Modeling a WR-90 waveguide with one end embedded in a infinite PEC ground
Hello everyone,
I am a new comer of Altair community.
Recently I am trying to learn FEKO of Altair.
I started with a very simple example, modelling a commonly used antenna radiator, which is a WR-90 waveguide (22.86mm*10.16mm) with one end embedded in a infinite PEC ground to radiate energy into half free space. When I complete the model and try to find its far field 3D pattern with the fundamental TE10 mode as excitation, a error box appears, which says
"The following message from the master process (MYID= 0):
ERROR 270: A triangle may not be located in the ground"
I have attached with this question the .cfs file of the model, could anyone help me to to find out the mistakes?
Thank you very much!
Best Answer
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Unfortunately this type of aperture in an infinite plane is not supported.
(Note that Feko does allow an aperture or hole inside of a an infinite ground plane in for example aperture coupled patch antenna / microstrip applications where the "Plane/ground" type is "planar multilayer substrate", but connecting triangles to this aperture is also not supported)
It is also not supported to use a different axis / change the orientation of the infinite planes.
The alternative is to just define a very large finite plane and solve the model with MLFMM. The finite plane can have any orientation.
The below used a an ellipse of radius 30*lam.
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Answers
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Hi Hongyu Liang
Welcome!
Please attach the cfx file.
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mel_21333 said:
Hi Hongyu Liang
Welcome!
Please attach the cfx file.
Hi, mel,
Nice to receive your reply!
The .cfx file is attached below, I look forward to your answers!
Many thanks for your kind help!
HONGYU LIANG
BTW, in addition to my PEC ground question above, I still have another question related to the coordinate system erected in FEKO modelling, please see below, I also hope to get your help or suggestion!
In the model mentioned above, while I am defining the infinite PEC ground plane, the default setting is to place the plane at z=0 (i.e., the x-o-y plane), in another word, the normal to the PEC ground plane is along the z-axis. However, what I intend to investigate most is the situation in which the PEC ground plane is placed at x=0 (i.e., the y-o-z plane) which comprises the open end of WR-90 waveguide (i.e., the radiator), thus the normal to this plane is along the x-axis.
Such a new definition of global Cartesian coordinate system, especially the new definition of z-axis direction, will inevitably affect the definitions of many variables in associated spherical coordinate system, not only the values and ranges of angle theta and angle phi, but also the directions of unit vectors theta and phi. Thus the far field calculations may exhibit different results, especially for polarimetric (dual-polarization) applications.
So, do you know how to solve this problem? Either by placing the PEC ground plane at x=0 in CADFEKO modelling process, or, by still placing the PEC ground plane at z=0 in modelling first, then finding desired dual-polarization results in the frame of new global Cartesian coordinate system in Run/Solver calculation process?
Many thanks for any answer or suggestion!
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HONGYU LIANG said:
Hi, mel,
Nice to receive your reply!
The .cfx file is attached below, I look forward to your answers!
Many thanks for your kind help!
HONGYU LIANG
BTW, in addition to my PEC ground question above, I still have another question related to the coordinate system erected in FEKO modelling, please see below, I also hope to get your help or suggestion!
In the model mentioned above, while I am defining the infinite PEC ground plane, the default setting is to place the plane at z=0 (i.e., the x-o-y plane), in another word, the normal to the PEC ground plane is along the z-axis. However, what I intend to investigate most is the situation in which the PEC ground plane is placed at x=0 (i.e., the y-o-z plane) which comprises the open end of WR-90 waveguide (i.e., the radiator), thus the normal to this plane is along the x-axis.
Such a new definition of global Cartesian coordinate system, especially the new definition of z-axis direction, will inevitably affect the definitions of many variables in associated spherical coordinate system, not only the values and ranges of angle theta and angle phi, but also the directions of unit vectors theta and phi. Thus the far field calculations may exhibit different results, especially for polarimetric (dual-polarization) applications.
So, do you know how to solve this problem? Either by placing the PEC ground plane at x=0 in CADFEKO modelling process, or, by still placing the PEC ground plane at z=0 in modelling first, then finding desired dual-polarization results in the frame of new global Cartesian coordinate system in Run/Solver calculation process?
Many thanks for any answer or suggestion!
This is the cfs file.
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mel_21333 said:
This is the cfs file.
Hi, mel,
Thank you for your prompt reply!
But I could not see the downloading link for the .cfs file you mentioned.
