Slow Wave Substrate-Integrated Waveguide With Miniaturized Dimensions and Broadened Bandwidth

A novel slow wave (SW) substrate-integrated waveguide (SIW) with enhanced SW factor (SWF) and broadened bandwidth is proposed by simultaneously increasing the effective permeability and permittivity. The effective permittivity is increased by the enhanced capacitance between the top plane of the waveguide and the loaded patches which are shorted to the SIW bottom plane by the blind via-holes. The effective permeability is increased by lengthening the current path by adding patches on the blind via-holes. The proposed SW-SIW with simultaneous increased effective permeability and permittivity has two obvious advantages over the reported SW-SIW with only effective permeability or permittivity increased: 1) smaller longitudinal and lateral dimensions resulted from higher SWF and lower cutoff frequency, respectively, and 2) wider bandwidth due to stable wave impedance along the periodical SW structure. The lateral dimension of the proposed SW-SIW is decreased by 53% compared with the normal SIW with the same cutoff frequency. The phase velocity is decreased by 73%, which means the longitudinal length is reduced by 73% consequently. The operation band is 7.0–18.8 GHz (91.5% fractional bandwidth) covering ${X}$ - and Ku -bands. A prototype of the proposed SW-SIW is manufactured and measured, and the measured results agree well with the simulations.