Learning Forum

[Ronny Roy]

How to find resonant frequencies of a dielectric structure using HFSS' Transient solver with broadband excitation? Can you please provide step-by-step instructions for the same?

[GioF]

Hi,

It is recommended to use the Eigenmode solver for finding the resonance frequencies of a structure and the fields at those frequencies. Eigenmodes are the resonances of the structure. With Eigenmode solver you will be able to calculate all of the resonance frequencies, as well as the Q factor of each frequency. 

You can find more technical information on calculating resonant frequencies on HFSS Help under,
HFSS Help> HFSS Technical Notes> The HFSS Solution Process> Calculating the Resonant Frequency
and
HFSS Help> HFSS Technical Notes> The HFSS Solution Process>Q Factor of Resonant Cavities

You can find more information on adding an Eigenmode Solution Setup in, Ansys HFSS 2023 R1 - Adding an Eigenmode Solution Setup

[Ronny Roy]

I have used eigenmode solver. I want to find resonant frequency using a transient solver as given in the attached paper. Kindly suggest the steps for the same. I want to replicate the results of attached paper.https://ieeexplore.ieee.org/document/8410939/

[GioF]

Ronny I won’t be able to check the publication, so I will provide some information based on the provided screenshots.

Based on the attached screenshots, you can do the following. First select the Transient Solver Solution Type. To do so, click on HFSS and select Solution Type.

Create 2 spheres one inside the other and place them inside a bigger box. The outter box region will be used as the vaccum and a radiation boundary should be defined in its outer faces. Select the box right click and do Assign Boundary>Radiation. Assign the inner sphere as PEC and the outer sphere with an isotropic dielectric material. After that you should assign a plane wave excitation by right clicking on Excitations>Incident Wave>Plane wave. Define the wave coordinates and direction and in the Transient Tab of the Incident Wave, select Active.

The issue with the attached screenshots is that a frequency sweep of 2.9-6 GHz with a time step of 0.001 GHz is mentioned. Since, transient solver is a time domain solver a frequency sweep is not defined. In the input signal Tab you can define the Min and Max Frequencies as well as the number of extracted frequencies. You can try adding a solution setup by right clicking on Analysis>Add Solution Setup.Set the Solution Setup options as needed. In the Radiated Fields Tab enable the Save frequency domain radiated fields if you want to plot the CrossSection results.

Last, right click on the Radiation and click on Insert Far Field Setup>Infinite Sphere. Simulate the model and plot the results.