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10-10-2019
04:04 PM

10-10-2019
04:04 PM

Re: Foster to Cauer Conversion

Hang on a little more.

It's not completely lost, even for Mathcad 15.

Note that the function NUmDen2Cauer, which does most of the work, does NOT use symbolics. It just needs the coefficients of the Numerator and the Denominator polynomes. How it gets it (or, how you get them in there) is another matter. In my (Mathcad 11) case it is essentially what Foster2Cauer does, just before it calls NumDen2Cauer.

Most important at this time is to find the error that is apparently in NumDen2Cauer. I didn't find it yet.

For implementation of that function I used this source: https://nl.mathworks.com/matlabcentral/fileexchange/48042-foster-and-cauer-equivalent-networks (under the "Function" tab). I'm not fluent in Matlab: I may have made a mistake in my implementation, or there is a mistake in that algorithm.

Luc

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10-10-2019
04:52 PM

10-10-2019
04:52 PM

Re: Foster to Cauer Conversion

In the file attached, I tried to write the program and if fails when I insert the command to extract the coefficients:

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10-10-2019
05:07 PM

10-10-2019
05:07 PM

Re: Foster to Cauer Conversion

Attached is the same file but saved as MathCAd 11

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10-10-2019
05:46 PM

10-10-2019
05:46 PM

Re: Foster to Cauer Conversion

I had done work on routines for impedance manipulation some time ago (as may be seen in the age of some of the included functions), when I was also working on thermal models. I cleaned an old file that did the desired conversion so it is self contained. Only a few of the polynomial functions are needed, but I left them all in case others may be interested. I have not reviewed the main impedance programs; they are what I had done some years ago.

This is a v11 program - I'm one of the remaining users keeping an old PC going just for this reason. It should work in v15, since the routines are numeric and don't depend on symbolics, except for a few simple function examples.

It gives the same answer for the 8th order as the NXP paper.

Lou

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10-10-2019
05:48 PM

10-10-2019
05:48 PM

Re: Foster to Cauer Conversion

For some reason, I couldn't add a second attachment in the previous post Here's a pdf, but it doesn't show the heavy lifting.

Lou

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10-10-2019
05:59 PM

10-10-2019
05:59 PM

Re: Foster to Cauer Conversion

See if this works better.

Note: You ARE able to get arrays with the coefficients of the numerator and the denominator. That should be all that is required. As I said. The important work is done in the NumDen2Cauer() function, which only requires the two arrays with coefficients...

Luc

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10-10-2019
06:08 PM

10-10-2019
06:08 PM

Re: Foster to Cauer Conversion

Nice Lou !

I guess you've solved the problem of the OP, if the files runs in Mathcad 15 as well.

Luc

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10-11-2019
10:05 AM

10-11-2019
10:05 AM

Re: Foster to Cauer Conversion

Luc,

Can you post the v11 program that has your NumDen2Cauer() function?

Probably a brain freeze, but not sure I understand what you mean by OP.

Lou

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10-11-2019
10:47 AM

10-11-2019
10:47 AM

Re: Foster to Cauer Conversion

Hi Luc,

This produces an internal error:

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10-11-2019
10:53 AM

10-11-2019
10:53 AM

Re: Foster to Cauer Conversion

Hi Luc,

Is it possible that your result goes off because the subtraction

does not cancel completely the largest exponent.

I had that problem and here is what I did: