Broadband directional Moreno coupler for high-performance air-filled SIW-based Substrate Integrated Systems
Résumé
A broadband directional Moreno coupler consisting of a high performance Air-Filled Substrate Integrated Waveguide (AFSIW) coupled to a top Dielectric-Filled Substrate Integrated Waveguide (DFSIW) is introduced. It is intended for high performance and low-cost millimeter-wave substrate integrated systems based on multilayer Printed Circuit Board (PCB) process. The bottom layer may make use of an extremely low-cost standard substrate such as FR-4 on which base-band or digital circuits can be implemented so to obtain a self-packaged and compact millimeter-wave integrated system. Design of the proposed Moreno coupler is detailed. To the authors' knowledge, it is the first time that a Moreno coupler based on different dielectric-loaded waveguides is reported. It is also the first proposed AFSIW device taking advantage of a multilayer structure and the first AFSIW directional coupler reported in the literature. For demonstration purposes, a broadband 20 dB coupler operating over Ka-band has been designed and fabricated. It achieves a measured insertion loss, coupling and isolation of 0.6 ±0.2 dB, 18.7 ±1.3 dB and 44.7 ±13.7 dB, respectively. This coupler is of particular interest for monitoring applications, for example, in radar transmitters.