Slow‐Wave HMSIW‐SSPP Leaky‐Wave Antenna With Phase‐Shift Asymmetric Coupling for Continuous Beam Scanning

ABSTRACT A compact leaky‐wave antenna (LWA) with innovative phase‐shift asymmetric coupling for continuous beam scanning is presented. The antenna utilises a slow‐wave half‐mode substrate integrated waveguide with spoof surface plasmon polaritons (SW‐HMSIW‐SSPP) transmission line structure to achieve ultra‐compact dimensions in both longitudinal and lateral directions. The radiation characteristic is achieved using sinusoidal modulation on the SSPP structure. To enable continuous beam scanning through broadside, a novel and simple phase‐shift asymmetric coupling method is developed by placing sinusoidally modulated patches with π/2 phase shift on the metallised blind via‐hole arrays. This approach effectively suppresses the open stopband (OSB) and enables continuous beam scanning from backward to forward directions without radiation degradation at broadside. A prototype of the proposed LWA is fabricated and characterised. The measured results demonstrate that the antenna with 12 unit‐cells operates over a wide frequency range from 14.3 to 20.5 GHz with continuous beam scanning from −40° to +30°, while maintaining an ultra‐compact aperture of only 6.67 λ0 × 0.27 λ0.