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port conditions for single terminal excitation in antennas

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Hi ,

Im Glenston and I have been working on the RF module since a fortnight .
I wanted to excite my antenna using a single terminal .
I tried it with lumped ports it gives an error.
Tried it with ports it also gives an error.

Thanks a lot in advance.
Any kind of help will be greatly appreciated.

Regards
Glenston

21 Replies Last Post 2011年11月1日 GMT-4 15:41

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Posted: 1 decade ago 2011年8月29日 GMT-4 04:36
Hi Glenston,

a uniform lumped port is a good choice for a cable connection. You must make sure that the conductors you want to excite by the port are perfect electrical conductors or you apply an impedance boundary condition.

Cheers
Edgar
Hi Glenston, a uniform lumped port is a good choice for a cable connection. You must make sure that the conductors you want to excite by the port are perfect electrical conductors or you apply an impedance boundary condition. Cheers Edgar

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Posted: 1 decade ago 2011年8月29日 GMT-4 08:08

Hi Glenston,

a uniform lumped port is a good choice for a cable connection. You must make sure that the conductors you want to excite by the port are perfect electrical conductors or you apply an impedance boundary condition.

Cheers
Edgar


Hi Edgar,

I just have one conductor , to which I want to apply the excitation.
The rod is off length 1mm.

Ideally any port has 2 terminals ,ground and the other terminal where the excitation is given(voltage/current).
But since the length of the rod is of very small magnitude (1mm) it takes the ground from the coaxial setup .
This definitely works in CST with excellent results.

I'm attaching the model that I have created with this post.
Please have a look at it and let me know if you have done something related to this.

Regards
Glenston
[QUOTE] Hi Glenston, a uniform lumped port is a good choice for a cable connection. You must make sure that the conductors you want to excite by the port are perfect electrical conductors or you apply an impedance boundary condition. Cheers Edgar [/QUOTE] Hi Edgar, I just have one conductor , to which I want to apply the excitation. The rod is off length 1mm. Ideally any port has 2 terminals ,ground and the other terminal where the excitation is given(voltage/current). But since the length of the rod is of very small magnitude (1mm) it takes the ground from the coaxial setup . This definitely works in CST with excellent results. I'm attaching the model that I have created with this post. Please have a look at it and let me know if you have done something related to this. Regards Glenston


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Posted: 1 decade ago 2011年8月29日 GMT-4 08:45
Glenston,

I suggest we keep it on this thread now.

I checked your model and I think the port setup is entirely wrong. I don't see what the function of the cylinder in the center is. However it is not connected to the spiral or anything. It is just a short circuit.

If you want to excite the spiral you must define a port that connects the two arms of the spiral. You could do that by defining a small rectangle on an xz-workplane that connects to the inner ends of the spiral arms and then make it a uniform port.

If you want to include a coaxial feed, you will need to explicitely include it into the model, define the conductors that connect the coaxial line to the spiral arms and set up a coaxial port across the other end of the cable.

I don't know what CST is. Probably COMSOL has a different way of defining ports. You always need two terminals, the current going into your structure must come out somewhere.

And you will probably need to assign PEC or impedance boundary conditions to the conductors that are connected to the port.

You can have a look into the RF coil tutorial model in the model library that is part of COMSOL. It shows a port definition which is more or less exactly what you need.

Cheers
Edgar
Glenston, I suggest we keep it on this thread now. I checked your model and I think the port setup is entirely wrong. I don't see what the function of the cylinder in the center is. However it is not connected to the spiral or anything. It is just a short circuit. If you want to excite the spiral you must define a port that connects the two arms of the spiral. You could do that by defining a small rectangle on an xz-workplane that connects to the inner ends of the spiral arms and then make it a uniform port. If you want to include a coaxial feed, you will need to explicitely include it into the model, define the conductors that connect the coaxial line to the spiral arms and set up a coaxial port across the other end of the cable. I don't know what CST is. Probably COMSOL has a different way of defining ports. You always need two terminals, the current going into your structure must come out somewhere. And you will probably need to assign PEC or impedance boundary conditions to the conductors that are connected to the port. You can have a look into the RF coil tutorial model in the model library that is part of COMSOL. It shows a port definition which is more or less exactly what you need. Cheers Edgar

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Posted: 1 decade ago 2011年8月30日 GMT-4 03:57

Glenston,

I suggest we keep it on this thread now.

