Half-Mode Slab Air-Filled Substrate Integrated Waveguide (SAFSIW)

This paper reports the proposal and development of a half-mode slab air-filled substrate integrated waveguide, a solution of compromise between half-mode air-filled substrate integrated waveguide (SIW) and half-mode SIW. Theoretical analysis and simulated results are presented to understand the operation mechanism. For experimental validation, a transition to SIW is reported and used in a back-to-back configuration. With low-cost FR-4 to cover the structure, the measured results show an insertion loss of 1.1 ± 0.17 dB together with a reflection coefficient better than −21.5 dB over the entire Ka-band. Using two transmission lines of different lengths, an attenuation of 0.298 dB/cm is obtained at 33 GHz. The half-mode slab air-filled SIW provides high degrees of freedom to control the attenuation and phase constants for the design of microwave and millimeterwave components including couplers and leaky-wave antennas.