Coaxial resonators are fundamental components in RF and microwave systems, widely used in filters, oscillators, and precision measurement equipment due to their high Q factors and excellent shielding properties. In this blog, we demonstrate how to use the Eigenmode solver in Ansys HFSS by analyzing a silver-plated coaxial resonator. The example highlights how the solver computes both the resonant frequency and Q factor.
Simulation Workflow
This example uses an imported coaxial rectangular cavity, with the cavity walls defined as silver using a finite conductivity boundary condition with σ = 6.1 × 10⁷ S/m.
The Eigenmode solver does not require any defined sources, you specify the number of modes to compute and the convergence criteria. In this case, the minimum frequency is set to 1.1 GHz, and only the first mode is calculated. The convergence criteria are shown below.
To ensure maximum accuracy, curvilinear elements were applied, and the initial mesh resolution was increased under HFSS > Mesh > Initial Mesh Settings.
Once the solution is complete, the results can be accessed by right-clicking Setup1 under Analysis in the Project Manager and selecting Eigenmode Data. This opens the Solutions dialog on the Eigenmode Data tab, where the computed resonant frequency and Q factor are displayed. Additional information is available under the Profile, Convergence, and Mesh Statistics tabs.
The results can also be displayed in a tabular report by right-clicking Results in the Project Manager and selecting Create Eigenmode Parameters Report > Data Table. In this example, output variables were created to facilitate result extraction and visualization.
Also, a plot of the frequency and Q values for each solution pass up to convergence can be created under Results in the Project Manager.
Color contour plots of the electric and magnetic fields on the cross section can be generated by selecting the YZ plane and right-clicking Plot Fields > E > Mag_E. The plots will appear under Field Overlays in the Project Manager. To display the mesh on the same cross section, select the YZ plane and click Plot Mesh.
E Field H Field Solution Mesh
The video below walks through these steps in detail, and the model shown is available in the downloadable resources.
Downloadable Resources
Coaxial Resonator Model
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