Which EM solver to be used to simulate antenna placed inside the car model in CADFEKO?

Sanjali Sharma

hello everyone,

I'm trying to simulate helix antenna with rubber cover, placed inside a car model. Antenna location is at the bottom surface of car and it is having operational frequency of 440 MHz, but when I simulate the overall model, error comes as shown.

Solver used is MoM with HOBF 3.5 order, I also tried with MLFMM but again error comes. I'm using a system having around 200GB space in SSD and 32GB RAM.  I am attaching CADFEKO file for the reference . If anyone can help me find the mistake I'm making and suggest me other ways to simulate it and explain it, that would be helpful.

Also how can we move antenna at specific required location inside the car, procedure for it.

Thank you.

cad model.cfx

Mel

The model contains very fine details inside the antenna compared to the car. The best solver for such cases is FEM for the antenna and MoM or MLFMM for the car.

It may not always be immediately clear whether to use MLFMM, or MoM, or MoM with HOBF. Running the solver at the lowest and highest frequencies should give an indication.

The align tool can be used to place the antenna against the car surface. Using the align tool, set the Source workplane to the center bottom of the antenna. 

The Destination workplane is then the car surface. Use CTRL+SHIFT to grab geometry points of interest.

To use the FEM for the helix, please see the below two videos. These videos demonstrates step-by-step the setup of an antenna with small details, a dielectric resonator antenna, first with the default solver: 

 Then in the 2nd part, this model is converted to FEM:

 

The helix surface is flat, but the car's surface is not flat everywhere. In the below images I made a small platform out of the helix ground plane (copy the edge and use Sweep) which is extended through the car surface. After a Union, delete the protruding part. This will ensure the mesh will connect between the helix and car surface. Of course, in the Align step, I positioned the helix a few mm just above the car surface.

Usually in these cases where there is such a very large ratio between smallest and largest mesh elements it is recommended to use double precision in the solver. In addition, switching the FEM to use first order basis functions is recommended when the FEM elements are very small compared to the wavelength.

I made some (over?) simplifications in the feed of the helix - please see the attached model as a CONCEPT only.

It uses about 6 GByte of memory.

 

align1.png

Community-Pasted-Attachment-1628056334768.png

helix_and_car_FEM_nomesh.cfx