Accurate Modeling of Conductor Rough Surfaces in Waveguide Devices

Abstract

To address the effects of surface roughness on wave propagation in the microwave and millimeter-wave bands, this paper studies electromagnetic wave propagation and focuses on the propagation loss within an inner environment featuring surface roughness of the metallic waveguide structures. The conductivity gradient model is first developed to treat surface roughness with inhomogeneous conductivity, and then the concept of a frequency-dependent effective conductivity is introduced to model the effects of surface roughness in waveguide structures. With the effective conductivity used in the commercial 3D field solver, High Frequency Structure Simulator (HFSS™), a surface impedance boundary condition strategy is applied on ideally smooth surfaces to model the actual behavior of rough metallic waveguide surfaces. Finally, the propagation performance is predicted by comparing the effects of surface roughness in metallic waveguide structures and the results from the models with ideally smooth surfaces, using rectangular waveguide, cylindrical resonator and coupling cavity filters models. Overall, this effective conductive concept can be applied using various commercial field solvers to handle surface roughness effects accurately and efficiently in any work involving conducting microwave structures.

Compact Wideband Groove Gap Waveguide Bandpass Filters Manufactured with Printing and CNC Milling Techniques

“…This is because the surface roughness of the 3-D printed prototypes has a negative effect on the conductor loss of the silver and conductive paint thick layers. The roughness of the metallized surfaces is larger than the one obtained with the CNC technique [36], [37], and consequently the attenuation increases. Besides, the conductive paint has a poor conductivity (𝜎 10 S/m , which is approximately 2800 times lower than the value of the 6082 aluminum.…”

Low-Cost Direct-Writing of Silver-Based Ink for Planar Microwave Circuits up to 10 GHz

“…This can be explained if the surface roughness of the conductor surface is taken into account. Effective conductivity, 𝜎 , is a concept which is defined as the conductivity of a conductor with ideally smooth surface that would result in the same loss as the rough surface [47]. Although effective conductivity decreases with increasing frequency, using an average value of 2×10 6 S/m yields consistent results with RF simulations above 500 MHz.…”

Dielectric response and polarization mechanism of alkali silicate glasses in gigahertz to terahertz frequency range

“…A candidate dielectric material for use in filters is oxide glass, 9–11 which possesses a low dielectric constant, low dielectric loss in the high‐frequency range, and high heat resistance. Suitable dielectric materials must also have high surface quality to minimize the skin effect, which means that the current density is high near the surface of the conductor such that conduction loss increases at high frequencies 12 . High quality flat surfaces are easy to obtain with oxide glasses, which makes them suitable for use in LTCC filters.…”

“…Suitable dielectric materials must also have high surface quality to minimize the skin effect, which means that the current density is high near the surface of the conductor such that conduction loss increases at high frequencies. 12 High quality flat surfaces are easy to obtain with oxide glasses, which makes them suitable for use in LTCC filters. However, their dielectric properties in the gigahertz to terahertz (GHz-THz) region have not been fully investigated.…”