Optimal transition in Air-filled Substrate Integrated Waveguide

Air-filled Substrate Integrated Waveguide (SIW) based on multilayer Printed Circuit Board (PCB) process is studied in this paper for millimeter-wave applications. To allow interconnects of the proposed Air-filled SIW with Substrate Integrated Waveguide (SIW), a wideband transition is needed. This paper presents an assessment of transition of dielectric SIW toward an air-filled SIW with various design shapes of taper in order to evaluate the losses in the structure. The shape of taper is designed accordingly to the equation for taper consisting of linear, exponential, raised cosine and parabolic. At Ka-band it is shown that raised cosine taper based on Rogers RT/Duroid 6002 has a better return loss lower than 20 dB, with transmission loss of 0.16±0.02 dB from 28 to 40 GHz. For the U-band, the raised cosine taper based on Rogers RT/Duroid 6002 also has a better return loss lower than 40 dB and the transmission loss is 0.3±0.01 dB from 44 to 60 GHz, respectively. For validation purposes, a back-to-back transition is simulated. It achieves a return loss of better than 20dB and a transmission loss of 0.35±0.05dB from 28 to 40 GHz. Then, a return loss of better than 40 dB and transmission loss of 0.75±0.05dB from 44 to 60 GHz.