# NF for multiple ports in HB-ana

Question asked by TNAKA on Jun 8, 2003
Latest reply on Jun 9, 2003 by TNAKA
Here consider a power divider that consists of three equal resistors with R=50/3.
When I simulate NF of this power divider using SP-ana and HB-ana,
I get following results.

For SP-ana
nf(1)=nf(2)=nf(3)=3.010dB
Sij=0.5 for i != j. Sii=0.0

For HB_NOISE-ana
nf(1)=0.0dB, nf(2)=6.021dB, nf(3)=8.451dB

Here PortZ(1)=PortZ(2)=PortZ(3)=50ohm.
NF result from SP-ana can be explained by a definition of NF
for generalized multiple ports described in the following.
S-Parameter Simulation>Noise Analysis>Calculating Noise Figure

According to a definition of generalized multiple ports NF,
denominator of 3-ports NF is twice compared to
conventional 2-ports NF. So NF result from SP-ana is 3dB not 6dB.

On the other hand, how can I understand results of NF from HB_NOISE ana ?
nf(2)=6.021dB is correct NF as 2-ports NF.
But what do nf(1) and nf(3) mean ?

In MDS's manual, a sentence of "If mixing occurs, the Skj matrix is the large-signal,
single sideband, frequency conversion S-matrix and the same definition
of noise figure may be used." existed.
So if MDS's manual is correct, all nf(k) in HB_NOISE must be consistent with SP-ana.
But there is no such sentence in ADS's manual.

Following is ADS's netlist I used.

Options ResourceUsage=yes UseNutmegFormat=no \

Port:Term1  _net165 0 Num=1 Z=50 Ohm P=polar(dbmtow(0),0) \
Freq=1 GHz Noise=yes Pac=polar(dbmtow(0),0)
Port:Term2  out 0 Num=2 Z=50 Ohm Noise=yes
Port:Term3  _net167 0 Num=3 Z=50 Ohm Noise=yes
R:R1  _net165 _net123 R=50/3 Ohm Noise=yes
R:R2  _net123 out R=50/3 Ohm Noise=yes
R:R3  _net123 _net167 R=50/3 Ohm Noise=yes

S_Param:SP1 CalcS=yes CalcY=no CalcZ=no GroupDelayAperture=1e-4 \
FreqConversion=no FreqConversionPort=1 StatusLevel=2 CalcNoise=yes \
SortNoise=0 BandwidthForNoise=1.0 Hz Freq=100 MHz DevOpPtLevel=0 \
NoiseInputPort=1 NoiseOutputPort=2 \
OutputPlan="SP1_Output"
OutputPlan:SP1_Output Type="Output" UseEquationNestLevel=yes \
EquationNestLevel=2

HB:HB1 MaxOrder=4 Freq=1.0 GHz Order=3 StatusLevel=2 FundOversample=1 \
MaxIters=10 SamanskiiConstant=2 \
Restart=no ArcLevelMaxStep=0.0 MaxStepRatio=100 MaxShrinkage=1.0e-5 \
ArcMaxStep=0.0 UseAllSS_Freqs=yes OutputBudgetIV=no UseKrylov=0 \
DevOpPtLevel=0 UseInFile=no UseOutFile=no KrylovPrec=1 ConvMode=2 \
InputFreq=noisefreq FreqForNoise=100 MHz NoiseInputPort=1 NoiseOutputPort=2 \
PhaseNoise=no SortNoise=0 IncludePortNoise=yes NoisyTwoPort=yes \
BandwidthForNoise=1.0 Hz OutputPlan="HB1_Output"
OutputPlan:HB1_Output Type="Output" UseNodeNestLevel=yes NodeNestLevel=2 \
UseEquationNestLevel=yes EquationNestLevel=2

Options:Options1  Temp=16.85 Tnom=25 TopologyCheck=yes \
ForceS_Params=yes MaxSpectralSize=512 V_RelTol=1e-6 I_RelTol=1e-6 \
GiveAllWarnings=yes MaxWarnings=10 SaveBranchCurrents=no \
OutputInternalNodes=no ForceM_Params=yes \