Ultra-Wideband Microstrip to Substrate Integrated Waveguide (SIW) Vertical Transition

an ultra-wideband vertical microstrip to substrate integrated waveguide (SIW) transitions is proposed for Three-dimensional (3-D) densification. The corner formed by the two different transmissions lines and electrical walls can easily transform the E-field of the dominant mode in the microstrip line to the SIW mode. An equivalent model based on the lumped element is proposed to estimate the initial parameters and to study the performances of the structure. Based on this model, two configurations are built. In the first configuration, the SIW line is on the same side of the microstrip line (MSL) and in the second one, it is integrated into the side of the ground plane. For experimental validation, two back-to-back prototypes MSL-SIW-MSL transitions are fabricated, with a SIW line acting as a bridge. The measured results agree well with those in the simulations, showing a return loss better than 10 dB over the entire 22 - 50 GHz frequency range with a maximum insertion loss of 1.8 dB.

I. Introduction

The densification is a core element in the next generation of millimeter-wave integrated systems, different types of technologies, processes, and transmissions lines (TL) are combined to reach the expected densification in the future system. A mass-production oriented process will be based on a three dimensional (3D) multilayer scheme with Monolithic Microwave Integrated Circuits (MMIC) and Low-Temperature Cofired Ceramics (LTCC) technologies [1]. High-Density Interconnects (HDI) will be used in the 3-D high integration scheme to ensure the interconnection of the different system components permitting a non-planar arrangement. The performance, size, and cost of the resulting system is dependent on the quality of these interconnections and transitions. In fact, the transition can generate discontinuities with a significant amount of radiation, reflection, and coupling. In addition, with increasing frequency, the crosstalk and electromagnetic interference increase due to the coupling between the close signal lines in the same and adjacent layers [2].