Improved Microstrip-to-ESIW Transition With Elliptical Dielectric Taper in Ku- and Ka-Bands

Abstract

Empty Substrate Integrated Waveguide (ESIW) technology preserves the many advantages of the Substrate IntegratedWaveguide (SIW) such as low cost, low profile, and easy integration with Printed Circuit Boards (PCBs). Moreover, it has additional advantages due to the avoidance of dielectric filling: lower insertion losses and resonators with higher quality factor. In order to connect the ESIW line to classical planar lines, the design of transitions becomes specially important. Due to this, some microstrip-to-ESIW transitions have been published in recent years. Problems of these transitions are usually the complexity of the manufacturing process or increased radiation losses. Knowing the aforementioned disadvantages of the published solutions, in this paper, the transition with an expanded ESIW section has been improved, by adding an easy-to-manufacture dielectric taper that minimizes the undesired radiation losses. Additionally, the new proposed transition can be mechanized easier than previous solutions based on sharp tapers. Moreover, the slight overlap between the microstrip line and the upper ESIW metal cover has been avoided, thus enhancing the return losses of the proposed transition. To validate the proposed transition, two back-to- back prototypes have been manufactured both in Ku- and Ka-band, obtaining insertion losses lower than 0.31 dB and return losses higher than 20.8 dB in Ku-band, and insertion losses lower than 1.36 dB and return losses higher than 14.75 dB in Ka-band.