Broadband transition from dielectric-filled to air-filled Substrate Integrated Waveguide for low loss and high power handling millimeter-wave Substrate Integrated Circuits

摘要

Air-filled Substrate Integrated Waveguide (SIW) based on multilayer Printed Circuit Board (PCB) process is proposed in this paper for millimeter-wave applications that require low cost, high performances and compactness. This air-filled SIW allows for substantial loss reduction and power handling enhancement. Its fabrication involves three layers. The top and bottom substrates can consist of a low cost standard substrate such as FR-4 on which base-band or digital circuits can be implemented so to obtain a very compact, high performance and low cost millimeter-wave system. At Ka-band, it is shown that air-filled SIW compared to dielectric-filled SIW based on Rogers RT/Duroid 5880 and 6002 reduces losses by a mean value of 0.054 dB/cm and 0.11 dB/cm and increases average power handling capability by 6 dB and 8 dB, respectively. To allow interconnects of the proposed air-filled SIW with dielectric-filled SIW, a broadband transition is presented. The design steps of this transition are detailed. For demonstration purposes, a back-to-back transition operating over the Ka-band is fabricated. It achieves a matching of better than −15 dB and an insertion loss of 0.6 ±0.2 dB (0.3 ±0.1 dB for the transition) from 27 to 40 GHz.