Learning Forum

[mkamrul]

Hi everyone,

I recently designed a horn antenna in HFSS using the Antenna Toolkit. The design specifications and dimensions are for it to operate up to a maximum frequency of 40–45 GHz. However, the simulated S11 response shows that the antenna is working (below -10 dB) up to 80 GHz, which doesn't make sense for my design. The S11 response also appears unusually constant over the entire frequency range.

• I used the radiation boundary for the setup.

I suspect something is wrong with my simulation, but I’m unsure where to start troubleshooting. Could this be due to boundary placement, mesh settings, or something else?

Attached is the S11 plot for reference.

Any suggestions on how to identify and fix the issue would be greatly appreciated!

Thank you in advance!

[mkamrul]

E field Mag at 33 GHz

[vphase]

Please share the simulation file to allow others to examine your structure and offer assistance

[mkamrul]

Hi, I added a Simulation file here: https://drive.google.com/file/d/1kzKYvF4VwWYXGnmBcamks-Ywk9Po0hRr/view?usp=sharing

[vphase]

Hello,

When a waveguide is excited with a frequency exceeding its cutoff frequency, the fundamental mode is initially stimulated. As the frequency increases further, higher-order modes will begin to propagate within the waveguide. In your specific setup, the waveguide is excited at approximately 16 GHz, ensuring the presence of at least the fundamental mode. Higher frequencies will subsequently generate additional modes. Consequently, impedance matching between the excitation port and the waveguide can occur for various modes. This can result in transmission through the antenna. However, concerning antenna performance, the radiation efficiency is unlikely to be optimal beyond the antenna's intended bandwidth.

[mkamrul]

Does this mean that because of the higher-order mode, it is showing a strange S11 over 40GHz? Right? My target is to find out the bandwidth coverage for this one like other antennas. How can I do that? Which parameter can I observe? Or is there any way to filter out the other modes?