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8.4.5 Uniform Distributed RC Model (URC)

The URC model is derived from a model proposed by L. Gertzberrg in 1974. The model is accomplished by a subcircuit type expansion of the URC line into a network of lumped RC segments with internally generated nodes. The RC segments are in a geometric progression, increasing toward the middle of the URC line, with K as a proportionality constant. The number of lumped segments used, if not specified for the URC line device, is determined by the following formula:

                                            2
                    |     R C        |(K-1)|  |
                          _ _      2
                 log|F        2 J L  |-----|  |
                      max
                    |     L L        |  K  |  |
     
            N =  ------------------------------
                                  log K

The URC line is made up strictly of resistor and capacitor segments unless the ISPERL parameter is given a nonzero value, in which case the capacitors are replaced with reverse biased diodes with a zero-bias junction capacitance equivalent to the capacitance replaced, and with a saturation current of ISPERL amps per meter of transmission line and an optional series resistance equivalent to RSPERL ohms per meter.

name parameter units default example
K Propagation Constant - 2.0 1.2
FMAX Maximum Frequency of interest Hz 1.0G 6.5Meg
RPERL Resistance per unit length Z/m 1000 10
CPERL Capacitance per unit length F/m 1.0e-15 1pF
ISPERL Saturation Current per unit length A/m 0 -
RSPERL Diode Resistance per unit length Z/m 0 -