I checked your model and I think the port setup is entirely wrong. I don't see what the function of the cylinder in the center is. However it is not connected to the spiral or anything. It is just a short circuit.

If you want to excite the spiral you must define a port that connects the two arms of the spiral. You could do that by defining a small rectangle on an xz-workplane that connects to the inner ends of the spiral arms and then make it a uniform port.

If you want to include a coaxial feed, you will need to explicitely include it into the model, define the conductors that connect the coaxial line to the spiral arms and set up a coaxial port across the other end of the cable.

I don't know what CST is. Probably COMSOL has a different way of defining ports. You always need two terminals, the current going into your structure must come out somewhere.

And you will probably need to assign PEC or impedance boundary conditions to the conductors that are connected to the port.

You can have a look into the RF coil tutorial model in the model library that is part of COMSOL. It shows a port definition which is more or less exactly what you need.

Cheers
Edgar


Hi Edgar,

Thanks a lot for your reply.
It does not need contact because its being remotely excited with em waves from the feed.
The distance between the feed and the spirals is 750 micrometer and the wavelength for
which i'm executing the model is from 0.3m-0.012m. Thus there will be a current distribution
that is generated in the spirals due to the em waves given out from the top of the cylinder.

Started learning the port conditions to understand how you set it up in the yagi uda antenna.
In your yagu uda antenna model why have you incorporated points in your geometry?

Thanks a lot for your time and effort!

Regards
Glenston
[QUOTE] Glenston, I suggest we keep it on this thread now. I checked your model and I think the port setup is entirely wrong. I don't see what the function of the cylinder in the center is. However it is not connected to the spiral or anything. It is just a short circuit. If you want to excite the spiral you must define a port that connects the two arms of the spiral. You could do that by defining a small rectangle on an xz-workplane that connects to the inner ends of the spiral arms and then make it a uniform port. If you want to include a coaxial feed, you will need to explicitely include it into the model, define the conductors that connect the coaxial line to the spiral arms and set up a coaxial port across the other end of the cable. I don't know what CST is. Probably COMSOL has a different way of defining ports. You always need two terminals, the current going into your structure must come out somewhere. And you will probably need to assign PEC or impedance boundary conditions to the conductors that are connected to the port. You can have a look into the RF coil tutorial model in the model library that is part of COMSOL. It shows a port definition which is more or less exactly what you need. Cheers Edgar [/QUOTE] Hi Edgar, Thanks a lot for your reply. It does not need contact because its being remotely excited with em waves from the feed. The distance between the feed and the spirals is 750 micrometer and the wavelength for which i'm executing the model is from 0.3m-0.012m. Thus there will be a current distribution that is generated in the spirals due to the em waves given out from the top of the cylinder. Started learning the port conditions to understand how you set it up in the yagi uda antenna. In your yagu uda antenna model why have you incorporated points in your geometry? Thanks a lot for your time and effort! Regards Glenston

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Posted: 1 decade ago 2011年8月30日 GMT-4 05:04
Glenston,

well, this yagi-uda antenna was my first test case for RF and I had assumed I needed the points to plot S-parameters. This is not the case but I didn't remove them because removing or adding geometry elements always messes the boundary definitions up.

Good luck with your spiral!
Edgar
Glenston, well, this yagi-uda antenna was my first test case for RF and I had assumed I needed the points to plot S-parameters. This is not the case but I didn't remove them because removing or adding geometry elements always messes the boundary definitions up. Good luck with your spiral! Edgar

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Posted: 1 decade ago 2011年9月14日 GMT-4 02:26

Glenston,

well, this yagi-uda antenna was my first test case for RF and I had assumed I needed the points to plot S-parameters. This is not the case but I didn't remove them because removing or adding geometry elements always messes the boundary definitions up.

