Radiation losses in Substrate Integrated Waveguides: A semi-analytical approach for a quantitative determination

Substrate Integrated Waveguides, an emerging technology for microwave and mm-wave circuits, are affected by three loss mechanisms: Ohmic and dielectric, as standard waveguides, and radiation. While for Ohmic and dielectric losses equations to determine the expected deterioration are available, for radiation loss no quantitative relationship was derived. This paper presents a semi-analytical approach to predict the attenuation constant due to radiation loss in Substrate Integrated Waveguides.

I. Introduction

Substrate Integrated Waveguide (SIW) technology offers a suitable approach to design and manufacture microwave and mm-wave circuits [1]. A typical SIW transmission line, shown in Fig. 1, is based on a dielectric slab and it supports the propagation of the electromagnetic field according to a distribution that is well approximated by modes. The field is confined using a top and a bottom metal plates and two rows of metalized vias. The propagation of the modes, in particular the fundamental mode, is affected by three different loss mechanisms: Ohmic, dielectric and radiation losses. Ohmic and dielectric losses also affect standard waveguides, even if for SIW circuits these two losses are usually larger because of the reduced waveguide height and because of the large losses (if compared to air) of the dielectric slab, respectively. On the other side, radiation loss is a typical aspect of SIW circuits [2].