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Resistor, Frequency-Dependent (Netlist Only)

Resistor, Frequency-Dependent (Netlist Only)

Instead of the standard resistor syntax with a specified resistance value, you can define the resistance by an expression involving the frequency, using the syntax given in this section.

Notes

The frequency-dependent resistor is available for use in netlists, but is not supported in the Components window of the Designer Schematic Editor.

Parasitic capacitance is ignored in this implementation.

The frequency-dependent resistor is supported only for frequency-domain analyses such as AC and LNA. Running a time-domain analysis such as TRAN on a circuit including a frequency-dependent resistor is an error.

Frequency-Dependent Resistor Instance Netlist Syntax

The general form for a frequency-dependent resistor instance is:

Rxxxx n1 n2 [modelname] [R=]'freq-dependent-expr'

[[TC1=]val] [[TC2=]val] [M=val] [SCALE=val]

[TRAN_EVAL_FREQ=val]

n1 is the positive node and n2 is the negative node of the resistor. The current is assumed to flow from n1 through the resistor to n2. If a model statement is provided for the resistor, the modelname is its name. The modelname is identified by matching it to the .MODEL statements in the netlist.

The frequency-dependent expression should be enclosed in single quotation marks. The token HERTZ can be used in the expression to indicate the frequency as supplied by the analysis. The circuit frequency is available to the model each time the model equations are evaluated. The label R= is optional. The first unlabeled value after a modelname is taken to be the resistance.

The syntax above shows the labels TC1= and TC2= as optional, but this option depends on the presence or absence of the resistance value, labeled or unlabeled:

• When both modelname and the resistance value are present but the resistance value does not have the R= label, the next two unlabeled values are taken to be TC1, then TC2. To specify a value for TC2, either a value for TC1 must be given as well, or the label TC2= must be used.

• When the resistance value is present with the R= label, the labels TC1= and TC2= are required.

When the parameter TRAN_EVAL_FREQ is provided, Nexxim can run a transient (time-domain) analysis, substituting the value of TRAN_EVAL_FREQ for the variable HERTZ to produce a constant resistance value for the transient analysis.

**Frequency-Dependent Resistor Instance Parameters**
Instance Parameter	Description	Unit	Default
L	Resistor length	Meter	0.0
M	Multiplier: simulates parallel resistors	None	1.0
R	Resistance	Ohm	Calculated from geometry or set to RES (model parameter)
SCALE	Scale factor for resistance	None	1.0
TC1	Linear temperature coefficient	°K^-1	TC1R (model parameter)
TC2	Quadratic temperature coefficient	°K^-2	TC2R (model parameter)
TRAN_EVAL_FREQ	Frequency to use for transient analysis	Hertz	0.0
W	Resistor width	Meter	0.0

Frequency-Dependent Resistor Instance Netlist Examples

Frequency-domain analysis:

R1 1 2 resistor1 R='1e-9*HERTZ + 50' dtemp=30
.LNA POI 4 -1e9 -1e6 1e6 1e9

Frequency-domain analysis:

R1 1 2 resistor1 R='1e-9*HERTZ + 50' TRAN_EVAL_FREQ=50e9
.TRAN 0.01ns 10ns

Frequency-Dependent Resistor Model

The model netlist syntax and parameters for the frequency-dependent resistor are identical to those for the standard resistor (see Resistor Model).

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