rautio
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Re: Quick question: why does Q of spiral inductor have a pea
Hi Jian -- Glad to hear that you might be willing to put some effort into this topic. From your last post, I thought you were backing out. However, keep in mind that I will be inclined to not proceed if you keep saying, "It's accurate, it's accurate!" when our objective is to find the error. Also, you may recall that I wrote that claiming to be an expert or an authority (which you have done again in the above post) is not helpful. Allow me to explain. Many people in the US (and Europe, too), especially of my generation, were brought up to very strongly distrust experts and authority. And I mean VERY strongly. Thus, when you offer being an expert as part of the defense for your viewpoint, it actually makes your case much weaker. If you would like to make a strong case, you should not draw attention to being an expert. You should place your emphasis on data.
As for point #1, when I say the differences appear large, I am pointing out that two people can look at exactly the same data and see two completely different things, and both can be completely 100% correct. This is a very important concept you would do well to realize is often the case. It is my nature to look for differences in data because that is where the interesting research can be done. So I look at your data, or anyone else's data, I look for the differences. The differences between triangle and rectangle meshing results in your plots are quite easy to see. That is something, if I had the software, that I could work with. Trying to find out why those differences are there could be a lot of fun, as well as educational. However, if we look at that data and say it has good agreement, that is the end of the story. Nothing more to do! Soooo boring!
So assuming, we won't rely on telling each other that we're experts, and assuming we're looking for the error, and that we are not successful until we find a reasonably high confidence number for the error, here are the answers to your questions:
1) Purpose? To find the error in inductance at low frequency.
2) For whom? For curiosity primarily, others may find it interesting or even useful, but I consider that secondary. If you want to do something of immediate practicality, you should look elsewhere.
3) What is low freq? Anything where the current density is close to uniform through the volume of the metal. There are two transition frequencies for microstrip loss, as indicated in my paper on microstrip loss. High frequency is above the higher of the two. Low frequency is below the lower of the two.
4) Yes, DC is low frequency. However, DC is a different problem as the ground plane and any sidewalls have no effect on magneto static inductance. Would be interesting to get a result there. If you can do that, please share it with us.
5) What is the converged value? An example is in the pdf I attached previously.
6) Box size? Given in the pdf I attached previously. You should be able to download SonnetLite and look at the two layer file. All the info is in there, too.
7-12) All box boundaries in this case are infinitely thick and perfect conductor. Top and bottom covers can be lossy and of any thickness but are not in this case. Sidewalls are always PEC as I often state.
Extra comment for 10) Yes we can not get perfect PEC walls in measurement. However, all computer modeling is abstraction from reality. Thus all EM analyses always give the wrong answer. We can never build anything exactly as we analyze it. We can only approximate it. Fortunately, in the case of PEC walls and in the case of many other things that we approximate, we can often get really really close. (I think you know this.)
You can do the multi-sheet model manually, it might be interesting to see if you can duplicate what I did in the previously attached pdf.
Just for the record, I will state my top level viewpoint on this matter, even though I have already done so many times. All the different EM tools (and their models, including both tube-like thickness and multi-sheet thickness) have their advantages and disadvantages and a good designer can benefit tremendously from intelligent use of multiple tools and models. And that includes tools from multiple vendors. I will take issue with anyone that seriously suggests anything to the contrary with regard to any of the available models or any of the available EM tools. I do not consider "puffing" (a standard term of the sales trade) to be serious.
Hi Jian -- Glad to hear that you might be willing to put some effort into this topic. From your last post, I thought you were backing out. However, keep in mind that I will be inclined to not proceed if you keep saying, "It's accurate, it's accurate!" when our objective is to find the error. Also, you may recall that I wrote that claiming to be an expert or an authority (which you have done again in the above post) is not helpful. Allow me to explain. Many people in the US (and Europe, too), especially of my generation, were brought up to very strongly distrust experts and authority. And I mean VERY strongly. Thus, when you offer being an expert as part of the defense for your viewpoint, it actually makes your case much weaker. If you would like to make a strong case, you should not draw attention to being an expert. You should place your emphasis on data.
As for point #1, when I say the differences appear large, I am pointing out that two people can look at exactly the same data and see two completely different things, and both can be completely 100% correct. This is a very important concept you would do well to realize is often the case. It is my nature to look for differences in data because that is where the interesting research can be done. So I look at your data, or anyone else's data, I look for the differences. The differences between triangle and rectangle meshing results in your plots are quite easy to see. That is something, if I had the software, that I could work with. Trying to find out why those differences are there could be a lot of fun, as well as educational. However, if we look at that data and say it has good agreement, that is the end of the story. Nothing more to do! Soooo boring!
So assuming, we won't rely on telling each other that we're experts, and assuming we're looking for the error, and that we are not successful until we find a reasonably high confidence number for the error, here are the answers to your questions:
1) Purpose? To find the error in inductance at low frequency.
2) For whom? For curiosity primarily, others may find it interesting or even useful, but I consider that secondary. If you want to do something of immediate practicality, you should look elsewhere.
3) What is low freq? Anything where the current density is close to uniform through the volume of the metal. There are two transition frequencies for microstrip loss, as indicated in my paper on microstrip loss. High frequency is above the higher of the two. Low frequency is below the lower of the two.
4) Yes, DC is low frequency. However, DC is a different problem as the ground plane and any sidewalls have no effect on magneto static inductance. Would be interesting to get a result there. If you can do that, please share it with us.
5) What is the converged value? An example is in the pdf I attached previously.
6) Box size? Given in the pdf I attached previously. You should be able to download SonnetLite and look at the two layer file. All the info is in there, too.
7-12) All box boundaries in this case are infinitely thick and perfect conductor. Top and bottom covers can be lossy and of any thickness but are not in this case. Sidewalls are always PEC as I often state.
Extra comment for 10) Yes we can not get perfect PEC walls in measurement. However, all computer modeling is abstraction from reality. Thus all EM analyses always give the wrong answer. We can never build anything exactly as we analyze it. We can only approximate it. Fortunately, in the case of PEC walls and in the case of many other things that we approximate, we can often get really really close. (I think you know this.)
You can do the multi-sheet model manually, it might be interesting to see if you can duplicate what I did in the previously attached pdf.
Just for the record, I will state my top level viewpoint on this matter, even though I have already done so many times. All the different EM tools (and their models, including both tube-like thickness and multi-sheet thickness) have their advantages and disadvantages and a good designer can benefit tremendously from intelligent use of multiple tools and models. And that includes tools from multiple vendors. I will take issue with anyone that seriously suggests anything to the contrary with regard to any of the available models or any of the available EM tools. I do not consider "puffing" (a standard term of the sales trade) to be serious.