Good luck with your spiral!
Edgar


Hi Edgar,

I'm back again. Ive created this model that is very close to what you had advised.
I've altered it to get a geometry that you had suggested me to use.
I'm still not getting suitable results.

The dielectric used is Quartz and the diameters of the inner and outer conductor is
chosen such that the impedance offered by the feed is 50 ohms. My S11 in dB is showing
in terms of 0.001 magnitude which implies that there is no transfer of power at the port.

I've attached the model file in this post.
It looks fine to me .
Please let me know if you can figure out something from it.

Thanks a lot for your time and effort!!

Regards
Glenston

[QUOTE] Glenston, well, this yagi-uda antenna was my first test case for RF and I had assumed I needed the points to plot S-parameters. This is not the case but I didn't remove them because removing or adding geometry elements always messes the boundary definitions up. Good luck with your spiral! Edgar [/QUOTE] Hi Edgar, I'm back again. Ive created this model that is very close to what you had advised. I've altered it to get a geometry that you had suggested me to use. I'm still not getting suitable results. The dielectric used is Quartz and the diameters of the inner and outer conductor is chosen such that the impedance offered by the feed is 50 ohms. My S11 in dB is showing in terms of 0.001 magnitude which implies that there is no transfer of power at the port. I've attached the model file in this post. It looks fine to me . Please let me know if you can figure out something from it. Thanks a lot for your time and effort!! Regards Glenston


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Posted: 1 decade ago 2011年9月14日 GMT-4 03:55
Hi Glenston,

Your current setup creates a short circuit at the end of the feedline. I think you must connect one branch of the spiral to the inner conductor of your feedline and the other branch to the outer conductor.
This is still not optimal because you are feeding from an unbalanced coaxial feed into a symmetric structure but it will certainly result in better S11. You will probably see some common mode on the feed and some mismatch because the spiral's impedance is probably not 50 Ohms in most parts of the spectrum.

Cheers
Edgar
Hi Glenston, Your current setup creates a short circuit at the end of the feedline. I think you must connect one branch of the spiral to the inner conductor of your feedline and the other branch to the outer conductor. This is still not optimal because you are feeding from an unbalanced coaxial feed into a symmetric structure but it will certainly result in better S11. You will probably see some common mode on the feed and some mismatch because the spiral's impedance is probably not 50 Ohms in most parts of the spectrum. Cheers Edgar

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Posted: 1 decade ago 2011年9月14日 GMT-4 10:38

Hi Glenston,

Your current setup creates a short circuit at the end of the feedline. I think you must connect one branch of the spiral to the inner conductor of your feedline and the other branch to the outer conductor.
This is still not optimal because you are feeding from an unbalanced coaxial feed into a symmetric structure but it will certainly result in better S11. You will probably see some common mode on the feed and some mismatch because the spiral's impedance is probably not 50 Ohms in most parts of the spectrum.

Cheers
Edgar


Hi Edgar,

Thanks a lot for your reply.
I tried another very simple setup by replicating what was done in the RF Coil model by using a uniform port.
The VSWR values are still coming very high.

It would be great if you could just have a look at it and let me know what has gone wrong.
Is it the meshing?
Ive attached the model in this post.

Thanks a lot for your time and effort.


Regards
Glenston
[QUOTE] Hi Glenston, Your current setup creates a short circuit at the end of the feedline. I think you must connect one branch of the spiral to the inner conductor of your feedline and the other branch to the outer conductor. This is still not optimal because you are feeding from an unbalanced coaxial feed into a symmetric structure but it will certainly result in better S11. You will probably see some common mode on the feed and some mismatch because the spiral's impedance is probably not 50 Ohms in most parts of the spectrum. Cheers Edgar [/QUOTE] Hi Edgar, Thanks a lot for your reply. I tried another very simple setup by replicating what was done in the RF Coil model by using a uniform port. The VSWR values are still coming very high. It would be great if you could just have a look at it and let me know what has gone wrong. Is it the meshing? Ive attached the model in this post. Thanks a lot for your time and effort. Regards Glenston


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Posted: 1 decade ago 2011年9月14日 GMT-4 11:34
Glenston,

I noticed a small gap between the inner end of one of the spiral branches and the rectangle connecting it to the port.

