with different bandwidths are fabricated and measured. No mode-conversion transition part is introduced in the procedure of waveguide design which avoids extra addition of layout area and reduces complexity of devices. The measurements show that the proposed SSPP waveguide based on high-order mode characteristics can achieve bandpass signal propagation smoothly with controllable bandwidth.
Liu et al. (Thu,) studied this question.