Easy-to-assemble and high quality-factor ESIW filter with post-based soldered inverters in X-band

Abstract

Empty Substrate Integrated Waveguide (ESIW) devices maintain a compromise between the advantages of classical waveguide technologies, such as high quality factor and low losses, and the advantages of planar ones, like low cost and easy compact integration. Compared with SIW, since ESIW is not dielectric filled, additional advantages are achieved, such as lower insertion losses and resonators with higher quality factor. In recent years several filters and folded filters have been designed in ESIW, using all of them resonators based on irises. An alternative to the use of irises is H-plane cylindrical posts. Although cylindrical posts have been widely used in other technologies like Rectangular Waveguide, SIW or AFSIW, it is the first time that this kind of inverters has been used in ESIW. In this paper, the use of posts in ESIW is proposed and validated through the design and manufacture of a bandpass filter in X-band. Posts are soldered to top and bottom layers after ESIW is assembled, being this kind of filters easier to manufacture and more robust than those based on irises. The designed filter achieves return losses higher than 12 dB and insertion losses lower than 1.6 dB (considering microstrip-to-ESIW transitions) and a quality factor of 918.74.