Detection of band edge frequencies in symmetric/asymmetric dielectric loaded helix slow‐wave structures

Abstract

The significant contribution of this paper is to present a comprehensive analysis and design of π-point and band edge frequencies of reported helix SWSs including not only a microwave but also millimeter-wave operation frequencies considering the methods in available literature which are the Coupled Mode Analysis (CMA), the Exact Floquet Approach (EFA), and the Auxiliary Functions of Generalized Scattering Matrix (AFGSM) as a comparative study. A different approach called as effective rod model is applied to circular/ T-shaped dielectric support rod helix SWSs in order to obtain ladder circuit representation of one turn of related helix SWSs for the first time. Scattering matrices of equivalent circuit representation of interested helix SWSs are obtained by using microstrip line model of helix SWS which slits helical tape at the effective helix radius along the direction normal to the helix winding direction and flattens it out for the EFA, the AFGSM, and the CMA methods. Additionally, comparisons are given for investigated methods together with the results of Computer Simulation Technology (CST) design environment, and good agreement has been observed among numerical results of different helix SWSs in a broad frequency range.

Investigation of AFGSM Methods for Some Electromagnetic Bandgap Structures: From Analysis to Applied Antenna Design

“…The theory of the AFGSM method is based on the analysis of stored complex power (Ψ) in the unit cell of the periodic structure [33], [39]. It is important to note that the AFGSM method can detect the band edge frequencies by using one of the most crucial advantages of the fact that monitoring zero transitions of Ψ can precisely provide exact positions of bandgap regions [33].…”

“…In Equation ( 23), K 1 and K −1 equal to (1 − S 21 )/(S 22 ) and (−1 − S 21 )/(S 22 ), respectively. When a symmetric unit cell is considered in a single Floquet mode region, the following equation can be written as given in [33], [39]…”

“…This powerful method converts the dispersion problem into a rootfinding problem. The AFGSM method can be utilized to find bandgaps of the periodic structures without solving an eigenvalue equation [33], [38], [39]. In this case, a method emerges that can significantly size reduction of the computational effort required for planar electromagnetic bandgap structures.…”