Expertise: equivalent circuits of waveguide discontinuities
Leonardo Zappelli is working on the representation of waveguide discontinuities exciting evanescent accessible modes. The key feature of the equivalent circuit is its capability for simplification if a port relative to an accessible evanescent mode is matched, or connected to a very long line. Circuit drawing is simple, fast and based on a regular polygon with as many susceptances as the sides and the diagonals. Each side is connected with a line to the terminal ports and, if the port refers to an evanescent accessible mode, a series reactance is added. This reactance is the key to the evanescent part of the circuit because it is able to cancel the effect of the evanescent mode if the relative port is matched or connected to a very long evanescent line, reducing the complexity of the circuit by one degree. With the help of the proposed equivalent circuit, we can define some approximating functions for the elements of a circuit representing a post or an iris in a waveguide, which can be used to speed up the optimization of complex structures, like filters or diplexers, based on posts or irises. Another activity regards dielectric and metallic frequency selective surface.
Leonardo Zappelli received his Laurea Degree in Electronics Engineering (Summa cum Laude) from the University of Ancona in 1986. Since 1987 he was with the University of Ancona (now Polytechnical University of Marche) and at present he is an Assistant Professor within the scientific sector ING-INF/02 (Electromagnetics). At the Polytechnical University of Marche, he is the teacher for the courses of “Foundation of Electromagnetics”, (Laurea in Electronics Engineering). His scientific activity has concerned several aspects of the electromagnetic area, with special emphasis on microwaves, electromagnetic compatibility, phased array antennas and frequency selective surfaces.