You must zoom into the geometry to see it.

Cheers
Edgar
Glenston, I noticed a small gap between the inner end of one of the spiral branches and the rectangle connecting it to the port. You must zoom into the geometry to see it. Cheers Edgar

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Posted: 1 decade ago 2011年9月14日 GMT-4 16:52


Hi Glenston,

Your current setup creates a short circuit at the end of the feedline. I think you must connect one branch of the spiral to the inner conductor of your feedline and the other branch to the outer conductor.
This is still not optimal because you are feeding from an unbalanced coaxial feed into a symmetric structure but it will certainly result in better S11. You will probably see some common mode on the feed and some mismatch because the spiral's impedance is probably not 50 Ohms in most parts of the spectrum.

Cheers
Edgar


Hi Edgar,

Thanks a lot for your reply.
I tried another very simple setup by replicating what was done in the RF Coil model by using a uniform port.
The VSWR values are still coming very high.

It would be great if you could just have a look at it and let me know what has gone wrong.
Is it the meshing?
Ive attached the model in this post.

Thanks a lot for your time and effort.


Regards
Glenston


I have been watching this thread just because I am curious about the end result. With the spiral antenna2 file you posted, the free tet mesh was quite big. I was getting close to 1million elements. I am not very good at doing them but this example gave me a chance to try and use a swept mesh. If what I did works, the amount of unknowns have been reduced a lot. If not, no harm no foul. Maybe you can check this out and see if what I did is ok. If it works, great. You can also go in a change this so that you get more elements. Given that your structure is so thin at 10um, a swept mesh is better than just a free tet.

I do see the little geometry error on the mesh where Edgar was hinting at in his last post. It looks like you geometry is ok but it is odd that you are getting a discrepancy here. Not sure how to fix it if it really is a problem.

I did this is ver4.2. I see that you did it in 4.1. That might be a problem. I can try and fix it tomorrow when I get a chance. Sorry.
[QUOTE] [QUOTE] Hi Glenston, Your current setup creates a short circuit at the end of the feedline. I think you must connect one branch of the spiral to the inner conductor of your feedline and the other branch to the outer conductor. This is still not optimal because you are feeding from an unbalanced coaxial feed into a symmetric structure but it will certainly result in better S11. You will probably see some common mode on the feed and some mismatch because the spiral's impedance is probably not 50 Ohms in most parts of the spectrum. Cheers Edgar [/QUOTE] Hi Edgar, Thanks a lot for your reply. I tried another very simple setup by replicating what was done in the RF Coil model by using a uniform port. The VSWR values are still coming very high. It would be great if you could just have a look at it and let me know what has gone wrong. Is it the meshing? Ive attached the model in this post. Thanks a lot for your time and effort. Regards Glenston [/QUOTE] I have been watching this thread just because I am curious about the end result. With the spiral antenna2 file you posted, the free tet mesh was quite big. I was getting close to 1million elements. I am not very good at doing them but this example gave me a chance to try and use a swept mesh. If what I did works, the amount of unknowns have been reduced a lot. If not, no harm no foul. Maybe you can check this out and see if what I did is ok. If it works, great. You can also go in a change this so that you get more elements. Given that your structure is so thin at 10um, a swept mesh is better than just a free tet. I do see the little geometry error on the mesh where Edgar was hinting at in his last post. It looks like you geometry is ok but it is odd that you are getting a discrepancy here. Not sure how to fix it if it really is a problem. I did this is ver4.2. I see that you did it in 4.1. That might be a problem. I can try and fix it tomorrow when I get a chance. Sorry.


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Posted: 1 decade ago 2011年9月15日 GMT-4 05:39

Glenston,

I noticed a small gap between the inner end of one of the spiral branches and the rectangle connecting it to the port.

