Balun BN43-7051 3.5T
VNWA Common Mode Fixture CMRR
CMRR Fixture Without 10:1 Transformer
VNWA Common Mode Fixture CMRR
SimSmith Balun Model
- LG1 = VNWA measured CMRR With 10:1 Transformer
- LG2 = VNWA measured CMRR WithOut 10:1 Transformer
- L = Model CMRR
- Transformer Leakage Inductance, LLs, adjusted for best CMRR fit
Transformer coefficient of coupling = (118 - 0.2*2)/118 = 0.997
- Parallel capacitance, Cp, adjusted for best CMRR fit
- SimSmith files BN43-7501.zip
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SimSmith Balun RUSE Block
Measure Common Mode Z
VNWA Z Common Mode using S21 Through
VNWA Three Port Fixture
VNA Through Calibration Schematic
VNA Measure Schematic
Three Port Fixture CMRR Plot
- Real Imaginary S21 Files:
BN43-7051-3r5T-3PF-RI-P2.s1p
BN43-7051-3r5T-3PF-RI-P3.s1p
- File "join" is Unix join(1) of two above files
- gnuplot CMRR equation, see reference above:
i = {0,1}
P(a,b) = a+b*i
plot 'join' using ($1):(6+20*log10(abs((P($2,$3)+P($4,$5))/(P($2,$3)-P($4,$5))))) with lines title ""
- 6dB added to CMRR to match above measurements
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Three Port Fixture CMRR SimSmith Model and Plot
- Compare Three Port, Two Port without 10:1 Transformer,
and Model without reactance values, Cp=LLs=0
- SimSmith Files with SS-Balun-Model-3P.ssx:
BN43-7501.zip
- SimSmith Equations:
//Plots
$s21 = Gamma(S21[]); // was converted to Z, convert back to T
$s31 = Gamma(S31[]); // was converted to Z, convert back to T
$sum = $s21+$s31;
$diff = $s21-$s31;
ThreePortCMRR = 6 +20*Log10( Mag($sum/$diff) );
Plot(ThreePortCMRR);
ModelCMRR=10*Log10(L.P);
Plot(ModelCMRR,"dB");
TwoPortCMRR=10*Log10(LG1.P);
Plot(TwoPortCMRR,"dB");
- 6dB added to ThreeportCMRR to match TwoPortCMRR and ModelCMRR;
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Measure Common CMRR with RF Voltmeter
- Setup Oscilloscope for 50Ω input and measure Vrms
- Adjust signal generator for 50Ω output
- Connect generator to oscilloscope and adjust, for example 1.5Vrms
- Using simple centertap load CMRR fixture, connect generator and oscope as in photo
- Measure and record common mode Vrms at several frequencies.
Written to file Oscope.txt in this example.
Oscope.txt file, along SimSmith file SS-Balun-Model-Oscope.ssx, in
BN43-7501.zip
- Compute CMRR dB = 20 * Log10(Vcm/Vin) as in SimSmith example
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SimSmith Window
Example Oscilloscope Vcm Screen Shot
Two Port CMRR with Barrel Adapter Thru and ThruMatch Cal
- VNWA Thru and Thru Match calibration using barrel adapter.
- Same 2 Port DUT as above Oscilloscope photo
- SimSmith comparison of; Two Port Vrms, Two Port S21,
and Three Port S21/S31 methods.
- All files for SS-Balun-Oscope-2Port-BarrelCal.ssx in:
BN43-7501.zip
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SimSmith Window