Attached is the screenshot, only the .cfs files I myself uploaded are displayed.
I do not know what is the problem.
Or, could you send the .cfs file you mentioned to my email box at Hyliang69@outlook.com?
Many thanks for your help!
HONGYU LIANG
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I meant to say that you, again, attached only the cfs file.
Please attach your own cfx file.
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mel_21333 said:
This is the cfs file.
Hi, mel,
Please forgive my carelessness!
I know what the problem is . I should upload the .cfx model file rather than .cfs.
Attached is the .cfx file you mentioned.
Sorry again and hope to get your help!
HONGYU LIANG
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Unfortunately this type of aperture in an infinite plane is not supported.
(Note that Feko does allow an aperture or hole inside of a an infinite ground plane in for example aperture coupled patch antenna / microstrip applications where the "Plane/ground" type is "planar multilayer substrate", but connecting triangles to this aperture is also not supported)
It is also not supported to use a different axis / change the orientation of the infinite planes.
The alternative is to just define a very large finite plane and solve the model with MLFMM. The finite plane can have any orientation.
The below used a an ellipse of radius 30*lam.
1 -
mel_21333 said:
Unfortunately this type of aperture in an infinite plane is not supported.
(Note that Feko does allow an aperture or hole inside of a an infinite ground plane in for example aperture coupled patch antenna / microstrip applications where the "Plane/ground" type is "planar multilayer substrate", but connecting triangles to this aperture is also not supported)
It is also not supported to use a different axis / change the orientation of the infinite planes.
The alternative is to just define a very large finite plane and solve the model with MLFMM. The finite plane can have any orientation.
The below used a an ellipse of radius 30*lam.
Hi, mel,
I am glad to receive your prompt reply, although a bit disappointed to know that this kind of models is not supported by FEKO.
The aperture of open-ended waveguide (or slotted waveguide) embedded in an infinite PEC plane is a typical problem which have been extensively investigated and solved by the aid of classical electromagnetic theory and numerical methods (especially the planar Green’s function/MoM) in literature.
Your advice to define a very large finite plane is much more practical, and I believe the results will be much alike as those for an infinite PEC plane, the biggest difference lies in that there exists radiation in whole space due to diffraction rather than in only half space.
Defining an infinite PEC plane with arbitrary orientation other than within z=0 plane may also find practical values (for not only aperture problems, but also microstrip or other type of radiating elements), especially for polarimetric (dual-polarization) applications. In essence, this is only a problem of coordinate system transformation, I believe it is not difficult to solve.
I wish the future version of FEKO may have further improvements to solve these problems.
Anyway, thank you very much for your quick response and constructive advices!
Regards,
HONGYU LIANG
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Hi Hongyu
I have done further modelling and it seems I was mistaken about some details, apologies for that.
I mentioned that Feko supports aperture triangles (hole in a ground plane) with the planar multilayer substrate. A waveguide port with this option is not supported, however, a wire with voltage source can be used instead. And the waveguide port sides can connect to the aperture triangles. See below.
And the results compare very well with the finite ground plane version:
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mel_21333 said:
Hi Hongyu
I have done further modelling and it seems I was mistaken about some details, apologies for that.
I mentioned that Feko supports aperture triangles (hole in a ground plane) with the planar multilayer substrate. A waveguide port with this option is not supported, however, a wire with voltage source can be used instead. And the waveguide port sides can connect to the aperture triangles. See below.
And the results compare very well with the finite ground plane version:
Hi, mel,
It is very kind of you for doing further modelling.
I have noticed the configuration option of "planar multilayer substrate", which are widely used in microstrip patch analysis.
I do not know more detail about your model. What most important is to cut a hole (aperture) in the infinite PEC ground, and perhaps corresponding boolean operation should be subtarction.
With my understanding, the key problem is whether the infinite PEC ground you defined (layer 0) is an entity. Most models I have looked through are cutting a hole in a finite PEC plane. I do not remember the cases for a hole cut in an infinite PEC plane.
Regards,
Hongyu Liang
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It is an infinite PEC ground, and a rectangle is drawn on the plane, but changed to have the aperture property.
You can view "Example A.10 Aperture Coupled Patch Antenna" in the Altair_Feko_Example_Guide.pdf in the help folder of your Feko installation for detailed instructions.
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mel_21333 said:
Hi Hongyu
I have done further modelling and it seems I was mistaken about some details, apologies for that.