You must zoom into the geometry to see it.

Cheers
Edgar

Hi,

Thanks a lot !!!
Edgar.


Cheers
Glenston
[QUOTE] Glenston, I noticed a small gap between the inner end of one of the spiral branches and the rectangle connecting it to the port. You must zoom into the geometry to see it. Cheers Edgar [/QUOTE] Hi, Thanks a lot !!! Edgar. Cheers Glenston

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Posted: 1 decade ago 2011年9月15日 GMT-4 06:54

Glenston,

I noticed a small gap between the inner end of one of the spiral branches and the rectangle connecting it to the port.

You must zoom into the geometry to see it.

Cheers
Edgar


Hey Edgar,

I deleted that gap. The mistake was that I approximated the value of pi.
I rectified that error , but VSWR came really high.

I'm stuck at this moment .
Will be waiting for your reply.

Regards
Glenston
[QUOTE] Glenston, I noticed a small gap between the inner end of one of the spiral branches and the rectangle connecting it to the port. You must zoom into the geometry to see it. Cheers Edgar [/QUOTE] Hey Edgar, I deleted that gap. The mistake was that I approximated the value of pi. I rectified that error , but VSWR came really high. I'm stuck at this moment . Will be waiting for your reply. Regards Glenston


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Posted: 1 decade ago 2011年9月15日 GMT-4 07:07



Hi Glenston,

Your current setup creates a short circuit at the end of the feedline. I think you must connect one branch of the spiral to the inner conductor of your feedline and the other branch to the outer conductor.
This is still not optimal because you are feeding from an unbalanced coaxial feed into a symmetric structure but it will certainly result in better S11. You will probably see some common mode on the feed and some mismatch because the spiral's impedance is probably not 50 Ohms in most parts of the spectrum.

Cheers
Edgar


Hi Edgar,

Thanks a lot for your reply.
I tried another very simple setup by replicating what was done in the RF Coil model by using a uniform port.
The VSWR values are still coming very high.

It would be great if you could just have a look at it and let me know what has gone wrong.
Is it the meshing?
Ive attached the model in this post.

Thanks a lot for your time and effort.


Regards
Glenston


I have been watching this thread just because I am curious about the end result. With the spiral antenna2 file you posted, the free tet mesh was quite big. I was getting close to 1million elements. I am not very good at doing them but this example gave me a chance to try and use a swept mesh. If what I did works, the amount of unknowns have been reduced a lot. If not, no harm no foul. Maybe you can check this out and see if what I did is ok. If it works, great. You can also go in a change this so that you get more elements. Given that your structure is so thin at 10um, a swept mesh is better than just a free tet.

I do see the little geometry error on the mesh where Edgar was hinting at in his last post. It looks like you geometry is ok but it is odd that you are getting a discrepancy here. Not sure how to fix it if it really is a problem.

I did this is ver4.2. I see that you did it in 4.1. That might be a problem. I can try and fix it tomorrow when I get a chance. Sorry.


Hi Brown,

Thanks a lot for replying. I did as you told me but its giving me an error in 4.1.
I opened it in 4.2 and tried replicating exactly what was done in the 4.2 model.

Let me know if you can debug the error that i'm getting!!!

