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

• Published in: International journal of circuit theory and applications 2022-02, Vol.50 (2), p.507-524
• Main Authors: Ertay, Agah Oktay, Simsek, Serkan
• Format: Article
• Language: English
• Subjects: AFGSM; asymmetrically loaded helix; Comparative studies; Computer simulation; coupled mode theory; Coupled modes; Equivalent circuits; Frequency ranges; helix slow wave structure (SWS); helix traveling wave tube (TWT); Microstrip transmission lines; periodic structures; Representations; S matrix theory; Slits
• ISSN: 0098-9886; 1097-007X
• DOI: 10.1002/cta.3138

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. One of the main goal of this study is to present analysis and design of band edge frequencies of dielectric loaded helix slow wave structures (SWSs) by using theirs equivalent circuit models. Another important point of this paper is to apply effective rod model to different dielectric loaded helix SWSs to perform circuit model for the first time. The Auxiliary Functions of Generalized Scattering Matrix (AFGSM) method has a faster computation time with respect to other conventional methods.