Re: [Qucs-help] Question about models with mutual inductances

[jeff m. <wa...@wa...>]

Hi Jerry...

If you ground the bottom side of the input and output, the noise goes away.  I 
also tried connecting the bottom of P1 and P2 to ground through a 10e9 Ohm 
resistor and it worked just as well.

jeff, wa1hco



On 08/06/2013 01:15 AM, Jerry Dunmire wrote:
> Hi,
> I am trying to model a filter that is implemented with a transformer wound
> on a toroid. I am using the Mutual Inductor component in the model and I am
> seeing a lot of 'noise' on the S21_dB value. I can't figure out where the
> noise is coming from and I'm hoping someone on this list can explain what
> is going on or direct me to where should read further.
>
> I have included a simple schematic to illustrate.
>
> ...jerry
>
> xformerTest.sch
> ----------------------------
> <Qucs Schematic 0.0.17>
> <Properties>
>    <View=0,0,975,800,1,0,0>
>    <Grid=10,10,1>
>    <DataSet=xformerTest.dat>
>    <DataDisplay=xformerTest.dpl>
>    <OpenDisplay=1>
>    <Script=xformerTest.m>
>    <RunScript=0>
>    <showFrame=0>
>    <FrameText0=Title>
>    <FrameText1=Drawn By:>
>    <FrameText2=Date:>
>    <FrameText3=Revision:>
> </Properties>
> <Symbol>
> </Symbol>
> <Components>
>    <C C1 1 390 180 17 -26 0 1 "100 pF" 1 "" 0 "neutral" 0>
>    <.SP SP1 1 330 280 0 72 0 0 "log" 1 "1 MHz" 1 "100 MHz" 1 "2001" 1 "no" 0
> "1" 0 "2" 0 "no" 0 "no" 0>
>    <Eqn Eqn1 1 560 300 -23 15 0 0 "S21_dB=dB(S[2,1])" 1 "yes" 0>
>    <MUT Tr1 1 310 170 -29 38 0 0 "0.04 uH" 1 "3 uH" 1 ".9" 1>
>    <Pac P2 1 540 170 18 -26 0 1 "2" 1 "50 Ohm" 1 "0 dBm" 0 "1 MHz" 0 "26.85"
> 0>
>    <Pac P1 1 150 180 18 -26 0 1 "1" 1 "50 Ohm" 1 "0 dBm" 0 "1 MHz" 0 "26.85"
> 0>
> </Components>
> <Wires>
>    <390 130 490 130 "" 0 0 0 "">
>    <390 130 390 150 "" 0 0 0 "">
>    <150 210 150 220 "" 0 0 0 "">
>    <150 220 280 220 "" 0 0 0 "">
>    <280 200 280 220 "" 0 0 0 "">
>    <340 210 390 210 "" 0 0 0 "">
>    <340 200 340 210 "" 0 0 0 "">
>    <340 130 390 130 "" 0 0 0 "">
>    <340 130 340 140 "" 0 0 0 "">
>    <150 140 150 150 "" 0 0 0 "">
>    <150 140 280 140 "" 0 0 0 "">
>    <540 200 540 210 "" 0 0 0 "">
>    <390 210 540 210 "" 0 0 0 "">
>    <490 130 490 140 "" 0 0 0 "">
>    <490 140 540 140 "" 0 0 0 "">
> </Wires>
> <Diagrams>
> </Diagrams>
> <Paintings>
> </Paintings>
> ------------------------------------------------------------------------------
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