I'l be attaching the model with the error node.
Regards
Glenston
[QUOTE] [QUOTE] [QUOTE] Hi Glenston, Your current setup creates a short circuit at the end of the feedline. I think you must connect one branch of the spiral to the inner conductor of your feedline and the other branch to the outer conductor. This is still not optimal because you are feeding from an unbalanced coaxial feed into a symmetric structure but it will certainly result in better S11. You will probably see some common mode on the feed and some mismatch because the spiral's impedance is probably not 50 Ohms in most parts of the spectrum. Cheers Edgar [/QUOTE] Hi Edgar, Thanks a lot for your reply. I tried another very simple setup by replicating what was done in the RF Coil model by using a uniform port. The VSWR values are still coming very high. It would be great if you could just have a look at it and let me know what has gone wrong. Is it the meshing? Ive attached the model in this post. Thanks a lot for your time and effort. Regards Glenston [/QUOTE] I have been watching this thread just because I am curious about the end result. With the spiral antenna2 file you posted, the free tet mesh was quite big. I was getting close to 1million elements. I am not very good at doing them but this example gave me a chance to try and use a swept mesh. If what I did works, the amount of unknowns have been reduced a lot. If not, no harm no foul. Maybe you can check this out and see if what I did is ok. If it works, great. You can also go in a change this so that you get more elements. Given that your structure is so thin at 10um, a swept mesh is better than just a free tet. I do see the little geometry error on the mesh where Edgar was hinting at in his last post. It looks like you geometry is ok but it is odd that you are getting a discrepancy here. Not sure how to fix it if it really is a problem. I did this is ver4.2. I see that you did it in 4.1. That might be a problem. I can try and fix it tomorrow when I get a chance. Sorry. [/QUOTE] Hi Brown, Thanks a lot for replying. I did as you told me but its giving me an error in 4.1. I opened it in 4.2 and tried replicating exactly what was done in the 4.2 model. Let me know if you can debug the error that i'm getting!!! I'l be attaching the model with the error node. Regards Glenston


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Posted: 1 decade ago 2011年9月15日 GMT-4 08:57
Your ver3 file had a couple errors in it. Please see attached file for the corrections.

You needed to use a free triangular mesh and not a free tet mesh. Also one of the mapped distributions boundaries was incorrect. Not sure why your file differed a bit from what I had post with the ver2 antenna but it looks good now. I did this in ver4.2.

I based the swept mesh using comsol's KB at the following location.

www.comsol.com/support/knowledgebase/120/

dennis
Your ver3 file had a couple errors in it. Please see attached file for the corrections. You needed to use a free triangular mesh and not a free tet mesh. Also one of the mapped distributions boundaries was incorrect. Not sure why your file differed a bit from what I had post with the ver2 antenna but it looks good now. I did this in ver4.2. I based the swept mesh using comsol's KB at the following location. http://www.comsol.com/support/knowledgebase/120/ dennis


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Posted: 1 decade ago 2011年9月16日 GMT-4 04:50

Your ver3 file had a couple errors in it. Please see attached file for the corrections.

You needed to use a free triangular mesh and not a free tet mesh. Also one of the mapped distributions boundaries was incorrect. Not sure why your file differed a bit from what I had post with the ver2 antenna but it looks good now. I did this in ver4.2.

I based the swept mesh using comsol's KB at the following location.

www.comsol.com/support/knowledgebase/120/

dennis


Hi Dennis,

A triangular mesh is only for the boundaries , what about meshing the domains 1 and 2?
Your model is not computing ,its giving errors.

I'm working on it , thought il update you .
Thanks a lto for your help!

Regards
Glenston
[QUOTE] Your ver3 file had a couple errors in it. Please see attached file for the corrections. You needed to use a free triangular mesh and not a free tet mesh. Also one of the mapped distributions boundaries was incorrect. Not sure why your file differed a bit from what I had post with the ver2 antenna but it looks good now. I did this in ver4.2. I based the swept mesh using comsol's KB at the following location. http://www.comsol.com/support/knowledgebase/120/ dennis [/QUOTE] Hi Dennis, A triangular mesh is only for the boundaries , what about meshing the domains 1 and 2? Your model is not computing ,its giving errors. I'm working on it , thought il update you . Thanks a lto for your help! Regards Glenston


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Posted: 1 decade ago 2011年10月31日 GMT-4 14:52

Glenston,

I noticed a small gap between the inner end of one of the spiral branches and the rectangle connecting it to the port.

You must zoom into the geometry to see it.

Cheers
Edgar


Hi Edgar,

I'm back again to haunt you.
I created a very simple model.
A plain coaxial cable setup such that its characteristic impedance is 50 ohm.
2 ports have been assigned with 50 ohm as ref imp.
Now my ideal S11 and S22 should be infinity or very large value.
S12 and S21 should be close to 0.

