This article presents a compact, pattern-reconfigurable leaky-wave antenna (LWA) realized on a dual-path spoof surface plasmon polariton (SSPP) transmission structure, wherein two PIN diode switches control the active propagation path to enable three independently configurable radiation modes. In Mode 1 (S1 ON, S2 OFF), the upper SSPP branch operates alone and produces a right-handed circularly polarized (RHCP) beam scanning over a 22^◦ range within 8.3–9.0 GHz with an average gain of approximately 7.5 dBi and a radiation efficiency exceeding 92%. In Mode 2 (S1 OFF, S2 ON), the structurally symmetric lower branch is activated instead, yielding an identical scanning performance with left-handed circular polarization (LHCP). In Mode 3 (S1 ON, S2 ON), both branches are simultaneously energized, producing a linearly polarized (LP) beam that scans over a wider 78^◦ angular span within 8.3–10.3 GHz and achieves a peak gain of 10.3 dBi together with a total efficiency greater than 70%. Sidelobe levels are suppressed below −10 dB across all three modes by means of a tapered arrangement of elliptical patches loaded periodically along the transmission line. The antenna operates over a broadband range of 5–15 GHz and occupies a compact footprint of 216 × 40 mm2. The proposed design offers an attractive combination of wide-bandwidth operation, high gain, low sidelobe levels, and flexible polarization switching that is well-suited to radar sensing, satellite communication, and next-generation wireless systems.

Index Terms—Spoof surface plasmon polariton (SSPP), leaky-wave antenna (LWA), reconfigurable antenna, beam steering, PIN diode switching, low sidelobe level (SLL), circular polarization, linear polarization.