Versatile, Error-Tolerant, and Easy to Manufacture Through-Wire Microstrip-to-ESIW Transition

Empty substrate integrated waveguide (ESIW) technology preserves the many advantages of the SIW, such as low cost, low profile, or integration in a printed circuit board. But, since the fields propagate through the air in the ESIW instead of propagating through a lossy dielectric as in the SIW, the ESIW presents lower losses and higher quality factors in resonators. Several transitions have been recently proposed in the literature that connect the ESIW to a classical planar line such as the microstrip. In all these transitions, both the feeding planar lines and the ESIW are built in the same substrate layer (the height of the ESIW cannot be selected independently), and they are based on tapered structures in the planar line and/or in the ESIW that reduce the compactness of the transition. These transitions also combine metallized and nonmetallized parts, which increases the complexity of the manufacturing process. In this article, a new through-wire microstrip-to-ESIW transition is proposed. The feeding lines and the ESIW are implemented in different layers so that the height of the ESIW can be independently chosen, and higher quality factor ESIW filters can be excited. Besides, this novel transition can be manufactured with simple cuts and with uniform metallization so that the manufacturing complexity is reduced. Finally, it is a very compact transition that can be freely rotated; that is, the angle between the feeding lines and the ESIW does not affect the performance of the transition. This provides a high degree of versatility in the design phase.