A Method for Fast Extracting the Phase Constant of Periodically Depth-Modulated Spoof Surface Plasmon Polaritons Leaky-Wave Antenna

In this letter, periodically-depth-modulated (PDM) leaky-wave antennas (LWAs) employing Spoof Surface Plasmon Polaritons (SSPP) waveguides are studied. A universal method, based on network theory, is therefore proposed herein to intuitively analyze and accurately predict the phase constant of SSPP-based LWAs. In order to obtain the LWA dispersion relation, each leaky wave period is assumed to be equivalent to a section of transmission line. In parallel, the ABCD matrix of each unit is then calculated based on its wave number and characteristic impedance. Under the cascade connection law, the ABCD matrix of one LWA period and the phase constant of the PDM SSPP LWA are theoretically obtained. The dispersion curves of arbitrarily PDM SSPP LWAs are consequently intuitively established by using the proposed method. To validate the theory, as examples, three typical PDM SSPP LWAs, including one ideal and two planar PDM SSPP LWAs, are analyzed. The calculated dispersion curves are shown to accurately predict the LWAs' performance, thereby demonstrating the validity and universality of the proposed method. In addition, the simulated results for the PDM planar SSPP LWAs agree well with those from measurements.