S-Parameter Element Options
Option
|
Default Value
|
Description
|
s_element.by_entry
|
0
|
0=Measure error tolerance relative
to the absolute difference between each entry of the fit and the corresponding
entry of the S-parameter data
1=Measure error tolerance relative to the size of
S-parameter matrix entry
|
s_element.cache_state_space
|
1
|
1=Enables caching of the state
space fitting information
0=no caching
|
s_element.causality_check
|
0
|
1=Enable causality checking of
Touchstone data
0=No causality checking
|
s_element.causality_checker_tolerance
|
2.0e-3
|
Maximum tolerable magnitude of
noncausality
|
s_element.column_fit
|
1
|
0=Fit each entry separately, then
combine them at the end
1=Fit one column at a time
2=Do the entire matrix at once, using symmetry if
present
|
s_element.convolution
|
0
|
Sets Nexxim to use convolution
rather than state-space matrices to model the behavior of S-parameter
elements during transient analysis.
0: The state space method is used.
1: Convolution is used. The impulse response
is a piecewise linear waveform, with breakpoints chosen to exactly match
the given frequency-domain data. This setting gives the most accurate
response, but may have passivity violations just above the frequency
band of interest. Convolution=1 is the recommended method. Convolution=2
and 3 are for advanced users.
2: Convolution is used. The impulse response
is a train of impulses in the time domain, given by the inverse Fast
Fourier Transform. This setting yields an impulse response that is accurate
in-band and usually passive. However, the transient waveforms may have
discontimuity effects.
3: Convolution is used. The impulse response
is the linear interpolation of the inverse FFT results. This setting
yields an impulse response with a low probability of passivity violations,
but there is significant filtering towards the top of the frequency
range of the input data.
|
s_element.enforce_causality
|
0
|
1=Perform causality check on Touchstone
data, compute compensation to replace non-causal data with causal reconstruction
estimate
0=No checking or compensation
|
s_element.enforce_passivity
|
0
|
0=No passivity enforcement
1=Enforce the passivity of the state-space model
during transient analysis of S-parameter element using a convex algorithm.
6=Enforce passivity using a perturbation algorithm.
7=Enforce passivity using the Iterated Fitting of
Passivity Violations (IFPV) algorithm
|
s_element.errorif
|
1
|
1 = Reject state-space model if
error is above 10%.
0 = No rejection.
|
s_element.g_to_gnd
|
0
|
Conductance between all terminal
nodes of all S-elements and ground
|
s_element.max_states
|
128
|
Sets the maximum number of states
per entry in the state space formulation
|
s_element.mor
|
0
|
0=No model order reduction (MOR)
1=MOR of entire matrix at once
2=MOR of rows of matrix individually, then final
MOR for the combination
3=MOR of rows of matrix individually, no final MOR
4=MOR of columns of matrix individually, then final
MOR for the combination
5=MOR of columns of matrix individually, no final
MOR
|
s_element.mor_sp
|
0
|
1=Use singular perturbation MOR.
Preserves DC fit.
|
s_element.noisemodel
|
external
|
Noise model used in DC and frequency-domain
analyses (not used for time domain analyses)
external=use external data if present, else use
internal noise model
internal=use internal noise model. External data
is ignored
none=no noise calculation
|
s_element.q_limit
|
1e-4
|
Sets the limit of the quality factor
of poles in the rational fit. The default is 1e4. Limiting the quality
factor can be useful in avoiding overfitting, which can lead to severe
passivity violations. The value should be a positive number greater
than 0.5 (generally much greater).
|
s_element.rational_fitting_iteration_limit
|
2
|
Increasing the limit improves the
fit on certain complicated S-parameter cases, at the cost of extra CPU
time.
|
s_element_reduce
|
0
|
Port reduction. 1=eliminate ports
tied to ground directly. Does not affect unconnected ports or ports
tied to ground through a resistor.
|
s_element.reltol
|
1e-2
|
Relative tolerance for state space
fitting.
|
s_element.test_sss
|
1
|
1 = Test existing .sss file for
goodness of fit with given S-parameter data.
Mainly for internal use
|
s_element.time_domain_s_model
|
0
|
1=Create state-space system in
a frequency-domain analysis like LNA where one is not usually generated.
The state-space system won’t be passive unless s_element.enforce_passivity=1
|
s_element.twa
|
1
|
0=use rational fitting
1=use Ansoft-proprietary algorithm for state-space
fitting
|
s_element.wide_dynamic_range
|
0
|
Set wide_dynamic_range to
1 when the S-parameter data contains a wide dynamic range within single
entries, for example with values around 1 at low frequencies but approaching
10-5 at high frequencies,
and the smallest values must be fitted precisely.
|