Cannot reproduce retroflection feature with current antenna design

[Galaxywalk]

I use Ansys Electronic Desktop 2022.1 to simulate a 24 GHz Van Atta array, but I cannot achieve the correct retroreflection feature.

My setup is as follows:

1. Set an open region (24 GHz) as the boundary.

2. Set a plane wave as excitation. The detailed parameters are: hfss.odesign.GetModule("BoundarySetup").AssignPlaneWave( [ "NAME:IncPWave1", "IsCartesian:=", False, "PhiStart:=", "0deg", "PhiStop:=", "0deg", "PhiPoints:=", 1, "ThetaStart:=", "10deg", "ThetaStop:=", "50deg", "ThetaPoints:=", 21, "EoPhi:=", "1", "EoTheta:=", "0", "OriginX:=", "0mm", "OriginY:=", "0mm", "OriginZ:=", "0mm", "IsPropagating:=", True, "IsEvanescent:=", False, "IsEllipticallyPolarized:=", False ])

3. Set the analysis with the basic 24 GHz settings.

4. Run the simulation and draw the far-field report - radiation pattern with the parameters: Geometry-Elevation, Trace-rE-rETotal-dBm, Families-Phi-0deg, Families-IWaveTheta-10, 20, 30, 40, 50 degrees. My results are:

Taking the 30-degree incident wave as an example, there is a strong mirror reflection wave (at -30 degrees) and a strong transmitted wave (at -150 degrees), but no obvious response at the incident angle of 30 degrees.

Are my methods of setup or result analysis incorrect?

[moonkyul1]

Hello, thank you for your question, and I apologize for the late reply. There was a trouble in finding your question.

The main difference between the simulated and measured retro-reflectivity stems from the reflection on the substrate. This mainly generates the specular reflection signal, but some scattered signals can distort the overall trend of the retro-reflectivity.

You can check the effect of the substrate on the retro-reflectivity, by simulating various sizes of the substrate. (I suggest the use of the monostatic RCS plot, which clearly shows the retro-reflectivity of the tag).

On the other hand, Hawkeye effectively disentangles the reflection on the tag circuit from the clutter (reflection on the substrate) by utilizing HD-FMCW, achieving high retro-reflectivity regardless of the reflection on the substrate.

If you have any other questions, please email me (moonkyul1@kaist.ac.kr).

Thank you, Hankyeol Moon

[Galaxywalk]

Thanks for your response! I still have a couple of questions about doing the monostatic RCS simulation right:

1. For figuring out if the incident wave's angle gives the strongest reflection, should I be looking at the bistatic plot instead? You mentioned the strongest reflection might not come from the incident angle because of how the substrate scatters it.
2. Could you give me more details on how to set up the simulation and post-process for Figure 4 in your paper? I'm not sure how to get started on plotting the monostatic RCS correctly.

I'd really appreciate your help with these!

[moonkyul1]

Hello,

1. Yes, you can check the bistatic plot or radiation pattern (as you did before), to see how much power is reflected somewhere. (As the substrate takes a large portion of Hawkeye tag, I guess the strongest reflection would be the mirror reflection, in HFSS simulation)

2. The retro-reflectivity in Figure 4 is measured by Hawkeye system in real-world (not simulation). For monostatic RCS, it is just a plot, which shows how much power is reflected on the incident angle (as you checked in the radiation plot). I think you can just plot it, as your setting seems almost correct (but don't forget to check the polarization direction when you utilize incident wave excitation).

If you have any other questions, please email me.

Thank you, Hankyeol Moon