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	-