I don't know if i've missed something here or ive not understood something properly.
I've attached the model below.

Thanks a lot for your time and effort.

Regards
Glenston
[QUOTE] Glenston, I noticed a small gap between the inner end of one of the spiral branches and the rectangle connecting it to the port. You must zoom into the geometry to see it. Cheers Edgar [/QUOTE] Hi Edgar, I'm back again to haunt you. I created a very simple model. A plain coaxial cable setup such that its characteristic impedance is 50 ohm. 2 ports have been assigned with 50 ohm as ref imp. Now my ideal S11 and S22 should be infinity or very large value. S12 and S21 should be close to 0. I don't know if i've missed something here or ive not understood something properly. I've attached the model below. Thanks a lot for your time and effort. Regards Glenston


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Posted: 1 decade ago 2011年10月31日 GMT-4 15:59
First off, you can only have one port on at a time. Just turn off either port 1 or port 2. This also means that you can only calculate S11, S21 OR not S22, S12. Since you have a symmetrical structure, you really don't need to calculate it all. You can turn the othe port on if you want to calculate the other way.

You can simplify your geometry by just using two cylinders upfront and difference out the center one. This way you only need to apply IBC's to all of your gold surfaces. Skin depth is pretty small at your analysis freqs. This will also make your model run faster.

The port faces should be meshed fairly fine. I uploaded my mods and hopefully you can open the file. My version of comsol is 4.2.0.228 and what you uploaded was 4.2.0.150. You could also upgrade it with patches if you are on maintenance.
First off, you can only have one port on at a time. Just turn off either port 1 or port 2. This also means that you can only calculate S11, S21 OR not S22, S12. Since you have a symmetrical structure, you really don't need to calculate it all. You can turn the othe port on if you want to calculate the other way. You can simplify your geometry by just using two cylinders upfront and difference out the center one. This way you only need to apply IBC's to all of your gold surfaces. Skin depth is pretty small at your analysis freqs. This will also make your model run faster. The port faces should be meshed fairly fine. I uploaded my mods and hopefully you can open the file. My version of comsol is 4.2.0.228 and what you uploaded was 4.2.0.150. You could also upgrade it with patches if you are on maintenance.


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Posted: 1 decade ago 2011年10月31日 GMT-4 17:50

First off, you can only have one port on at a time. Just turn off either port 1 or port 2. This also means that you can only calculate S11, S21 OR not S22, S12. Since you have a symmetrical structure, you really don't need to calculate it all. You can turn the othe port on if you want to calculate the other way.

You can simplify your geometry by just using two cylinders upfront and difference out the center one. This way you only need to apply IBC's to all of your gold surfaces. Skin depth is pretty small at your analysis freqs. This will also make your model run faster.

The port faces should be meshed fairly fine. I uploaded my mods and hopefully you can open the file. My version of comsol is 4.2.0.228 and what you uploaded was 4.2.0.150. You could also upgrade it with patches if you are on maintenance.


Hi Dennis,

Thanks a lot for your reply.
It helped me a lot.
Another simple problem that i had was on the model of a coplanar wavequide,
Its a fairly simple structure.
I'm finding it extremely difficult to assign a port to it.

I'm attaching the file in this post.
Please have a look at it and let me know how i can assign a port condition to the model.
thanks a lot for your time and effort.

Regards
Glenston
[QUOTE] First off, you can only have one port on at a time. Just turn off either port 1 or port 2. This also means that you can only calculate S11, S21 OR not S22, S12. Since you have a symmetrical structure, you really don't need to calculate it all. You can turn the othe port on if you want to calculate the other way. You can simplify your geometry by just using two cylinders upfront and difference out the center one. This way you only need to apply IBC's to all of your gold surfaces. Skin depth is pretty small at your analysis freqs. This will also make your model run faster. The port faces should be meshed fairly fine. I uploaded my mods and hopefully you can open the file. My version of comsol is 4.2.0.228 and what you uploaded was 4.2.0.150. You could also upgrade it with patches if you are on maintenance. [/QUOTE] Hi Dennis, Thanks a lot for your reply. It helped me a lot. Another simple problem that i had was on the model of a coplanar wavequide, Its a fairly simple structure. I'm finding it extremely difficult to assign a port to it. I'm attaching the file in this post. Please have a look at it and let me know how i can assign a port condition to the model. thanks a lot for your time and effort. Regards Glenston


