Go to www.awrcorp.com
Back to search page Click to download printable version of this guide.

Complex Frequency Dependent Resistor (Closed Form): ZFREQ



ZFREQ provides computation of circuit parameters for a general complex resistor whose behavior in the frequency domain is governed by a user-supplied table of real part R and imaginary part X.

Equivalent Circuit


Name Description Unit Type Default
ID Name Text Z1
F Vector of Frequencies at which R, X are specified Frequency 1 GHz
R Vector of R Resistance 50
X Vector of X Resistance 0

Parameter Details

F. Vector of frequencies at which R and X parameters are specified. Frequencies must be sequential and specified in ascending order.

R. Vector of active (real) resistance (see the "Equivalent Circuit" section) specified in project resistance units per meter. You must specify each vector entry at the corresponding frequency entry from frequency vector F.

X. Vector of reactive (imaginary) resistance (see the "Equivalent Circuit" section) specified in project resistance units per meter. Each vector entry must be specified at the corresponding frequency entry from frequency vector F.

Parameter Restrictions and Recommendations

  1. The sizes of vector parameters R and X must be equal to the size of frequency vector F.

  2. To provide sufficient accuracy of interpolation (see the "Implementation Details" section) parameters F, R, and X must contain a reasonable number of data points (typically >=10).

  3. You can specify a vector in three ways:

  • Entered as a right-side value of a model parameter, for example R={100,102,110,113,120}

  • Specified elsewhere in an equation

  • Specified in a column or row of a text file. This provides a convenient and flexible method of specification of R and X parameters in a single location. You can create, for example, a Load.txt file containing space separated columns of R and X. The first column must represent frequency in project units (note that changing the project default frequency units demands manual scaling of frequencies in this file). Import or link this file to your project and name it, for example, ZFREQ1. Now you can specify parameter F as F = Col(datafile("ZFREQ1"),1). The values of vector F are copied to the model from column 1 of the Load.txt file, which was imported under the name ZFREQ1. If you prefer to arrange your data by row, use F = Row(datafile("ZFREQ1"),1).

Implementation Details

Model implementation is based on linear interpolation of R and X parameters at each project evaluation frequency. Interpolation uses user-supplied via parameters look-out tables. If project operational frequency is out of range of frequencies in F, then R and X parameters are extrapolated as constant values equal to the first/last entries of corresponding vectors.


This element does not have an assigned layout cell. You can assign artwork cells to any element. See “Assigning Artwork Cells to Layout of Schematic Elements” for details.

Legal and Trademark Notice