This is very easy.  See the attached images.

1. To increase the number of modes, go to "Excitations" and select "Properties" for each of the excited port. In the "Modes" tab, assign the required "Number of Modes". You can set the Mode Polarity or Align the modes using integration lines.

2. After simulation, you can look for the modes in "Port Field Display". It will show the propagating modes and the direction of Electric Fields on the Wave Ports. By the direction of Electric fields, you can understand which mode is propagating. You can even zoom in to the region.

3. From the propagation constant (imaginary part of gamma) vs. frequency, you can view propagation at various frequencies. For this, create a New Report with Gamma (img) vs. Frequency for Each Mode. See the second attached image.  

Hello Kumar,

Check this links :

http://www.emtalk.com/forums/viewtopic.php?t=215

http://www.edaboard.com/thread75166.html

I wish that can help you,

Best regards

Dear Suhas,

In your answer you mentioned like "By the direction of Electric fields, you can understand which mode is propagating", but how and what could be the direction of Electric fields?

And finally what are the directions of integration lines?

Dear Anvesh, Your basic requirement is to find no of modes using HFSS but you did not mention the investigated object. Assuming you are investigating an antenna/resonator etc. Then follow the steps: plot fr vs Zin. (not S11). Identify the peaks on R (real of Zin). No of excited mode = no of peaks within your region of interest. Plot internal E/H field to identify different modes.

2. Assuming you are investigating waveguide. Then excite the waveguide using 20/30 no of modes in simulation. Then HFSS gives field for different modes automatically. To identify frequency (cut-off) for different modes, plot plot propagation constant. Initially, it will be zero up to certain frequency. then it will take non zero positive value. This point is the cut-off frequency

3. Assuming you are simulating electromagnetic object having finite dimensions (antenna/resonator/oscillator etc but not waveguide). first draw your structure without excitation. Then enclose it by metallic cavity. use eigenmode solver. It will give all modes within the electromagnetic object. If you use excitation, it will suppress some modes (basically, these modes are not effectively coupled, hence suppressed)

The Direction of Electric Fields can be seen on the Wave Ports used. The Integration Line is used to set the Direction of Electric Fields. If you swap the ends of the integration line, the direction of the Electric Field also inverts. Let us take the simple example of a Rectangular Waveguide (WR-90; 900mils x 400mils):

The propagation constant vs. frequency is shown upto 100 GHz in the first picture. You can see there are four propagating modes. 

To understand what these modes are, you can look for the direction of Electric Fields on the Wave Ports.

The second attached picture shows the direction of Electric Fields for the first mode. If you understood, this is TE10 mode (see the last attached figure), which is called as the dominant mode (has the lowest cut off frequency of 6.57 GHz).

The third attached picture shows the direction of Electric Fields for the second mode. This is TE20 mode (has a cut off frequency of 13.1 GHz).

The fourth attached picture shows the direction of Electric Fields for the third mode. This is TE01 mode (has a cut off frequency of 14.67 GHz).

The fifth attached picture shows the direction of Electric Fields for the fourth mode. This is TE11 mode (has a cut off frequency of 16.14 GHz).

The direction of the Integration line on the Wave Port is shown in the sixth attached picture, for you to visualize and interconnect the direction of both: Electric Field of modes and Integration line.

Senior Researchers, please correct me if you find any mistakes.

Warm Regards,

Suhas. D.

Thank you very much suhas and sudipta for your wonderful answers.......

can anyone plz tell me how to assign the waveport using HFSS ..?

Please consult the help manual to learn A - Z of HFSS. Wave port is also there.

Thank you so much sir for your help.

Please try to learn 5.3 Section (Example – Probe Feed Patch Antenna), 200 is the page no in PDF.

Hello all,

Thank you for this wonderful comments. They helped me to know how to work with HFSS.

However, I am trying to simulate WR62 for multiple frequencies. There are couples of terminologies I am not familiar with in HFSS. Please is the meaning of number pf passes, and the solution frequency.

Thank you

1. Using the "Eigenmode" Solver, then analyze.

2. Plot the E field or H field in plane. (Using "Draw plane" tool).

3. Change the field source by menu "HFSS -> Fields -> Edit Sources".

Respected Prof. Jin,

In eigenmode solver, we do not have to give excitation. In practice, excitation is there. Due to excitation, some mode will be excited and some will not be excited. If we use analytical theory without any source, then eigenmode is a good option. Otherwise, observing Zin with respect to frequency would be better option (even not, S11) to find the existence of a particular mode for that excitation.

I'm waiting for your valuable response. Finally, we have to know the correct path. Please guide me sir.

Agree with Qi Jin Sir. No. of modes can be found using Eigen Mode Solver and observing real and imaginary values in the Eigen Number.

thank you

It is better to use excitation while using eigenmode solver. The modes which are excited due to that feeding mechanism will be shown only.

Hi all,

can you explain how to deal with degenerate modes in a square waveguide?

Thanks in advance

Dear Sir, What is your actual requirements? Do you want to see the degenerate modes in HFSS or you want to excite it practically???