Simulation of two Small Interacting Antennas

[bob012345]

TL;DR Summary

I would like to simulate two small interacting antenna's with fields and forces in 3D.

I would like to simulate two small interacting antenna's with fields and forces in 3D. They can be simple wire antenna. I am asking if there is a recommendation for software that can reasonably accurately handle that which is free? Thanks.

 

[berkeman]

When you say "small", do you mean electriclly small, as in way less than half a wavelength? And why are you asking about forces -- is this more than an antenna array pattern problem?

 

[bob012345]

When you say "small", do you mean electriclly small, as in way less than half a wavelength? And why are you asking about forces -- is this more than an antenna array pattern problem?

Thanks. I am not primarily interested in antenna's per se I but I mean physically small ~cm length wires with oscillating currents near each other. I am interested in the fields and forces especially with retardation effects.

 

[berkeman]

How near each other? What frequencies? Sounds like interacting oscillating electrical dipoles? Can you say what the application is, or would you rather not? Do you have access to any of the COMSOL simulation suite?

 

[bob012345]

How near each other? What frequencies? Sounds like interacting oscillating electrical dipoles? Can you say what the application is, or would you rather not? Do you have access to any of the COMSOL simulation suite?

The application is to explore the retardation effects of the forces between current carrying wires. The two currents will be a quarter period out of phase and the distance will be I believe a half wavelength such that the field and current interaction is in sync on both wires. ie. the forces end up in the same direction. I have no direct access to COMSOL unless they offer a free hobbyist version as some companies do. I think the frequency will be in the microwave regime.

 

[berkeman]

Current carrying wires or antennas or dipoles? It makes a difference. What range of EM field strengths versus the mass of the wires/antennas or the mass & dipole moments?

The more information you can give, the better the responses we can try to provide you.

 

[bob012345]

Current carrying wires or antennas or dipoles? It makes a difference. What range of EM field strengths versus the mass of the wires/antennas or the mass & dipole moments?

The more information you can give, the better the responses we can try to provide you.

Since the purpose is to study this I don't have all the exact answers up front but I would say, current carrying wires, not antenna's or dipoles with on the order of 1 to a few amps of current. Total power ~10-100 Watts. Mass of wires ~grams. Magnetic field strength ~$10^{-5}T$ to $10^{-4}T$. Why is mass important?

 

[berkeman]

Lordy. I have no idea where you are going with this. So you have 100W of AC RF power magically coupled into a 1cm piece of wire and you are asking what forces will be induced on another 1cm piece of wire a few cm away? And this is a schoolwork-type question (even for self-study)?

 

[bob012345]

Lordy. I have no idea where you are going with this. So you have 100W of AC RF power magically coupled into a 1cm of wire and you are asking what forces will be induced on another 1cm piece of wire a few cm away? And this is a schoolwork-type question (even for self-study)?

Sorry, I guess I really do not understand what your point is. Please elaborate. Thanks.

 

[Baluncore]

I am interested in the fields and forces especially with retardation effects.

It sounds to me like you are making a current balance from a parallel wire transmission line where the distance between the lines is great when measured in wavelengths.

A similar concept would be to simulate or measure the physical forces between the parallel dipole elements of a Yagi antenna.

What do you mean by "retardation effects" ?

 

[berkeman]

Sorry, I guess I really do not understand what your point is. Please elaborate. Thanks.

How do you magically couple 100W of TX power into your 1cm TX antenna?

 

[bob012345]

How do you magically couple 100W of TX power into your 1cm TX antenna?

That's not what I mean. I have two circuits where the wires of each come close at some point for some distance to measure the interaction between them. Each wire has an oscillating current. They interact. I want to simulate that.

 

[bob012345]

It sounds to me like you are making a current balance from a parallel wire transmission line where the distance between the lines is great when measured in wavelengths.

Where the distance is ~ wavelengths.

A similar concept would be to simulate or measure the physical forces between the parallel dipole elements of a Yagi antenna.

I'll have to check that out, thanks.

What do you mean by "retardation effects" ?

The finite speed of light. Retarded potentials.

https://www.gaussianwaves.com/2021/10/retarded-potentials/

 

[Baluncore]

The finite speed of light. Retarded potentials.

Are the RF currents on the conducting elements traveling or standing waves.

 

[bob012345]

Are the RF currents on the conducting elements traveling or standing waves.

I want the currents to rise and fall with little variation over the length of the short wire segment if possible. That may imply a standing wave with longer wavelength than the wire segment.