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Posted: 1 decade ago 2011年11月1日 GMT-4 11:20
Did you check out this model file on the website? Pretty close to what you want to do.

www.comsol.com/showroom/documentation/model/2192/

Just looking at your file, you will need an airbox around the structure. This is shown in the above file as well. The above is in ver3.5a but it should translate ok to 4.2 (I believe). There is also a step by step pdf file there as well.
Did you check out this model file on the website? Pretty close to what you want to do. http://www.comsol.com/showroom/documentation/model/2192/ Just looking at your file, you will need an airbox around the structure. This is shown in the above file as well. The above is in ver3.5a but it should translate ok to 4.2 (I believe). There is also a step by step pdf file there as well.

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Posted: 1 decade ago 2011年11月1日 GMT-4 13:10

Did you check out this model file on the website? Pretty close to what you want to do.

www.comsol.com/showroom/documentation/model/2192/

Just looking at your file, you will need an airbox around the structure. This is shown in the above file as well. The above is in ver3.5a but it should translate ok to 4.2 (I believe). There is also a step by step pdf file there as well.


Hi Dennis,

Thanks a lot for your reply .
The model looks more or less similar to mine.
A question that i have, what does uniform lumped port represent in real life.

Does it represent a TX line input ?
Does it represent a TEM mode transmission?

Regards
Glenston
[QUOTE] Did you check out this model file on the website? Pretty close to what you want to do. http://www.comsol.com/showroom/documentation/model/2192/ Just looking at your file, you will need an airbox around the structure. This is shown in the above file as well. The above is in ver3.5a but it should translate ok to 4.2 (I believe). There is also a step by step pdf file there as well. [/QUOTE] Hi Dennis, Thanks a lot for your reply . The model looks more or less similar to mine. A question that i have, what does uniform lumped port represent in real life. Does it represent a TX line input ? Does it represent a TEM mode transmission? Regards Glenston

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Posted: 1 decade ago 2011年11月1日 GMT-4 15:41


Did you check out this model file on the website? Pretty close to what you want to do.

www.comsol.com/showroom/documentation/model/2192/

Just looking at your file, you will need an airbox around the structure. This is shown in the above file as well. The above is in ver3.5a but it should translate ok to 4.2 (I believe). There is also a step by step pdf file there as well.


Hi Dennis,

Thanks a lot for your reply .
The model looks more or less similar to mine.
A question that i have, what does uniform lumped port represent in real life.

Does it represent a TX line input ?
Does it represent a TEM mode transmission?

Regards
Glenston


I think what you are getting is just a BC with 1V (or whatever value you pick) applied to the boundary.

The lumped port BC is just a simpler version of the port BC. Check the docs for specifics but I don't really recall if they answer your question the way that you posed it.
[QUOTE] [QUOTE] Did you check out this model file on the website? Pretty close to what you want to do. http://www.comsol.com/showroom/documentation/model/2192/ Just looking at your file, you will need an airbox around the structure. This is shown in the above file as well. The above is in ver3.5a but it should translate ok to 4.2 (I believe). There is also a step by step pdf file there as well. [/QUOTE] Hi Dennis, Thanks a lot for your reply . The model looks more or less similar to mine. A question that i have, what does uniform lumped port represent in real life. Does it represent a TX line input ? Does it represent a TEM mode transmission? Regards Glenston [/QUOTE] I think what you are getting is just a BC with 1V (or whatever value you pick) applied to the boundary. The lumped port BC is just a simpler version of the port BC. Check the docs for specifics but I don't really recall if they answer your question the way that you posed it.

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