I mentioned that Feko supports aperture triangles (hole in a ground plane) with the planar multilayer substrate. A waveguide port with this option is not supported, however, a wire with voltage source can be used instead. And the waveguide port sides can connect to the aperture triangles. See below.
And the results compare very well with the finite ground plane version:
Hi, mel
Thank you very much for your help and suggestions! Finally, I did succeed to model and solve the radiation of open-ended waveguide embedded in infinite PEC ground (within x-o-y plane) with an excitation of wire voltage, which was modelled as a hole/aperture and solved with multilayer Green’s function. Simulated far field results are very similar to those of yours. Although there is a warning code 1993 concerning directivity in calculation, it does give results. Anyway, I think perhaps there are still some problems encountered concerning both the modelling and the results.
1.In the reply above you mentioned that “The finite plane can have any orientation”. But when I tried to create a rectangle with finite size within y-o-z plane, the default setting is still placing the surface parallel to x-o-y plane. I finally draw the rectangle within y-o-z plane by creating a cuboid first and then delete other unused five faces. But this is a little complex and no use for drawing an ellipse in y-o-z plane. How could you realize this goal? Did you rely on workplane?
2.Although a pin probe is widely used to excite the TE10 mode in waveguide, the results simulated for TE10 excitation will be surely somewhat different from those for a probe excitation, especially for reflection coefficient and higher order modes. The results for multilayer Green’s function may also probably different from those for planar Green’s function. Perhaps other software, e.g., HFSS, may solve such problems?
3.The 3D pattern result itself also seem a little strange, especially for the field near the ground, which should tend to be zero. A paper published before, “Open-Ended Waveguide Radiation Characteristics – Full-Wave Simulation versus Analytical Solutions”, gives far field results simulated with FEKO and HFSS respectively for different size of flange connected to one end of a WR-90 waveguide and may be taken as a reference for comparison. Unfortunately, the result for infinite flange (like infinite PEC ground) was calculated with HFSS, not FEKO. It seems FEKO does indeed have difficulty in solving problems involving the aperture in infinite PEC ground.
I may put new results here if there is further progress.
Thank you again for your kind help!
Regards,
Hongyu Liang
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HONGYU LIANG said:
Hi, mel
Thank you very much for your help and suggestions! Finally, I did succeed to model and solve the radiation of open-ended waveguide embedded in infinite PEC ground (within x-o-y plane) with an excitation of wire voltage, which was modelled as a hole/aperture and solved with multilayer Green’s function. Simulated far field results are very similar to those of yours. Although there is a warning code 1993 concerning directivity in calculation, it does give results. Anyway, I think perhaps there are still some problems encountered concerning both the modelling and the results.
1.In the reply above you mentioned that “The finite plane can have any orientation”. But when I tried to create a rectangle with finite size within y-o-z plane, the default setting is still placing the surface parallel to x-o-y plane. I finally draw the rectangle within y-o-z plane by creating a cuboid first and then delete other unused five faces. But this is a little complex and no use for drawing an ellipse in y-o-z plane. How could you realize this goal? Did you rely on workplane?
2.Although a pin probe is widely used to excite the TE10 mode in waveguide, the results simulated for TE10 excitation will be surely somewhat different from those for a probe excitation, especially for reflection coefficient and higher order modes. The results for multilayer Green’s function may also probably different from those for planar Green’s function. Perhaps other software, e.g., HFSS, may solve such problems?
3.The 3D pattern result itself also seem a little strange, especially for the field near the ground, which should tend to be zero. A paper published before, “Open-Ended Waveguide Radiation Characteristics – Full-Wave Simulation versus Analytical Solutions”, gives far field results simulated with FEKO and HFSS respectively for different size of flange connected to one end of a WR-90 waveguide and may be taken as a reference for comparison. Unfortunately, the result for infinite flange (like infinite PEC ground) was calculated with HFSS, not FEKO. It seems FEKO does indeed have difficulty in solving problems involving the aperture in infinite PEC ground.
I may put new results here if there is further progress.
Thank you again for your kind help!
Regards,
Hongyu Liang
1. You can use the workplane, yes. You can create a new default workplane and all primitives will then use this new workplane. Or you can use the Workplane tab of the Rectangle primitive and change it there. In the Altair_Feko_Example_Guide.pdf, just search for "workplane" for examples of this.
2. I am unable to comment on other software.
3. The field does tend to zero for the infinite plane:
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