BTW, I think longer wires would work with either as long as the phase relationship was maintained.

 

[Baluncore]

I want the currents to rise and fall with little variation over the length of the short wire segment if possible.

Standing waves will have static current nulls and will need to be tuned to the elements. I don't think that is what you want.

Travelling waves will not have current nodes, but traveling waves will need somewhere to go, such as a dummy load or a long lossy line. The traveling wave is probably easier to model numerically, but harder to fund experimentally due to power consumption.

 

[bob012345]

Standing waves will have static current nulls and will need to be tuned to the elements. I don't think that is what you want.

I just want two current carrying wires with a set phase relationship to each other. It can be a standing wave as long as the current produces a magnetic field that propagates out of the wire like a plain single conductor wire does.

Travelling waves will not have current nodes, but traveling waves will need somewhere to go, such as a dummy load or a long lossy line. The traveling wave is probably easier to model numerically, but harder to fund experimentally due to power consumption.

I'm not seeking research grants for this. I just want to run a few simulations to see if this concept works at all. Any thoughts regarding free software recommendations?

 

[bob012345]

Thanks @berkeman and @Baluncore for your interest and help!

 

[anorlunda]

You did not mention the frequency range. Might you be looking for mutual induction at power frequency rather than a RF antenna?

 

[bob012345]

You did not mention the frequency range. Might you be looking for mutual induction at power frequency rather than a RF antenna?

It would probably have to be around 1 GHZ. I'm looking to model and understand the physical forces of interaction of the lines, cables, wires, whatever and their phases. Similar to the standard example of two current carrying wires but at high frequency. I am asking for simulation software recommendations hopefully available for free. I am not a microwave design expert, I just want to explore an idea I have had which I mentioned in post #5 above and see it it works at all in simulation.

 

[Alatorre]

I'm sorry these posts haven't been very helpful, and instead beat around the bush by asking details about your studies instead of answering your question. The only option I know of is what berkeman said, which was COMSOL. I don't think there's any free software of such quality.

 

[Baluncore]

I am asking for simulation software recommendations hopefully available for free.

You are mixing too many interactions into one model. If the forces do not result in physical movement, then you could solve for all complex currents, using an antenna modelling code such as NEC. Then post process to compute the magnetic fields using FEM, and compute the forces on the conductor currents in the magnetic field.

It might be easier to make a very simple model and do some vector calculus.

For some reason you will not explain why you want to investigate this.
Searching for an impossible goal will finally increase the complexity of the solution beyond the capacity of the reasoning brain. Something must give, you turn to simulation.

There is usually a good reason why a particular configuration or interaction is not employed, or is difficult to simulate. I suspect you have made a false assumption, or missed a critical step in the analysis. Simulation will not compensate for analysis.

 

[bob012345]

You are mixing too many interactions into one model. If the forces do not result in physical movement, then you could solve for all complex currents, using an antenna modelling code such as NEC. Then post process to compute the magnetic fields using FEM, and compute the forces on the conductor currents in the magnetic field.

I don't have a model yet. I want to develop one. Your suggestion is helpful as a process to my goal. Thanks.

It might be easier to make a very simple model and do some vector calculus.

I can do that too. Thanks.

For some reason you will not explain why you want to investigate this.
Searching for an impossible goal will finally increase the complexity of the solution beyond the capacity of the reasoning brain. Something must give, you turn to simulation.

I thought I did explain the purpose of the study in post #5.

There is usually a good reason why a particular configuration or interaction is not employed, or is difficult to simulate. I suspect you have made a false assumption, or missed a critical step in the analysis. Simulation will not compensate for analysis.

Of course that all could be true but all I did was ask for suggestions of free EM simulation software so I don't see the need to make any assumptions beyond that.

 

[Baluncore]

I thought I did explain the purpose of the study in post #5.

The two currents will be a quarter period out of phase and the distance will be I believe a half wavelength such that the field and current interaction is in sync on both wires. ie. the forces end up in the same direction.

That is all too complex for one brain. It seems you are expecting both wires to motor themselves in the same direction which, as a closed system, defies the laws of physics as much as does pulling yourself up by your bootlaces.
Sine*Cosine will be zero, no matter how many ± λ/2 delays are introduced.
Are you designing an anti-gravity levitator ?
or maybe a linear motor that runs along a transmission line ?

 

[berkeman]

Are you designing an anti-gravity levitator ?

The Mentors have been dicsussuing this thread for a while now.

Thread is locked.