Guiding Surface Waves With Low-Loss by Planar Transverse Resonance and Application to Leaky Wave Antennas

This article presents a new surface-wave guiding method based on horizontal transverse resonance, enabling strong lateral confinement of surface waves (SWs) using only simple metallic discontinuities on a planar dielectric substrate. Unlike traditional surface-wave guides (SWGs) - such as spoof surface plasmon polaritons (SSPPs) and effective-index structures - our proposed configuration does not require vias, drilled air holes, or subwavelength patterning, thereby offering low fabrication complexity and a very low profile. Newly developed analytical modeling using the finite-difference frequency-domain (FDFD) approach confirms that the appropriately positioned metal discontinuities act as effective electric sidewalls, producing a family of TM and TE modes with controllable dispersion and exceptionally low substrate leakage. Near-field measurements confirm the predicted transverse resonance and verify strong confinement compared with an unbounded grounded dielectric slab (GDS). Two practical applications are then developed. First, a leaky wave antenna (LWA) is realized by periodically perturbing the SWG, achieving single-sided radiation with continuous backward-to-forward quadrant frequency scanning. Second, a dual-layer implementation is introduced to support a dominant TE SW mode, yielding conductor losses as low as 0.02 dB/m at 100 GHz - significantly outperforming microstrip, SIW, and planar Goubau lines (PGLs). Together, these results establish the transverse resonance-based TM and TE SWGs as a promising new platform for low-loss millimeter-wave (mmWave) transmission and high-performance LWAs.