Abstract
Planar Goubau lines show promise as high frequency, low-loss waveguides on a substrate. However, to date only numerical simulations and experimental measurements have been performed. This paper analytically investigates the surface wave mode propagating along a planar Goubau line consisting of a perfectly conducting circular wire on top of a dielectric substrate of finite thickness but infinite width. An approximate equation for the propagation constant is derived and solved through numerical integration. The dependence of the propagation constant on various system parameters is calculated and the results agree well with full numerical simulations. In addition, the spatial distribution of the longitudinal electric field is reported and excellent agreement with a numerical simulation and previous studies is found. Moreover, validation against experimental phase velocity measurements is also reported. Finally, insights gained from the model are considered for a Goubau line with a rectangular conductor. The analytic model reveals that the propagating mode of a planar Goubau line is hybrid in contrast to the transverse magnetic mode of a classic Goubau line.
Highlights
Surface waves (SW) on circular conducting wires have been of theoretical interest since their discovery by Sommerfeld[1]
It represents an alternative to standard substrate transmission lines namely the microstrip line and as such multiple essential electronic components have been devised for the planar Goubau line (PGL) including broadband loads, power dividers and frequency selective filters[14,15,16]
This paper presents a theoretical investigation of a planar Goubau line consisting of a cylindrical wire above an infinitely wide substrate
Summary
Surface waves (SW) on circular conducting wires have been of theoretical interest since their discovery by Sommerfeld[1]. These coated wires, named Goubau lines in later years, showed low loss and weak dispersion They were discussed as an alternative to traditional, two-conductor transmission lines. By introducing sub-wavelength corrugations, spoof surface plasmon polaritons emerge which have tunable properties and can exhibit sub-wavelength lateral c onfinement[5,6,7] These new technologies have been discussed as solutions to problems such as signal integrity in integrated circuits and backhaul solutions for the network standard 5 G8,9. In many cases it is favourable to print a conductor design on a substrate using established printed circuit board fabrication processes such as etching This led to the invention of a planar Goubau line (PGL) consisting of a thin rectangular conducting strip on a substrate[10,11,12,13]. All materials are assumed to be non-magnetic and have permeability equal to the magnetic constant μ0
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